path: root/src/mongo/shell/replsettest.js

/**
 * Sets up a replica set. To make the set running, call {@link #startSet},
 * followed by {@link #initiate} (and optionally,
 * {@link #awaitSecondaryNodes} to block till the  set is fully operational).
 * Note that some of the replica start up parameters are not passed here,
 * but to the #startSet method.
 *
 * @param {Object|string} opts If this value is a string, it specifies the connection string for
 *      a MongoD host to be used for recreating a ReplSetTest from. Otherwise, if it is an object,
 *      it must have the following contents:
 *
 *   {
 *     name {string}: name of this replica set. Default: 'testReplSet'
 *     host {string}: name of the host machine. Hostname will be used
 *        if not specified.
 *     useHostName {boolean}: if true, use hostname of machine,
 *        otherwise use localhost
 *     nodes {number|Object|Array.<Object>}: number of replicas. Default: 0.
 *        Can also be an Object (or Array).
 *        Format for Object:
 *          {
 *            <any string>: replica member option Object. @see MongoRunner.runMongod
 *            <any string2>: and so on...
 *          }
 *          If object has a special "rsConfig" field then those options will be used for each
 *          replica set member config options when used to initialize the replica set, or
 *          building the config with getReplSetConfig()
 *
 *        Format for Array:
 *           An array of replica member option Object. @see MongoRunner.runMongod
 *
 *        Note: For both formats, a special boolean property 'arbiter' can be
 *          specified to denote a member is an arbiter.
 *
 *        Note: A special "bridgeOptions" property can be specified in both the object and array
 *           formats to configure the options for the mongobridge corresponding to that node. These
 *           options are merged with the opts.bridgeOptions options, where the node-specific options
 *           take precedence.
 *
 *     nodeOptions {Object}: Command-line options to apply to all nodes in the replica set.
 *        Format for Object:
 *          { cmdline-param-with-no-arg : "",
 *            param-with-arg : arg }
 *        This turns into "mongod --cmdline-param-with-no-arg --param-with-arg arg"
 *
 *     causallyConsistent {boolean}: Specifies whether the connections to the replica set nodes
 *        should be created with the 'causal consistency' flag enabled, which means they will gossip
 *        the cluster time and add readConcern afterClusterTime where applicable. Defaults to false.
 *
 *     oplogSize {number}: Default: 40
 *     useSeedList {boolean}: Use the connection string format of this set
 *        as the replica set name (overrides the name property). Default: false
 *     keyFile {string}
 *     protocolVersion {number}: protocol version of replset used by the replset initiation.
 *
 *     useBridge {boolean}: If true, then a mongobridge process is started for each node in the
 *        replica set. Both the replica set configuration and the connections returned by startSet()
 *        will be references to the proxied connections. Defaults to false.
 *
 *     bridgeOptions {Object}: Options to apply to all mongobridge processes. Defaults to {}.
 *
 *     settings {object}: Setting used in the replica set config document.
 *        Example:
 *              settings: { chainingAllowed: false, ... }
 *   }
 *
 * Member variables:
 *  nodes {Array.<Mongo>} - connection to replica set members
 */

var ReplSetTest = function(opts) {
    'use strict';

    if (!(this instanceof ReplSetTest)) {
        return new ReplSetTest(opts);
    }

    // Capture the 'this' reference
    var self = this;

    // Replica set health states
    var Health = {UP: 1, DOWN: 0};

    var _alldbpaths;
    var _configSettings;

    // mongobridge related variables. Only available if the bridge option is selected.
    var _useBridge;
    var _bridgeOptions;
    var _unbridgedPorts;
    var _unbridgedNodes;
    var _allocatePortForNode;
    var _allocatePortForBridge;

    var _causalConsistency;

    // Some code still references kDefaultTimeoutMS as a (non-static) member variable, so make sure
    // it's still accessible that way.
    this.kDefaultTimeoutMS = ReplSetTest.kDefaultTimeoutMS;
    var oplogName = 'oplog.rs';

    // Publicly exposed variables

    /**
     * Returns the config document reported from the specified connection.
     */
    function _replSetGetConfig(conn) {
        return assert.commandWorked(conn.adminCommand({replSetGetConfig: 1})).config;
    }

    /**
     * Invokes the 'ismaster' command on each individual node and returns the current primary, or
     * false if none is found. Populates the following cached values:
     * '_master': the current primary
     * '_slaves': all nodes other than 'master' (note this includes arbiters)
     * '_liveNodes': all currently reachable nodes
     */
    function _callIsMaster() {
        self._liveNodes = [];
        self._master = null;
        self._slaves = [];

        var twoPrimaries = false;
        self.nodes.forEach(function(node) {
            try {
                node.setSlaveOk();
                var n = node.getDB('admin').runCommand({ismaster: 1});
                self._liveNodes.push(node);
                if (n.ismaster == true) {
                    if (self._master) {
                        twoPrimaries = true;
                    } else {
                        self._master = node;
                    }
                } else {
                    self._slaves.push(node);
                }
            } catch (err) {
                print("ReplSetTest Could not call ismaster on node " + node + ": " + tojson(err));
                self._slaves.push(node);
            }
        });
        if (twoPrimaries) {
            return false;
        }

        return self._master || false;
    }

    /**
     * Attempt to connect to all nodes and returns a list of slaves in which the connection was
     * successful.
     */
    function _determineLiveSlaves() {
        _callIsMaster();
        return self._slaves.filter(function(n) {
            return self._liveNodes.indexOf(n) !== -1;
        });
    }

    function asCluster(conn, fn, keyFileParam = self.keyFile) {
        if (keyFileParam) {
            return authutil.asCluster(conn, keyFileParam, fn);
        } else {
            return fn();
        }
    }

    /**
     * Returns 'true' if the "conn" has been configured to run without journaling enabled.
     */
    function _isRunningWithoutJournaling(conn) {
        var result = asCluster(conn, function() {
            var serverStatus = assert.commandWorked(conn.adminCommand({serverStatus: 1}));
            if (serverStatus.storageEngine.hasOwnProperty('persistent')) {
                if (!serverStatus.storageEngine.persistent) {
                    return true;
                }
            } else if (serverStatus.storageEngine.name == 'inMemory' ||
                       serverStatus.storageEngine.name == 'ephemeralForTest') {
                return true;
            }
            var cmdLineOpts = assert.commandWorked(conn.adminCommand({getCmdLineOpts: 1}));
            var getWithDefault = function(dict, key, dflt) {
                if (dict[key] === undefined)
                    return dflt;
                return dict[key];
            };
            return !getWithDefault(
                getWithDefault(getWithDefault(cmdLineOpts.parsed, "storage", {}), "journal", {}),
                "enabled",
                true);
        });
        return result;
    }

    /**
     * Wait for a rs indicator to go to a particular state or states.
     *
     * @param node is a single node or list of nodes, by id or conn
     * @param states is a single state or list of states
     * @param ind is the indicator specified
     * @param timeout how long to wait for the state to be reached
     * @param reconnectNode indicates that we should reconnect to a node that stepped down
     */
    function _waitForIndicator(node, states, ind, timeout, reconnectNode) {
        timeout = timeout || self.kDefaultTimeoutMS;
        if (reconnectNode === undefined) {
            reconnectNode = true;
        }

        if (node.length) {
            var nodes = node;
            for (var i = 0; i < nodes.length; i++) {
                if (states.length)
                    _waitForIndicator(nodes[i], states[i], ind, timeout, reconnectNode);
                else
                    _waitForIndicator(nodes[i], states, ind, timeout, reconnectNode);
            }

            return;
        }

        if (!node.getDB) {
            node = self.nodes[node];
        }

        if (!states.length) {
            states = [states];
        }

        print("ReplSetTest waitForIndicator " + ind + " on " + node);
        printjson(states);
        print("ReplSetTest waitForIndicator from node " + node);

        var lastTime = null;
        var currTime = new Date().getTime();
        var status;

        let foundState;
        assert.soon(function() {
            try {
                var conn = _callIsMaster();
                if (!conn) {
                    conn = self._liveNodes[0];
                }

                // Try again to load connection
                if (!conn)
                    return false;

                asCluster(conn, function() {
                    status = conn.getDB('admin').runCommand({replSetGetStatus: 1});
                });
            } catch (ex) {
                print("ReplSetTest waitForIndicator could not get status: " + tojson(ex));
                return false;
            }

            var printStatus = false;
            if (lastTime == null || (currTime = new Date().getTime()) - (1000 * 5) > lastTime) {
                if (lastTime == null) {
                    print("ReplSetTest waitForIndicator Initial status (timeout : " + timeout +
                          ") :");
                }

                printjson(status);
                lastTime = new Date().getTime();
                printStatus = true;
            }

            if (typeof status.members == 'undefined') {
                return false;
            }

            for (var i = 0; i < status.members.length; i++) {
                if (printStatus) {
                    print("Status for : " + status.members[i].name + ", checking " + node.host +
                          "/" + node.name);
                }

                if (status.members[i].name == node.host || status.members[i].name == node.name) {
                    for (var j = 0; j < states.length; j++) {
                        if (printStatus) {
                            print("Status -- " +
                                  " current state: " + status.members[i][ind] +
                                  ",  target state : " + states[j]);
                        }

                        if (typeof (states[j]) != "number") {
                            throw new Error("State was not an number -- type:" +
                                            typeof (states[j]) + ", value:" + states[j]);
                        }
                        if (status.members[i][ind] == states[j]) {
                            foundState = states[j];
                            return true;
                        }
                    }
                }
            }

            return false;
        }, "waiting for state indicator " + ind + " for " + timeout + "ms", timeout);

        // If we were waiting for the node to step down, wait until we can connect to it again,
        // since primaries close external connections upon stepdown. This ensures that the
        // connection to the node is usable after the function returns.
        if (reconnectNode && foundState === ReplSetTest.State.SECONDARY) {
            assert.soon(function() {
                try {
                    node.getDB("foo").bar.stats();
                    return true;
                } catch (e) {
                    return false;
                }
            }, "timed out waiting to reconnect to node " + node.name);
        }

        print("ReplSetTest waitForIndicator final status:");
        printjson(status);
    }

    /**
     * Wait for a health indicator to go to a particular state or states.
     *
     * @param node is a single node or list of nodes, by id or conn
     * @param state is a single state or list of states. ReplSetTest.Health.DOWN can
     *     only be used in cases when there is a primary available or slave[0] can
     *     respond to the isMaster command.
     */
    function _waitForHealth(node, state, timeout) {
        _waitForIndicator(node, state, "health", timeout);
    }

    /**
     * Returns true if the OpTime is empty, else false.
     *
     * Empty OpTime Formats:
     *   PV0: Timestamp(0,0)
     *   PV1: {ts: Timestamp(0,0), t: NumberLong(-1)}
     */
    function _isEmptyOpTime(opTime) {
        if (!opTime.hasOwnProperty("ts") || !opTime.hasOwnProperty("t")) {
            return (opTime.getTime() == 0 && opTime.getInc() == 0);
        }
        return (opTime.ts.getTime() == 0 && opTime.ts.getInc() == 0 && opTime.t == -1);
    }

    /**
     * Returns the OpTime for the specified host by issuing replSetGetStatus.
     */
    function _getLastOpTime(conn) {
        var replSetStatus =
            assert.commandWorked(conn.getDB("admin").runCommand({replSetGetStatus: 1}));
        var connStatus = replSetStatus.members.filter(m => m.self)[0];
        var opTime = connStatus.optime;
        if (_isEmptyOpTime(opTime)) {
            throw new Error("last OpTime is empty -- connection: " + conn);
        }
        return opTime;
    }

    /**
     * Returns the {readConcern: majority} OpTime for the host.
     * This is the OpTime of the host's "majority committed" snapshot.
     * This function may return an OpTime with Timestamp(0,0) and Term(0) if read concern majority
     * is not enabled, or if there has not been a committed snapshot yet.
     */
    function _getReadConcernMajorityOpTime(conn) {
        var replSetStatus =
            assert.commandWorked(conn.getDB("admin").runCommand({replSetGetStatus: 1}));
        return (replSetStatus.OpTimes || replSetStatus.optimes).readConcernMajorityOpTime ||
            {ts: Timestamp(0, 0), t: NumberLong(0)};
    }

    /**
     * Returns the {readConcern: majority} OpTime for the host. Throws if not available.
     */
    this.getReadConcernMajorityOpTimeOrThrow = function(conn) {
        const majorityOpTime = _getReadConcernMajorityOpTime(conn);
        if (friendlyEqual(majorityOpTime, {ts: Timestamp(0, 0), t: NumberLong(0)})) {
            throw new Error("readConcern majority optime not available");
        }
        return majorityOpTime;
    };

    /**
     * Returns the last durable OpTime for the host if running with journaling.
     * Returns the last applied OpTime otherwise.
     */
    function _getDurableOpTime(conn) {
        var replSetStatus =
            assert.commandWorked(conn.getDB("admin").runCommand({replSetGetStatus: 1}));

        var opTimeType = "durableOpTime";
        if (_isRunningWithoutJournaling(conn)) {
            opTimeType = "appliedOpTime";
        }
        var opTime = replSetStatus.optimes[opTimeType];
        if (_isEmptyOpTime(opTime)) {
            throw new Error("last durable OpTime is empty -- connection: " + conn);
        }
        return opTime;
    }

    /*
     * Compares Timestamp objects. Returns true if ts1 is 'earlier' than ts2, else false.
     */
    function _isEarlierTimestamp(ts1, ts2) {
        if (ts1.getTime() == ts2.getTime()) {
            return ts1.getInc() < ts2.getInc();
        }
        return ts1.getTime() < ts2.getTime();
    }

    /*
     * Returns true if the node can be elected primary of a replica set.
     */
    function _isElectable(node) {
        return !node.arbiterOnly && (node.priority === undefined || node.priority != 0);
    }

    /**
     * Returns list of nodes as host:port strings.
     */
    this.nodeList = function() {
        var list = [];
        for (var i = 0; i < this.ports.length; i++) {
            list.push(this.host + ":" + this.ports[i]);
        }

        return list;
    };

    this.getNodeId = function(node) {
        if (node.toFixed) {
            return parseInt(node);
        }

        for (var i = 0; i < this.nodes.length; i++) {
            if (this.nodes[i] == node) {
                return i;
            }
        }

        if (node instanceof ObjectId) {
            for (i = 0; i < this.nodes.length; i++) {
                if (this.nodes[i].runId == node) {
                    return i;
                }
            }
        }

        if (node.nodeId != null) {
            return parseInt(node.nodeId);
        }

        return undefined;
    };

    this.getPort = function(n) {
        var n = this.getNodeId(n);
        return this.ports[n];
    };

    this.getDbPath = function(node) {
        // Get a replica set node (check for use of bridge).
        const n = this.getNodeId(node);
        const replNode = _useBridge ? _unbridgedNodes[n] : this.nodes[n];
        return replNode.dbpath;
    };

    this._addPath = function(p) {
        if (!_alldbpaths)
            _alldbpaths = [p];
        else
            _alldbpaths.push(p);

        return p;
    };

    this.getReplSetConfig = function() {
        var cfg = {};
        cfg._id = this.name;
        cfg.protocolVersion = 1;

        cfg.members = [];

        for (var i = 0; i < this.ports.length; i++) {
            var member = {};
            member._id = i;

            member.host = this.host;
            if (!member.host.includes('/')) {
                member.host += ":" + this.ports[i];
            }

            var nodeOpts = this.nodeOptions["n" + i];
            if (nodeOpts) {
                if (nodeOpts.arbiter) {
                    member.arbiterOnly = true;
                }

                if (nodeOpts.rsConfig) {
                    Object.extend(member, nodeOpts.rsConfig);
                }
            }

            cfg.members.push(member);
        }

        if (_configSettings) {
            cfg.settings = _configSettings;
        }

        return cfg;
    };

    this.getURL = function() {
        var hosts = [];

        for (var i = 0; i < this.ports.length; i++) {
            hosts.push(this.host + ":" + this.ports[i]);
        }

        return this.name + "/" + hosts.join(",");
    };

    /**
     * Starts each node in the replica set with the given options.
     *
     * @param options - The options passed to {@link MongoRunner.runMongod}
     */
    this.startSet = function(options, restart) {
        print("ReplSetTest starting set");

        if (options && options.keyFile) {
            self.keyFile = options.keyFile;
        }

        if (options) {
            self.startOptions = options;
        }

        var nodes = [];
        for (var n = 0; n < this.ports.length; n++) {
            nodes.push(this.start(n, options, restart));
        }

        this.nodes = nodes;
        return this.nodes;
    };

    /**
     * Blocks until the secondary nodes have completed recovery and their roles are known. Blocks on
     * all secondary nodes or just 'slaves', if specified.
     */
    this.awaitSecondaryNodes = function(timeout, slaves) {
        timeout = timeout || self.kDefaultTimeoutMS;

        assert.soonNoExcept(function() {
            // Reload who the current slaves are
            self.getPrimary(timeout);

            var slavesToCheck = slaves || self._slaves;
            var len = slavesToCheck.length;
            var ready = true;

            for (var i = 0; i < len; i++) {
                var isMaster = slavesToCheck[i].getDB("admin").runCommand({ismaster: 1});
                var arbiter = (isMaster.arbiterOnly == undefined ? false : isMaster.arbiterOnly);
                ready = ready && (isMaster.secondary || arbiter);
            }

            return ready;
        }, "Awaiting secondaries", timeout);
    };

    /**
     * Blocks until the specified node says it's syncing from the given upstream node.
     */
    this.awaitSyncSource = function(node, upstreamNode, timeout) {
        print("Waiting for node " + node.name + " to start syncing from " + upstreamNode.name);
        var status = null;
        assert.soonNoExcept(
            function() {
                status = node.getDB("admin").runCommand({replSetGetStatus: 1});
                for (var j = 0; j < status.members.length; j++) {
                    if (status.members[j].self) {
                        return status.members[j].syncingTo === upstreamNode.host;
                    }
                }
                return false;
            },
            "Awaiting node " + node + " syncing from " + upstreamNode + ": " + tojson(status),
            timeout);
    };

    /**
     * Blocks until each node agrees that all other nodes have applied the most recent oplog entry.
     */
    this.awaitNodesAgreeOnAppliedOpTime = function(timeout, nodes) {
        timeout = timeout || self.kDefaultTimeoutMS;
        nodes = nodes || self.nodes;

        assert.soon(function() {
            let appliedOpTimeConsensus = undefined;
            for (let i = 0; i < nodes.length; i++) {
                let replSetGetStatus;
                try {
                    replSetGetStatus = nodes[i].adminCommand({replSetGetStatus: 1});
                } catch (e) {
                    print("AwaitNodesAgreeOnAppliedOpTime: Retrying because node " + nodes[i].name +
                          " failed to execute replSetGetStatus: " + tojson(e));
                    return false;
                }
                assert.commandWorked(replSetGetStatus);

                if (appliedOpTimeConsensus === undefined) {
                    if (replSetGetStatus.optimes) {
                        appliedOpTimeConsensus = replSetGetStatus.optimes.appliedOpTime;
                    } else {
                        // Older versions of mongod do not include an 'optimes' field in the
                        // replSetGetStatus response. We instead pull an optime from the first
                        // replica set member that includes one in its status. All we need here is
                        // any initial value that we can compare to all the other optimes.
                        let optimeMembers = replSetGetStatus.members.filter(m => m.optime);
                        assert(optimeMembers.length > 0,
                               "AwaitNodesAgreeOnAppliedOpTime: replSetGetStatus did not " +
                                   "include optimes for any members: " + tojson(replSetGetStatus));
                        appliedOpTimeConsensus = optimeMembers[0].optime;
                    }

                    assert(appliedOpTimeConsensus,
                           "AwaitNodesAgreeOnAppliedOpTime: missing appliedOpTime in " +
                               "replSetGetStatus: " + tojson(replSetGetStatus));
                }

                if (replSetGetStatus.optimes &&
                    !friendlyEqual(replSetGetStatus.optimes.appliedOpTime,
                                   appliedOpTimeConsensus)) {
                    print("AwaitNodesAgreeOnAppliedOpTime: Retrying because node " + nodes[i].name +
                          " has appliedOpTime " + tojson(replSetGetStatus.optimes.appliedOpTime) +
                          " that does not match the previously observed appliedOpTime " +
                          tojson(appliedOpTimeConsensus));
                    return false;
                }

                for (let j = 0; j < replSetGetStatus.members.length; j++) {
                    if (replSetGetStatus.members[j].state == ReplSetTest.State.ARBITER) {
                        // ARBITER nodes do not apply oplog entries and do not have an 'optime'
                        // field.
                        continue;
                    }

                    if (!friendlyEqual(replSetGetStatus.members[j].optime,
                                       appliedOpTimeConsensus)) {
                        print("AwaitNodesAgreeOnAppliedOpTime: Retrying because node " +
                              nodes[i].name + " sees optime " +
                              tojson(replSetGetStatus.members[j].optime) + " on node " +
                              replSetGetStatus.members[j].name + " but expects to see optime " +
                              tojson(appliedOpTimeConsensus));
                        return false;
                    }
                }
            }

            print(
                "AwaitNodesAgreeOnAppliedOpTime: All nodes agree that all ops are applied up to " +
                tojson(appliedOpTimeConsensus));
            return true;
        }, "Awaiting nodes to agree that all ops are applied across replica set", timeout);
    };

    this._findHighestPriorityNodes = function(config) {
        let highestPriority = 0;
        let highPriorityNodes = [];
        for (let i = 0; i < config.members.length; i++) {
            const member = config.members[i];
            if (member.priority > highestPriority) {
                highestPriority = member.priority;
                highPriorityNodes = [this.nodes[i]];
            } else if (member.priority === highestPriority) {
                highPriorityNodes.push(this.nodes[i]);
            }
        }
        return highPriorityNodes;
    };

    /**
     * Blocks until the node with the highest priority is the primary.  If there are multiple
     * nodes tied for highest priority, waits until one of them is the primary.
     */
    this.awaitHighestPriorityNodeIsPrimary = function(timeout) {
        timeout = timeout || self.kDefaultTimeoutMS;

        // First figure out the set of highest priority nodes.
        const config = asCluster(this.nodes, () => self.getReplSetConfigFromNode());
        const highPriorityNodes = this._findHighestPriorityNodes(config);

        // Now wait for the primary to be one of the highest priority nodes.
        assert.soon(
            function() {
                return highPriorityNodes.includes(self.getPrimary());
            },
            function() {
                return "Expected primary to be one of: " + tojson(highPriorityNodes) +
                    ", but found primary to be: " + tojson(self.getPrimary());
            },
            timeout);

        // Finally wait for all nodes to agree on the primary.
        this.awaitNodesAgreeOnPrimary(timeout);
        const primary = this.getPrimary();
        assert(highPriorityNodes.includes(primary),
               "Primary switched away from highest priority node.  Found primary: " +
                   tojson(primary) + ", but expected one of: " + tojson(highPriorityNodes));
    };

    /**
     * Blocks until all nodes agree on who the primary is.
     * If 'expectedPrimaryNodeId' is provided, ensure that every node is seeing this node as the
     * primary. Otherwise, ensure that all the nodes in the set agree with the first node on the
     * identity of the primary.
     */
    this.awaitNodesAgreeOnPrimary = function(timeout, nodes, expectedPrimaryNodeId) {
        timeout = timeout || self.kDefaultTimeoutMS;
        nodes = nodes || self.nodes;
        expectedPrimaryNodeId = expectedPrimaryNodeId || -1;
        if (expectedPrimaryNodeId === -1) {
            print("AwaitNodesAgreeOnPrimary: Waiting for nodes to agree on any primary.");
        } else {
            print("AwaitNodesAgreeOnPrimary: Waiting for nodes to agree on " +
                  nodes[expectedPrimaryNodeId].name + " as primary.");
        }

        assert.soonNoExcept(function() {
            var primary = expectedPrimaryNodeId;

            for (var i = 0; i < nodes.length; i++) {
                var replSetGetStatus =
                    assert.commandWorked(nodes[i].getDB("admin").runCommand({replSetGetStatus: 1}));
                var nodesPrimary = -1;
                for (var j = 0; j < replSetGetStatus.members.length; j++) {
                    if (replSetGetStatus.members[j].state === ReplSetTest.State.PRIMARY) {
                        // Node sees two primaries.
                        if (nodesPrimary !== -1) {
                            print("AwaitNodesAgreeOnPrimary: Retrying because " + nodes[i].name +
                                  " thinks both " + nodes[nodesPrimary].name + " and " +
                                  nodes[j].name + " are primary.");

                            return false;
                        }
                        nodesPrimary = j;
                    }
                }
                // Node doesn't see a primary.
                if (nodesPrimary < 0) {
                    print("AwaitNodesAgreeOnPrimary: Retrying because " + nodes[i].name +
                          " does not see a primary.");
                    return false;
                }

                if (primary < 0) {
                    // If we haven't seen a primary yet, set it to this.
                    primary = nodesPrimary;
                } else if (primary !== nodesPrimary) {
                    print("AwaitNodesAgreeOnPrimary: Retrying because " + nodes[i].name +
                          " thinks the primary is " + nodes[nodesPrimary].name + " instead of " +
                          nodes[primary].name);
                    return false;
                }
            }

            print("AwaitNodesAgreeOnPrimary: Nodes agreed on primary " + nodes[primary].name);
            return true;
        }, "Awaiting nodes to agree on primary", timeout);
    };

    /**
     * Blocking call, which will wait for a primary to be elected and become master for some
     * pre-defined timeout. If a primary is available it will return a connection to it.
     * Otherwise throws an exception.
     */
    this.getPrimary = function(timeout) {
        timeout = timeout || self.kDefaultTimeoutMS;
        var primary = null;

        assert.soonNoExcept(function() {
            primary = _callIsMaster();
            return primary;
        }, "Finding primary", timeout);

        return primary;
    };

    this.awaitNoPrimary = function(msg, timeout) {
        msg = msg || "Timed out waiting for there to be no primary in replset: " + this.name;
        timeout = timeout || self.kDefaultTimeoutMS;

        assert.soonNoExcept(function() {
            return _callIsMaster() == false;
        }, msg, timeout);
    };

    this.getSecondaries = function(timeout) {
        var master = this.getPrimary(timeout);
        var secs = [];
        for (var i = 0; i < this.nodes.length; i++) {
            if (this.nodes[i] != master) {
                secs.push(this.nodes[i]);
            }
        }

        return secs;
    };

    this.getSecondary = function(timeout) {
        return this.getSecondaries(timeout)[0];
    };

    function isNodeArbiter(node) {
        return node.getDB('admin').isMaster('admin').arbiterOnly;
    }

    this.getArbiters = function() {
        let arbiters = [];
        for (let i = 0; i < this.nodes.length; i++) {
            const node = this.nodes[i];

            let isArbiter = false;

            assert.retryNoExcept(() => {
                isArbiter = isNodeArbiter(node);
                return true;
            }, `Could not call 'isMaster' on ${node}.`, 3, 1000);

            if (isArbiter) {
                arbiters.push(node);
            }
        }
        return arbiters;
    };

    this.getArbiter = function() {
        return this.getArbiters()[0];
    };

    this.status = function(timeout) {
        var master = _callIsMaster();
        if (!master) {
            master = this._liveNodes[0];
        }

        return master.getDB("admin").runCommand({replSetGetStatus: 1});
    };

    /**
     * Adds a node to the replica set managed by this instance.
     */
    this.add = function(config) {
        var nextPort = _allocatePortForNode();
        print("ReplSetTest Next port: " + nextPort);

        this.ports.push(nextPort);
        printjson(this.ports);

        if (_useBridge) {
            _unbridgedPorts.push(_allocatePortForBridge());
        }

        var nextId = this.nodes.length;
        printjson(this.nodes);

        print("ReplSetTest nextId: " + nextId);
        return this.start(nextId, config);
    };

    this.remove = function(nodeId) {
        nodeId = this.getNodeId(nodeId);
        this.nodes.splice(nodeId, 1);
        this.ports.splice(nodeId, 1);

        if (_useBridge) {
            _unbridgedPorts.splice(nodeId, 1);
            _unbridgedNodes.splice(nodeId, 1);
        }
    };

    /*
     * If journaling is disabled or we are using an ephemeral storage engine, set
     * 'writeConcernMajorityJournalDefault' to false for the given 'config' object. If the
     * 'writeConcernMajorityJournalDefault' field is already set, it does not override it,
     * and returns the 'config' object unchanged. Does not affect 'config' when running CSRS.
     */
    this._updateConfigIfNotDurable = function(config) {
        // Get a replica set node (check for use of bridge).
        var replNode = _useBridge ? _unbridgedNodes[0] : this.nodes[0];

        // Don't update replset config for sharding config servers since config servers always
        // require durable storage.
        if (replNode.hasOwnProperty("fullOptions") &&
            replNode.fullOptions.hasOwnProperty("configsvr")) {
            return config;
        }

        // Don't override existing value.
        var wcMajorityJournalField = "writeConcernMajorityJournalDefault";
        if (config.hasOwnProperty(wcMajorityJournalField)) {
            return config;
        }

        // Check journaling by sending commands through the bridge if it's used.
        if (_isRunningWithoutJournaling(this.nodes[0])) {
            config[wcMajorityJournalField] = false;
        }

        return config;
    };

    this._setDefaultConfigOptions = function(config) {
        // Update config for non journaling test variants
        this._updateConfigIfNotDurable(config);
        // Add protocolVersion if missing
        if (!config.hasOwnProperty('protocolVersion')) {
            config['protocolVersion'] = 1;
        }
    };

    function replSetCommandWithRetry(master, cmd) {
        printjson(cmd);
        const cmdName = Object.keys(cmd)[0];
        const errorMsg = `${cmdName} during initiate failed`;
        assert.retry(() => {
            const result = assert.commandWorkedOrFailedWithCode(
                master.runCommand(cmd),
                [
                    ErrorCodes.NodeNotFound,
                    ErrorCodes.NewReplicaSetConfigurationIncompatible,
                    ErrorCodes.InterruptedDueToReplStateChange
                ],
                errorMsg);
            return result.ok;
        }, errorMsg, 3, 5 * 1000);
    }

    /**
     * Runs replSetInitiate on the first node of the replica set.
     * Ensures that a primary is elected (not necessarily node 0).
     * initiate() should be preferred instead of this, but this is useful when the connections
     * aren't authorized to run replSetGetStatus.
     * TODO(SERVER-14017): remove this in favor of using initiate() everywhere.
     */
    this.initiateWithAnyNodeAsPrimary = function(cfg, initCmd, {
        doNotWaitForStableRecoveryTimestamp: doNotWaitForStableRecoveryTimestamp = false
    } = {}) {
        var master = this.nodes[0].getDB("admin");
        var config = cfg || this.getReplSetConfig();
        var cmd = {};
        var cmdKey = initCmd || 'replSetInitiate';

        // Throw an exception if nodes[0] is unelectable in the given config.
        if (!_isElectable(config.members[0])) {
            throw Error("The node at index 0 must be electable");
        }

        // Start up a single node replica set then reconfigure to the correct size (if the config
        // contains more than 1 node), so the primary is elected more quickly.
        var originalMembers, originalSettings;
        if (config.members && config.members.length > 1) {
            originalMembers = config.members.slice();
            config.members = config.members.slice(0, 1);
            originalSettings = config.settings;
            delete config.settings;  // Clear settings to avoid tags referencing sliced nodes.
        }
        this._setDefaultConfigOptions(config);

        cmd[cmdKey] = config;

        // replSetInitiate and replSetReconfig commands can fail with a NodeNotFound error if a
        // heartbeat times out during the quorum check. They may also fail with
        // NewReplicaSetConfigurationIncompatible on similar timeout during the config validation
        // stage while deducing isSelf(). This can fail with an InterruptedDueToReplStateChange
        // error when interrupted. We try several times, to reduce the chance of failing this way.
        replSetCommandWithRetry(master, cmd);
        this.getPrimary();  // Blocks until there is a primary.

        // Initiating a replica set with a single node will use "latest" FCV. This will
        // cause IncompatibleServerVersion errors if additional "last-stable" binary version
        // nodes are subsequently added to the set, since such nodes cannot set their FCV to
        // "latest". Therefore, we make sure the primary is "last-stable" FCV before adding in
        // nodes of different binary versions to the replica set.
        if (jsTest.options().randomBinVersions) {
            assert.commandWorked(
                self.getPrimary().adminCommand({setFeatureCompatibilityVersion: lastStableFCV}));
            checkFCV(self.getPrimary().getDB("admin"), lastStableFCV);
        }

        // Reconfigure the set to contain the correct number of nodes (if necessary).
        if (originalMembers) {
            config.members = originalMembers;
            if (originalSettings) {
                config.settings = originalSettings;
            }
            config.version = 2;

            // Nodes started with the --configsvr flag must have configsvr = true in their config.
            if (this.nodes[0].hasOwnProperty("fullOptions") &&
                this.nodes[0].fullOptions.hasOwnProperty("configsvr")) {
                config.configsvr = true;
            }

            cmd = {replSetReconfig: config};
            print("Reconfiguring replica set to add in other nodes");
            replSetCommandWithRetry(master, cmd);
        }

        // Setup authentication if running test with authentication
        if ((jsTestOptions().keyFile) && cmdKey == 'replSetInitiate') {
            master = this.getPrimary();
            jsTest.authenticateNodes(this.nodes);
        }
        this.awaitSecondaryNodes();
        try {
            this.awaitHighestPriorityNodeIsPrimary();
        } catch (e) {
            // Due to SERVER-14017, the call to awaitHighestPriorityNodeIsPrimary() may fail
            // in certain configurations due to being unauthorized.  In that case we proceed
            // even though we aren't guaranteed that the highest priority node is the one that
            // became primary.
            // TODO(SERVER-14017): Unconditionally expect awaitHighestPriorityNodeIsPrimary to pass.
            assert.eq(ErrorCodes.Unauthorized, e.code, tojson(e));
            print("Running awaitHighestPriorityNodeIsPrimary() during ReplSetTest initialization " +
                  "failed with Unauthorized error, proceeding even though we aren't guaranteed " +
                  "that the highest priority node is primary");
        }

        let shouldWaitForKeys = true;
        if (self.waitForKeys != undefined) {
            shouldWaitForKeys = self.waitForKeys;
            print("Set shouldWaitForKeys from RS options: " + shouldWaitForKeys);
        } else {
            Object.keys(self.nodeOptions).forEach(function(key, index) {
                let val = self.nodeOptions[key];
                if (typeof (val) === "object" &&
                    (val.hasOwnProperty("shardsvr") ||
                     val.hasOwnProperty("binVersion") &&
                         // Should not wait for keys if version is less than 3.6
                         MongoRunner.compareBinVersions(val.binVersion, "3.6") == -1)) {
                    shouldWaitForKeys = false;
                    print("Set shouldWaitForKeys from node options: " + shouldWaitForKeys);
                }
            });
            if (self.startOptions != undefined) {
                let val = self.startOptions;
                if (typeof (val) === "object" &&
                    (val.hasOwnProperty("shardsvr") ||
                     val.hasOwnProperty("binVersion") &&
                         // Should not wait for keys if version is less than 3.6
                         MongoRunner.compareBinVersions(val.binVersion, "3.6") == -1)) {
                    shouldWaitForKeys = false;
                    print("Set shouldWaitForKeys from start options: " + shouldWaitForKeys);
                }
            }
        }
        /**
         * Blocks until the primary node generates cluster time sign keys.
         */
        if (shouldWaitForKeys) {
            var timeout = self.kDefaultTimeoutMS;
            asCluster(this.nodes, function(timeout) {
                print("Waiting for keys to sign $clusterTime to be generated");
                assert.soonNoExcept(function(timeout) {
                    var keyCnt = self.getPrimary(timeout)
                                     .getCollection('admin.system.keys')
                                     .find({purpose: 'HMAC'})
                                     .itcount();
                    return keyCnt >= 2;
                }, "Awaiting keys", timeout);
            });
        }

        // Set 'featureCompatibilityVersion' for the entire replica set, if specified.
        if (jsTest.options().replSetFeatureCompatibilityVersion) {
            // Authenticate before running the command.
            asCluster(self.nodes, function setFCV() {
                let fcv = jsTest.options().replSetFeatureCompatibilityVersion;
                print("Setting feature compatibility version for replica set to '" + fcv + "'");
                assert.commandWorked(
                    self.getPrimary().adminCommand({setFeatureCompatibilityVersion: fcv}));

                // Wait for the new 'featureCompatibilityVersion' to propagate to all nodes in the
                // replica set. The 'setFeatureCompatibilityVersion' command only waits for
                // replication to a majority of nodes by default.
                self.awaitReplication();
            });
        }

        if (!doNotWaitForStableRecoveryTimestamp) {
            self.awaitLastStableRecoveryTimestamp();
        }
    };

    /**
     * Runs replSetInitiate on the replica set and requests the first node to step up as primary.
     * This version should be prefered where possible but requires all connections in the
     * ReplSetTest to be authorized to run replSetGetStatus.
     */
    this.initiateWithNodeZeroAsPrimary = function(cfg, initCmd) {
        this.initiateWithAnyNodeAsPrimary(cfg, initCmd);

        // stepUp() calls awaitReplication() which requires all nodes to be authorized to run
        // replSetGetStatus.
        asCluster(this.nodes, function() {
            self.stepUp(self.nodes[0]);
        });
    };

    /**
     * Runs replSetInitiate on the replica set and requests the first node to step up as
     * primary.
     */
    this.initiate = function(cfg, initCmd) {
        this.initiateWithNodeZeroAsPrimary(cfg, initCmd);
    };

    /**
     * Modifies the election timeout to be 24 hours so that no unplanned elections happen. Then
     * runs replSetInitiate on the replica set with the new config.
     */
    this.initiateWithHighElectionTimeout = function(timeout) {
        let cfg = this.getReplSetConfig();
        cfg.settings = {"electionTimeoutMillis": 24 * 60 * 60 * 1000};
        this.initiate(cfg);
    };

    /**
     * Steps up 'node' as primary.
     * Waits for all nodes to reach the same optime before sending the replSetStepUp command
     * to 'node'.
     * Calls awaitReplication() which requires all connections in 'nodes' to be authenticated.
     */
    this.stepUp = function(node) {
        this.awaitReplication();
        this.awaitNodesAgreeOnAppliedOpTime();
        this.awaitNodesAgreeOnPrimary();
        if (this.getPrimary() === node) {
            return;
        }

        assert.commandWorked(node.adminCommand({replSetStepUp: 1}));
        this.awaitNodesAgreeOnPrimary();
        assert.eq(this.getPrimary(), node, node.host + " was not primary after stepUp");
    };

    /**
     * Gets the current replica set config from the specified node index. If no nodeId is specified,
     * uses the primary node.
     */
    this.getReplSetConfigFromNode = function(nodeId) {
        if (nodeId == undefined) {
            // Use 90 seconds timeout for finding a primary
            return _replSetGetConfig(self.getPrimary(90 * 1000));
        }

        if (!isNumber(nodeId)) {
            throw Error(nodeId + ' is not a number');
        }

        return _replSetGetConfig(self.nodes[nodeId]);
    };

    this.reInitiate = function() {
        var config = this.getReplSetConfigFromNode();
        var newConfig = this.getReplSetConfig();
        // Only reset members.
        config.members = newConfig.members;
        config.version += 1;

        this._setDefaultConfigOptions(config);

        assert.adminCommandWorkedAllowingNetworkError(this.getPrimary(), {replSetReconfig: config});
    };

    /**
     * Blocks until all nodes in the replica set have the same config version as the primary.
     **/
    this.awaitNodesAgreeOnConfigVersion = function(timeout) {
        timeout = timeout || this.kDefaultTimeoutMS;

        assert.soonNoExcept(function() {
            var primaryVersion = self.getPrimary().adminCommand({ismaster: 1}).setVersion;

            for (var i = 0; i < self.nodes.length; i++) {
                var version = self.nodes[i].adminCommand({ismaster: 1}).setVersion;
                assert.eq(version,
                          primaryVersion,
                          "waiting for secondary node " + self.nodes[i].host +
                              " with config version of " + version +
                              " to match the version of the primary " + primaryVersion);
            }

            return true;
        }, "Awaiting nodes to agree on config version", timeout);
    };

    /**
     * Waits for the last oplog entry on the primary to be visible in the committed snapshot view
     * of the oplog on *all* secondaries. When majority read concern is disabled, there is no
     * committed snapshot view, so this function waits for the knowledge of the majority commit
     * point on each node to advance to the optime of the last oplog entry on the primary.
     * Returns last oplog entry.
     */
    this.awaitLastOpCommitted = function(timeout, members) {
        var rst = this;
        var master = rst.getPrimary();
        var masterOpTime = _getLastOpTime(master);

        let membersToCheck;
        if (members !== undefined) {
            print("Waiting for op with OpTime " + tojson(masterOpTime) + " to be committed on " +
                  members.map(s => s.host));

            membersToCheck = members;
        } else {
            print("Waiting for op with OpTime " + tojson(masterOpTime) +
                  " to be committed on all secondaries");

            membersToCheck = rst.nodes;
        }

        assert.soonNoExcept(
            function() {
                for (var i = 0; i < membersToCheck.length; i++) {
                    var node = membersToCheck[i];

                    // Continue if we're connected to an arbiter
                    var res = assert.commandWorked(node.adminCommand({replSetGetStatus: 1}));
                    if (res.myState == ReplSetTest.State.ARBITER) {
                        continue;
                    }
                    var rcmOpTime = _getReadConcernMajorityOpTime(node);
                    if (friendlyEqual(rcmOpTime, {ts: Timestamp(0, 0), t: NumberLong(0)})) {
                        return false;
                    }
                    if (rs.compareOpTimes(rcmOpTime, masterOpTime) < 0) {
                        return false;
                    }
                }

                return true;
            },
            "Op with OpTime " + tojson(masterOpTime) + " failed to be committed on all secondaries",
            timeout);

        return masterOpTime;
    };

    /**
     * This function performs some writes and then waits for all nodes in this replica set to
     * establish a stable recovery timestamp. The writes are necessary to prompt storage engines to
     * quickly establish stable recovery timestamps.
     *
     * A stable recovery timestamp ensures recoverable rollback is possible, as well as startup
     * recovery without re-initial syncing in the case of durable storage engines. By waiting for
     * all nodes to report having a stable recovery timestamp, we ensure a degree of stability in
     * our tests to run as expected.
     */
    this.awaitLastStableRecoveryTimestamp = function() {
        let rst = this;
        let master = rst.getPrimary();
        let id = tojson(rst.nodeList());

        // All nodes must be in primary/secondary state prior to this point. Perform a majority
        // write to ensure there is a committed operation on the set. The commit point will
        // propagate to all members and trigger a stable checkpoint on all persisted storage engines
        // nodes.
        function advanceCommitPoint(master) {
            // Shadow 'db' so that we can call 'advanceCommitPoint' directly on the primary node.
            let db = master.getDB('admin');
            const appendOplogNoteFn = function() {
                assert.commandWorked(db.adminCommand({
                    "appendOplogNote": 1,
                    "data": {"awaitLastStableRecoveryTimestamp": 1},
                    "writeConcern": {"w": "majority", "wtimeout": ReplSetTest.kDefaultTimeoutMS}
                }));
            };

            // TODO(SERVER-14017): Remove this extra sub-shell in favor of a cleaner authentication
            // solution.
            const masterId = "n" + rst.getNodeId(master);
            const masterOptions = rst.nodeOptions[masterId] || {};
            if (masterOptions.clusterAuthMode === "x509") {
                print("AwaitLastStableRecoveryTimestamp: authenticating on separate shell " +
                      "with x509 for " + id);
                const subShellArgs = [
                    'mongo',
                    '--ssl',
                    '--sslCAFile=' + masterOptions.sslCAFile,
                    '--sslPEMKeyFile=' + masterOptions.sslPEMKeyFile,
                    '--sslAllowInvalidHostnames',
                    '--authenticationDatabase=$external',
                    '--authenticationMechanism=MONGODB-X509',
                    master.host,
                    '--eval',
                    `(${appendOplogNoteFn.toString()})();`
                ];

                const retVal = _runMongoProgram(...subShellArgs);
                assert.eq(retVal, 0, 'mongo shell did not succeed with exit code 0');
            } else {
                if (masterOptions.clusterAuthMode) {
                    print("AwaitLastStableRecoveryTimestamp: authenticating with " +
                          masterOptions.clusterAuthMode + " for " + id);
                }
                asCluster(master, appendOplogNoteFn, masterOptions.keyFile);
            }
        }

        print("AwaitLastStableRecoveryTimestamp: Beginning for " + id);

        let replSetStatus = assert.commandWorked(master.adminCommand("replSetGetStatus"));
        if (replSetStatus["configsvr"]) {
            // Performing dummy replicated writes against a configsvr is hard, especially if auth
            // is also enabled.
            return;
        }

        rst.awaitNodesAgreeOnPrimary();
        master = rst.getPrimary();

        print("AwaitLastStableRecoveryTimestamp: ensuring the commit point advances for " + id);
        advanceCommitPoint(master);

        print("AwaitLastStableRecoveryTimestamp: Waiting for stable recovery timestamps for " + id);

        assert.soonNoExcept(function() {
            for (let node of rst.nodes) {
                // The `lastStableRecoveryTimestamp` field contains a stable timestamp guaranteed to
                // exist on storage engine recovery to stable timestamp.
                let res = assert.commandWorked(node.adminCommand({replSetGetStatus: 1}));

                // Continue if we're connected to an arbiter.
                if (res.myState === ReplSetTest.State.ARBITER) {
                    continue;
                }

                // A missing `lastStableRecoveryTimestamp` field indicates that the storage
                // engine does not support `recover to a stable timestamp`.
                //
                // A null `lastStableRecoveryTimestamp` indicates that the storage engine supports
                // "recover to a stable timestamp", but does not have a stable recovery timestamp
                // yet.
                if (res.hasOwnProperty("lastStableRecoveryTimestamp") &&
                    res.lastStableRecoveryTimestamp.getTime() === 0) {
                    print("AwaitLastStableRecoveryTimestamp: " + node.host +
                          " does not have a stable recovery timestamp yet.");
                    return false;
                }
            }

            return true;
        }, "Not all members have a stable recovery timestamp");

        print("AwaitLastStableRecoveryTimestamp: A stable recovery timestamp has successfully " +
              "established on " + id);
    };

    // Wait until the optime of the specified type reaches the primary's last applied optime. Blocks
    // on all secondary nodes or just 'slaves', if specified. The timeout will reset if any of the
    // secondaries makes progress.
    this.awaitReplication = function(timeout, secondaryOpTimeType, slaves) {
        if (slaves !== undefined && slaves !== self._slaves) {
            print("ReplSetTest awaitReplication: going to check only " + slaves.map(s => s.host));
        }

        timeout = timeout || self.kDefaultTimeoutMS;

        secondaryOpTimeType = secondaryOpTimeType || ReplSetTest.OpTimeType.LAST_APPLIED;

        var masterLatestOpTime;

        // Blocking call, which will wait for the last optime written on the master to be available
        var awaitLastOpTimeWrittenFn = function() {
            var master = self.getPrimary();
            assert.soonNoExcept(function() {
                try {
                    masterLatestOpTime = _getLastOpTime(master);
                } catch (e) {
                    print("ReplSetTest caught exception " + e);
                    return false;
                }

                return true;
            }, "awaiting oplog query", timeout);
        };

        awaitLastOpTimeWrittenFn();

        // get the latest config version from master (with a few retries in case of error)
        var masterConfigVersion;
        var masterName;
        var master;
        var num_attempts = 3;

        assert.retryNoExcept(() => {
            master = this.getPrimary();
            masterConfigVersion = this.getReplSetConfigFromNode().version;
            masterName = master.host;
            return true;
        }, "ReplSetTest awaitReplication: couldnt get repl set config.", num_attempts, 1000);

        print("ReplSetTest awaitReplication: starting: optime for primary, " + masterName +
              ", is " + tojson(masterLatestOpTime));

        let nodesCaughtUp = false;
        let slavesToCheck = slaves || self._slaves;
        let nodeProgress = Array(slavesToCheck.length);

        const Progress = Object.freeze({
            Skip: 'Skip',
            CaughtUp: 'CaughtUp',
            InProgress: 'InProgress',
            Stuck: 'Stuck',
            ConfigMismatch: 'ConfigMismatch'
        });

        function checkProgressSingleNode(index, secondaryCount) {
            var slave = slavesToCheck[index];
            var slaveName = slave.host;

            var slaveConfigVersion = slave.getDB("local")['system.replset'].findOne().version;

            if (masterConfigVersion != slaveConfigVersion) {
                print("ReplSetTest awaitReplication: secondary #" + secondaryCount + ", " +
                      slaveName + ", has config version #" + slaveConfigVersion +
                      ", but expected config version #" + masterConfigVersion);

                if (slaveConfigVersion > masterConfigVersion) {
                    master = self.getPrimary();
                    masterConfigVersion = master.getDB("local")['system.replset'].findOne().version;
                    masterName = master.host;

                    print("ReplSetTest awaitReplication: optime for primary, " + masterName +
                          ", is " + tojson(masterLatestOpTime));
                }

                return Progress.ConfigMismatch;
            }

            // Skip this node if we're connected to an arbiter
            var res = assert.commandWorked(slave.adminCommand({replSetGetStatus: 1}));
            if (res.myState == ReplSetTest.State.ARBITER) {
                return Progress.Skip;
            }

            print("ReplSetTest awaitReplication: checking secondary #" + secondaryCount + ": " +
                  slaveName);

            slave.getDB("admin").getMongo().setSlaveOk();

            var slaveOpTime;
            if (secondaryOpTimeType == ReplSetTest.OpTimeType.LAST_DURABLE) {
                slaveOpTime = _getDurableOpTime(slave);
            } else {
                slaveOpTime = _getLastOpTime(slave);
            }

            // If the node doesn't have a valid opTime, it likely hasn't received any writes from
            // the primary yet.
            if (!rs.isValidOpTime(slaveOpTime)) {
                print("ReplSetTest awaitReplication: optime for secondary #" + secondaryCount +
                      ", " + slaveName + ", is " + tojson(slaveOpTime) + ", which is NOT valid.");
                return Progress.Stuck;
            }

            // See if the node made progress. We count it as progress even if the node's last optime
            // went backwards because that means the node is in rollback.
            let madeProgress =
                (nodeProgress[index] && (rs.compareOpTimes(nodeProgress[index], slaveOpTime) != 0));
            nodeProgress[index] = slaveOpTime;

            if (rs.compareOpTimes(masterLatestOpTime, slaveOpTime) < 0) {
                masterLatestOpTime = _getLastOpTime(master);
                print("ReplSetTest awaitReplication: optime for " + slaveName +
                      " is newer, resetting latest primary optime to " +
                      tojson(masterLatestOpTime) + ". Also resetting awaitReplication timeout");
                return Progress.InProgress;
            }

            if (!friendlyEqual(masterLatestOpTime, slaveOpTime)) {
                print("ReplSetTest awaitReplication: optime for secondary #" + secondaryCount +
                      ", " + slaveName + ", is " + tojson(slaveOpTime) + " but latest is " +
                      tojson(masterLatestOpTime));
                print("ReplSetTest awaitReplication: secondary #" + secondaryCount + ", " +
                      slaveName + ", is NOT synced");

                // Reset the timeout if a node makes progress, but isn't caught up yet.
                if (madeProgress) {
                    print("ReplSetTest awaitReplication: secondary #" + secondaryCount + ", " +
                          slaveName + ", has made progress. Resetting awaitReplication timeout");
                    return Progress.InProgress;
                }
                return Progress.Stuck;
            }

            print("ReplSetTest awaitReplication: secondary #" + secondaryCount + ", " + slaveName +
                  ", is synced");
            return Progress.CaughtUp;
        }

        // We will reset the timeout if a nodes makes progress, but still isn't caught up yet.
        while (!nodesCaughtUp) {
            assert.soonNoExcept(function() {
                try {
                    print("ReplSetTest awaitReplication: checking secondaries against latest " +
                          "primary optime " + tojson(masterLatestOpTime));
                    var secondaryCount = 0;

                    for (var i = 0; i < slavesToCheck.length; i++) {
                        const action = checkProgressSingleNode(i, secondaryCount);

                        switch (action) {
                            case Progress.CaughtUp:
                                // We only need to increment the secondaryCount if this node is
                                // caught up.
                                secondaryCount++;
                                continue;
                            case Progress.Skip:
                                // Don't increment secondaryCount because this node is an arbiter.
                                continue;
                            case Progress.InProgress:
                                return true;
                            case Progress.Stuck:
                            case Progress.ConfigMismatch:
                                return false;
                            default:
                                throw Error("invalid action: " + tojson(action));
                        }
                    }

                    print("ReplSetTest awaitReplication: finished: all " + secondaryCount +
                          " secondaries synced at optime " + tojson(masterLatestOpTime));
                    nodesCaughtUp = true;
                    return true;
                } catch (e) {
                    print("ReplSetTest awaitReplication: caught exception " + e);

                    // We might have a new master now
                    awaitLastOpTimeWrittenFn();

                    print("ReplSetTest awaitReplication: resetting: optime for primary " +
                          self._master + " is " + tojson(masterLatestOpTime));

                    return false;
                }
            }, "awaiting replication", timeout);
        }
    };

    // TODO: SERVER-38961 Remove when simultaneous index builds complete.
    this.waitForAllIndexBuildsToFinish = function(dbName, collName) {
        // Run a no-op command and wait for it to be applied on secondaries. Due to the asynchronous
        // completion nature of indexes on secondaries, we can guarantee an index build is complete
        // on all secondaries once all secondaries have applied this collMod command.
        assert.commandWorked(this.getPrimary().getDB(dbName).runCommand({collMod: collName}));
        this.awaitReplication();
    };

    this.getHashesUsingSessions = function(sessions, dbName, {
        filterCapped: filterCapped = true,
        filterMapReduce: filterMapReduce = true,
        readAtClusterTime,
    } = {}) {
        return sessions.map(session => {
            const commandObj = {dbHash: 1};
            if (readAtClusterTime !== undefined) {
                commandObj.$_internalReadAtClusterTime = readAtClusterTime;
            }

            const db = session.getDatabase(dbName);
            const res = assert.commandWorked(db.runCommand(commandObj));

            // The "capped" field in the dbHash command response is new as of MongoDB 4.0.
            const cappedCollections = new Set(filterCapped ? res.capped : []);

            for (let collName of Object.keys(res.collections)) {
                // Capped collections are not necessarily truncated at the same points across
                // replica set members and may therefore not have the same md5sum. We remove them
                // from the dbHash command response to avoid an already known case of a mismatch.
                // See SERVER-16049 for more details.
                //
                // If a map-reduce operation is interrupted by the server stepping down, then an
                // unreplicated "tmp.mr." collection may be left behind. We remove it from the
                // dbHash command response to avoid an already known case of a mismatch.
                // TODO SERVER-27147: Stop filtering out "tmp.mr." collections.
                if (cappedCollections.has(collName) ||
                    (filterMapReduce && collName.startsWith("tmp.mr."))) {
                    delete res.collections[collName];
                    // The "uuids" field in the dbHash command response is new as of MongoDB 4.0.
                    if (res.hasOwnProperty("uuids")) {
                        delete res.uuids[collName];
                    }
                }
            }

            return res;
        });
    };

    this.getCollectionDiffUsingSessions = function(
        primarySession, secondarySession, dbName, collNameOrUUID, readAtClusterTime) {
        function PeekableCursor(cursor) {
            let _stashedDoc;

            this.hasNext = function hasNext() {
                return cursor.hasNext();
            };

            this.peekNext = function peekNext() {
                if (_stashedDoc === undefined) {
                    _stashedDoc = cursor.next();
                }
                return _stashedDoc;
            };

            this.next = function next() {
                const result = (_stashedDoc === undefined) ? cursor.next() : _stashedDoc;
                _stashedDoc = undefined;
                return result;
            };
        }

        const docsWithDifferentContents = [];
        const docsMissingOnPrimary = [];
        const docsMissingOnSecondary = [];

        const primaryDB = primarySession.getDatabase(dbName);
        const secondaryDB = secondarySession.getDatabase(dbName);

        const commandObj = {find: collNameOrUUID, sort: {_id: 1}};
        if (readAtClusterTime !== undefined) {
            commandObj.$_internalReadAtClusterTime = readAtClusterTime;
        }

        const primaryCursor =
            new PeekableCursor(new DBCommandCursor(primaryDB, primaryDB.runCommand(commandObj)));

        const secondaryCursor = new PeekableCursor(
            new DBCommandCursor(secondaryDB, secondaryDB.runCommand(commandObj)));

        while (primaryCursor.hasNext() && secondaryCursor.hasNext()) {
            const primaryDoc = primaryCursor.peekNext();
            const secondaryDoc = secondaryCursor.peekNext();

            if (bsonBinaryEqual(primaryDoc, secondaryDoc)) {
                // The same document was found on the primary and secondary so we just move on to
                // the next document for both cursors.
                primaryCursor.next();
                secondaryCursor.next();
                continue;
            }

            const ordering = bsonWoCompare({_: primaryDoc._id}, {_: secondaryDoc._id});
            if (ordering === 0) {
                // The documents have the same _id but have different contents.
                docsWithDifferentContents.push({primary: primaryDoc, secondary: secondaryDoc});
                primaryCursor.next();
                secondaryCursor.next();
            } else if (ordering < 0) {
                // The primary's next document has a smaller _id than the secondary's next document.
                // Since we are iterating the documents in ascending order by their _id, we'll never
                // see a document with 'primaryDoc._id' on the secondary.
                docsMissingOnSecondary.push(primaryDoc);
                primaryCursor.next();
            } else if (ordering > 0) {
                // The primary's next document has a larger _id than the secondary's next document.
                // Since we are iterating the documents in ascending order by their _id, we'll never
                // see a document with 'secondaryDoc._id' on the primary.
                docsMissingOnPrimary.push(secondaryDoc);
                secondaryCursor.next();
            }
        }

        while (primaryCursor.hasNext()) {
            // We've exhausted the secondary's cursor already, so everything remaining from the
            // primary's cursor must be missing from secondary.
            docsMissingOnSecondary.push(primaryCursor.next());
        }

        while (secondaryCursor.hasNext()) {
            // We've exhausted the primary's cursor already, so everything remaining from the
            // secondary's cursor must be missing from primary.
            docsMissingOnPrimary.push(secondaryCursor.next());
        }

        return {docsWithDifferentContents, docsMissingOnPrimary, docsMissingOnSecondary};
    };

    // Gets the dbhash for the current primary and for all secondaries (or the members of 'slaves',
    // if specified).
    this.getHashes = function(dbName, slaves) {
        assert.neq(dbName, 'local', 'Cannot run getHashes() on the "local" database');

        // getPrimary() repopulates 'self._slaves'.
        this.getPrimary();
        slaves = slaves || this._slaves;

        const sessions = [
            this._master,
            ...slaves.filter(conn => {
                return !conn.adminCommand({isMaster: 1}).arbiterOnly;
            })
        ].map(conn => conn.getDB('test').getSession());

        // getHashes() is sometimes called for versions of MongoDB earlier than 4.0 so we cannot use
        // the dbHash command directly to filter out capped collections. checkReplicatedDataHashes()
        // uses the listCollections command after awaiting replication to determine if a collection
        // is capped.
        const hashes = this.getHashesUsingSessions(sessions, dbName, {filterCapped: false});
        return {master: hashes[0], slaves: hashes.slice(1)};
    };

    this.findOplog = function(conn, query, limit) {
        return conn.getDB('local')
            .getCollection(oplogName)
            .find(query)
            .sort({$natural: -1})
            .limit(limit);
    };

    this.dumpOplog = function(conn, query = {}, limit = 10) {
        var log = 'Dumping the latest ' + limit + ' documents that match ' + tojson(query) +
            ' from the oplog ' + oplogName + ' of ' + conn.host;
        let entries = [];
        let cursor = this.findOplog(conn, query, limit);
        cursor.forEach(function(entry) {
            log = log + '\n' + tojsononeline(entry);
            entries.push(entry);
        });
        jsTestLog(log);
        return entries;
    };

    // Call the provided checkerFunction, after the replica set has been write locked.
    this.checkReplicaSet = function(checkerFunction, slaves, ...checkerFunctionArgs) {
        assert.eq(typeof checkerFunction,
                  "function",
                  "Expected checkerFunction parameter to be a function");

        // Call getPrimary to populate rst with information about the nodes.
        var primary = this.getPrimary();
        assert(primary, 'calling getPrimary() failed');
        slaves = slaves || self._slaves;

        // Since we cannot determine if there is a background index in progress (SERVER-26624), we
        // use the "collMod" command to wait for any index builds that may be in progress on the
        // primary or on one of the secondaries to complete.
        for (let dbName of primary.getDBNames()) {
            if (dbName === "local") {
                continue;
            }

            let dbHandle = primary.getDB(dbName);
            dbHandle.getCollectionInfos({$or: [{type: "collection"}, {type: {$exists: false}}]})
                .forEach(function(collInfo) {
                    // Skip system collections. We handle here rather than in the getCollectionInfos
                    // filter to take advantage of the fact that a simple 'collection' filter will
                    // skip view evaluation, and therefore won't fail on an invalid view.
                    if (!collInfo.name.startsWith('system.')) {
                        // We intentionally await replication without doing any I/O to avoid any
                        // overhead. We call awaitReplication() later on to ensure the collMod
                        // is replicated to all nodes.
                        try {
                            assert.commandWorked(dbHandle.runCommand({collMod: collInfo.name}));
                        } catch (e) {
                            // Ignore NamespaceNotFound errors because a background thread could
                            // have dropped the collection after getCollectionInfos but before
                            // running collMod.
                            if (e.code != ErrorCodes.NamespaceNotFound) {
                                throw e;
                            }
                        }
                    }
                });
        }

        var activeException = false;

        // Lock the primary to prevent the TTL monitor from deleting expired documents in
        // the background while we are getting the dbhashes of the replica set members. It's not
        // important if the storage engine fails to perform its fsync operation. The only
        // requirement is that writes are locked out.
        assert.commandWorked(primary.adminCommand({fsync: 1, lock: 1, allowFsyncFailure: true}),
                             'failed to lock the primary');
        try {
            this.awaitReplication(null, null, slaves);
            checkerFunction.apply(this, checkerFunctionArgs);
        } catch (e) {
            activeException = true;
            throw e;
        } finally {
            // Allow writes on the primary.
            var res = primary.adminCommand({fsyncUnlock: 1});

            if (!res.ok) {
                var msg = 'failed to unlock the primary, which may cause this' +
                    ' test to hang: ' + tojson(res);
                if (activeException) {
                    print(msg);
                } else {
                    throw new Error(msg);
                }
            }
        }
    };

    // Check the replicated data hashes for all live nodes in the set.
    this.checkReplicatedDataHashes = function(
        msgPrefix = 'checkReplicatedDataHashes', excludedDBs = [], ignoreUUIDs = false) {
        // Return items that are in either Array `a` or `b` but not both. Note that this will
        // not work with arrays containing NaN. Array.indexOf(NaN) will always return -1.

        var collectionPrinted = new Set();

        function arraySymmetricDifference(a, b) {
            var inAOnly = a.filter(function(elem) {
                return b.indexOf(elem) < 0;
            });

            var inBOnly = b.filter(function(elem) {
                return a.indexOf(elem) < 0;
            });

            return inAOnly.concat(inBOnly);
        }

        function checkDBHashesForReplSet(rst, dbBlacklist = [], slaves, msgPrefix, ignoreUUIDs) {
            // We don't expect the local database to match because some of its
            // collections are not replicated.
            dbBlacklist.push('local');
            slaves = slaves || rst._slaves;

            var success = true;
            var hasDumpedOplog = false;

            // Use '_master' instead of getPrimary() to avoid the detection of a new primary.
            // '_master' must have been populated.
            var primary = rst._master;
            var combinedDBs = new Set(primary.getDBNames());
            const replSetConfig = rst.getReplSetConfigFromNode();

            print("checkDBHashesForReplSet checking data hashes against primary: " + primary.host);

            slaves.forEach(secondary => {
                print("checkDBHashesForReplSet going to check data hashes on secondary: " +
                      secondary.host);
                secondary.getDBNames().forEach(dbName => combinedDBs.add(dbName));
            });

            for (var dbName of combinedDBs) {
                if (Array.contains(dbBlacklist, dbName)) {
                    continue;
                }

                const dbHashes = rst.getHashes(dbName, slaves);
                const primaryDBHash = dbHashes.master;
                const primaryCollections = Object.keys(primaryDBHash.collections);
                assert.commandWorked(primaryDBHash);

                // Filter only collections that were retrieved by the dbhash. listCollections
                // may include non-replicated collections like system.profile.
                const primaryCollInfos = new CollInfos(primary, 'primary', dbName);
                primaryCollInfos.filter(primaryCollections);

                dbHashes.slaves.forEach(secondaryDBHash => {
                    assert.commandWorked(secondaryDBHash);

                    var secondary = secondaryDBHash._mongo;
                    var secondaryCollections = Object.keys(secondaryDBHash.collections);
                    // Check that collection information is consistent on the primary and
                    // secondaries.
                    const secondaryCollInfos = new CollInfos(secondary, 'secondary', dbName);
                    secondaryCollInfos.filter(secondaryCollections);

                    if (primaryCollections.length !== secondaryCollections.length) {
                        print(
                            msgPrefix +
                            ', the primary and secondary have a different number of collections: ' +
                            tojson(dbHashes));
                        for (var diffColl of arraySymmetricDifference(primaryCollections,
                                                                      secondaryCollections)) {
                            DataConsistencyChecker.dumpCollectionDiff(this,
                                                                      collectionPrinted,
                                                                      primaryCollInfos,
                                                                      secondaryCollInfos,
                                                                      diffColl);
                        }
                        success = false;
                    }

                    const nonCappedCollNames = primaryCollInfos.getNonCappedCollNames();
                    // Only compare the dbhashes of non-capped collections because capped
                    // collections are not necessarily truncated at the same points
                    // across replica set members.
                    nonCappedCollNames.forEach(collName => {
                        if (primaryDBHash.collections[collName] !==
                            secondaryDBHash.collections[collName]) {
                            print(msgPrefix +
                                  ', the primary and secondary have a different hash for the' +
                                  ' collection ' + dbName + '.' + collName + ': ' +
                                  tojson(dbHashes));
                            DataConsistencyChecker.dumpCollectionDiff(this,
                                                                      collectionPrinted,
                                                                      primaryCollInfos,
                                                                      secondaryCollInfos,
                                                                      collName);
                            success = false;
                        }
                    });

                    secondaryCollInfos.collInfosRes.forEach(secondaryInfo => {
                        primaryCollInfos.collInfosRes.forEach(primaryInfo => {
                            if (secondaryInfo.name === primaryInfo.name &&
                                secondaryInfo.type === primaryInfo.type) {
                                if (ignoreUUIDs) {
                                    print(msgPrefix + ", skipping UUID check for " +
                                          primaryInfo.name);
                                    primaryInfo.info.uuid = null;
                                    secondaryInfo.info.uuid = null;
                                }

                                // Ignore the 'flags' collection option as it was removed in 4.2
                                primaryInfo.options.flags = null;
                                secondaryInfo.options.flags = null;

                                // Ignore the 'ns' field in the 'idIndex' field as 'ns' was removed
                                // from index specs in 4.4.
                                if (primaryInfo.idIndex) {
                                    primaryInfo.idIndex.ns = null;
                                    secondaryInfo.idIndex.ns = null;
                                }

                                if (!bsonBinaryEqual(secondaryInfo, primaryInfo)) {
                                    print(msgPrefix +
                                          ', the primary and secondary have different ' +
                                          'attributes for the collection or view ' + dbName + '.' +
                                          secondaryInfo.name);
                                    DataConsistencyChecker.dumpCollectionDiff(this,
                                                                              collectionPrinted,
                                                                              primaryCollInfos,
                                                                              secondaryCollInfos,
                                                                              secondaryInfo.name);
                                    success = false;
                                }
                            }
                        });
                    });

                    // Check that the following collection stats are the same across replica set
                    // members:
                    //  capped
                    //  nindexes, except on nodes with buildIndexes: false
                    //  ns
                    const hasSecondaryIndexes =
                        replSetConfig.members[rst.getNodeId(secondary)].buildIndexes !== false;
                    primaryCollections.forEach(collName => {
                        var primaryCollStats =
                            primary.getDB(dbName).runCommand({collStats: collName});
                        var secondaryCollStats =
                            secondary.getDB(dbName).runCommand({collStats: collName});

                        if (primaryCollStats.ok !== 1 || secondaryCollStats.ok !== 1) {
                            primaryCollInfos.print(collectionPrinted, collName);
                            secondaryCollInfos.print(collectionPrinted, collName);
                            success = false;
                        } else if (primaryCollStats.capped !== secondaryCollStats.capped ||
                                   (hasSecondaryIndexes &&
                                    primaryCollStats.nindexes !== secondaryCollStats.nindexes) ||
                                   primaryCollStats.ns !== secondaryCollStats.ns) {
                            print(msgPrefix +
                                  ', the primary and secondary have different stats for the ' +
                                  'collection ' + dbName + '.' + collName);
                            DataConsistencyChecker.dumpCollectionDiff(this,
                                                                      collectionPrinted,
                                                                      primaryCollInfos,
                                                                      secondaryCollInfos,
                                                                      collName);
                            success = false;
                        }
                    });

                    if (nonCappedCollNames.length === primaryCollections.length) {
                        // If the primary and secondary have the same hashes for all the
                        // collections in the database and there aren't any capped collections,
                        // then the hashes for the whole database should match.
                        if (primaryDBHash.md5 !== secondaryDBHash.md5) {
                            print(msgPrefix +
                                  ', the primary and secondary have a different hash for ' +
                                  'the ' + dbName + ' database: ' + tojson(dbHashes));
                            success = false;
                        }
                    }

                    if (!success) {
                        if (!hasDumpedOplog) {
                            print("checkDBHashesForReplSet dumping oplogs from all nodes");
                            this.dumpOplog(primary, {}, 100);
                            rst.getSecondaries().forEach(secondary =>
                                                             this.dumpOplog(secondary, {}, 100));
                            hasDumpedOplog = true;
                        }
                    }
                });
            }

            assert(success, 'dbhash mismatch between primary and secondary');
        }

        var liveSlaves = _determineLiveSlaves();
        this.checkReplicaSet(checkDBHashesForReplSet,
                             liveSlaves,
                             this,
                             excludedDBs,
                             liveSlaves,
                             msgPrefix,
                             ignoreUUIDs);
    };

    this.checkOplogs = function(msgPrefix) {
        var liveSlaves = _determineLiveSlaves();
        this.checkReplicaSet(checkOplogs, liveSlaves, this, liveSlaves, msgPrefix);
    };

    /**
     * Check oplogs on all nodes, by reading from the last time. Since the oplog is a capped
     * collection, each node may not contain the same number of entries and stop if the cursor
     * is exhausted on any node being checked.
     */
    function checkOplogs(rst, slaves, msgPrefix = 'checkOplogs') {
        slaves = slaves || rst._slaves;
        const kCappedPositionLostSentinel = Object.create(null);
        const OplogReader = function(mongo) {
            this._safelyPerformCursorOperation = function(name, operation, onCappedPositionLost) {
                if (!this.cursor) {
                    throw new Error("OplogReader is not open!");
                }

                if (this._cursorExhausted) {
                    return onCappedPositionLost;
                }

                try {
                    return operation(this.cursor);
                } catch (err) {
                    print("Error: " + name + " threw '" + err.message + "' on " + this.mongo.host);
                    // Occasionally, the capped collection will get truncated while we are iterating
                    // over it. Since we are iterating over the collection in reverse, getting a
                    // truncated item means we've reached the end of the list, so return false.
                    if (err.code === ErrorCodes.CappedPositionLost) {
                        this.cursor.close();
                        this._cursorExhausted = true;
                        return onCappedPositionLost;
                    }

                    throw err;
                }
            };

            this.next = function() {
                this._safelyPerformCursorOperation('next', function(cursor) {
                    return cursor.next();
                }, kCappedPositionLostSentinel);
            };

            this.hasNext = function() {
                this._safelyPerformCursorOperation('hasNext', function(cursor) {
                    return cursor.hasNext();
                }, false);
            };

            this.query = function(ts) {
                const coll = this.getOplogColl();
                const query = {ts: {$gte: ts ? ts : new Timestamp()}};
                // Set the cursor to read backwards, from last to first. We also set the cursor not
                // to time out since it may take a while to process each batch and a test may have
                // changed "cursorTimeoutMillis" to a short time period.
                this._cursorExhausted = false;
                this.cursor = coll.find(query).sort({$natural: -1}).noCursorTimeout();
            };

            this.getFirstDoc = function() {
                return this.getOplogColl().find().sort({$natural: 1}).limit(-1).next();
            };

            this.getOplogColl = function() {
                return this.mongo.getDB("local")[oplogName];
            };

            this.cursor = null;
            this._cursorExhausted = true;
            this.mongo = mongo;
        };

        function assertOplogEntriesEq(oplogEntry0, oplogEntry1, reader0, reader1, prevOplogEntry) {
            if (!bsonBinaryEqual(oplogEntry0, oplogEntry1)) {
                const query = prevOplogEntry ? {ts: {$lte: prevOplogEntry.ts}} : {};
                rst.nodes.forEach(node => this.dumpOplog(node, query, 100));
                const log = msgPrefix + ", non-matching oplog entries for the following nodes: \n" +
                    reader0.mongo.host + ": " + tojsononeline(oplogEntry0) + "\n" +
                    reader1.mongo.host + ": " + tojsononeline(oplogEntry1);
                assert(false, log);
            }
        }

        print("checkOplogs starting oplog checks.");
        if (slaves.length >= 1) {
            let readers = [];
            let smallestTS = new Timestamp(Math.pow(2, 32) - 1, Math.pow(2, 32) - 1);
            const nodes = rst.nodes;
            let firstReaderIndex;
            for (let i = 0; i < nodes.length; i++) {
                const node = nodes[i];

                if (rst._master !== node && !slaves.includes(node)) {
                    print("checkOplogs skipping oplog of node: " + node.host);
                    continue;
                }

                // Arbiters have no documents in the oplog.
                if (isNodeArbiter(node)) {
                    jsTestLog("checkOplogs skipping oplog of arbiter: " + node.host);
                    continue;
                }

                print("checkOplogs going to check oplog of node: " + node.host);
                readers[i] = new OplogReader(node);
                const currTS = readers[i].getFirstDoc().ts;
                // Find the reader which has the smallestTS. This reader should have the most
                // number of documents in the oplog.
                if (timestampCmp(currTS, smallestTS) < 0) {
                    smallestTS = currTS;
                    firstReaderIndex = i;
                }
                // Start all oplogReaders at their last document.
                readers[i].query();
            }

            // Read from the reader which has the most oplog entries.
            // Note, we read the oplog backwards from last to first.
            const firstReader = readers[firstReaderIndex];
            let prevOplogEntry;
            while (firstReader.hasNext()) {
                const oplogEntry = firstReader.next();
                if (oplogEntry === kCappedPositionLostSentinel) {
                    // When using legacy OP_QUERY/OP_GET_MORE reads against mongos, it is
                    // possible for hasNext() to return true but for next() to throw an exception.
                    break;
                }

                for (let i = 0; i < nodes.length; i++) {
                    // Skip reading from this reader if the index is the same as firstReader or
                    // the cursor is exhausted.
                    if (i === firstReaderIndex || !(readers[i] && readers[i].hasNext())) {
                        continue;
                    }

                    const otherOplogEntry = readers[i].next();
                    if (otherOplogEntry && otherOplogEntry !== kCappedPositionLostSentinel) {
                        assertOplogEntriesEq(
                            oplogEntry, otherOplogEntry, firstReader, readers[i], prevOplogEntry);
                    }
                }
                prevOplogEntry = oplogEntry;
            }
        }
        print("checkOplogs oplog checks complete.");
    }

    /**
     * Checks that 'fastCount' matches an iterative count for all collections.
     */
    this.checkCollectionCounts = function(msgPrefix = 'checkCollectionCounts') {
        let success = true;
        const errPrefix = `${msgPrefix}, counts did not match for collection`;

        function checkCollectionCount(coll) {
            const itCount = coll.find().itcount();
            const fastCount = coll.count();
            if (itCount !== fastCount) {
                print(`${errPrefix} ${coll.getFullName()} on ${coll.getMongo().host}.` +
                      ` itcount: ${itCount}, fast count: ${fastCount}`);
                print("Collection info: " +
                      tojson(coll.getDB().getCollectionInfos({name: coll.getName()})));
                print("Collection stats: " + tojson(coll.stats()));
                print("First 10 documents in collection: " +
                      tojson(coll.find().limit(10).toArray()));

                // TODO (SERVER-35483): Remove this block and enable fastcount checks.
                if (coll.getFullName() == "config.transactions") {
                    print(`Ignoring fastcount error for ${coll.getFullName()} on ` +
                          `${coll.getMongo().host}. itcount: ${itCount}, fast count: ${fastCount}`);
                    return;
                }
                success = false;
            }
        }

        function checkCollectionCountsForDB(_db) {
            const res = assert.commandWorked(
                _db.runCommand({listCollections: 1, includePendingDrops: true}));
            const collNames = new DBCommandCursor(_db, res).toArray();
            collNames.forEach(c => checkCollectionCount(_db.getCollection(c.name)));
        }

        function checkCollectionCountsForNode(node) {
            const dbNames = node.getDBNames();
            dbNames.forEach(dbName => checkCollectionCountsForDB(node.getDB(dbName)));
        }

        function checkCollectionCountsForReplSet(rst) {
            rst.nodes.forEach(node => checkCollectionCountsForNode(node));
            assert(success, `Collection counts did not match. search for '${errPrefix}' in logs.`);
        }

        this.checkReplicaSet(checkCollectionCountsForReplSet, null, this);
    };

    /**
     * Starts up a server.  Options are saved by default for subsequent starts.
     *
     *
     * Options { remember : true } re-applies the saved options from a prior start.
     * Options { noRemember : true } ignores the current properties.
     * Options { appendOptions : true } appends the current options to those remembered.
     * Options { startClean : true } clears the data directory before starting.
     *
     * @param {int|conn|[int|conn]} n array or single server number (0, 1, 2, ...) or conn
     * @param {object} [options]
     * @param {boolean} [restart] If false, the data directory will be cleared
     *   before the server starts.  Default: false.
     *
     */
    this.start = function(n, options, restart, wait) {
        if (n.length) {
            var nodes = n;
            var started = [];

            for (var i = 0; i < nodes.length; i++) {
                if (this.start(nodes[i], Object.merge({}, options), restart, wait)) {
                    started.push(nodes[i]);
                }
            }

            return started;
        }

        // TODO: should we do something special if we don't currently know about this node?
        n = this.getNodeId(n);

        print("ReplSetTest n is : " + n);

        var defaults = {
            useHostName: this.useHostName,
            oplogSize: this.oplogSize,
            keyFile: this.keyFile,
            port: _useBridge ? _unbridgedPorts[n] : this.ports[n],
            replSet: this.useSeedList ? this.getURL() : this.name,
            dbpath: "$set-$node"
        };

        //
        // Note : this replaces the binVersion of the shared startSet() options the first time
        // through, so the full set is guaranteed to have different versions if size > 1.  If using
        // start() independently, independent version choices will be made
        //
        if (options && options.binVersion) {
            options.binVersion = MongoRunner.versionIterator(options.binVersion);
        }

        // If restarting a node, use its existing options as the defaults.
        var baseOptions;
        if ((options && options.restart) || restart) {
            baseOptions = _useBridge ? _unbridgedNodes[n].fullOptions : this.nodes[n].fullOptions;
        } else {
            baseOptions = defaults;
        }
        baseOptions = Object.merge(baseOptions, this.nodeOptions["n" + n]);
        options = Object.merge(baseOptions, options);
        if (options.hasOwnProperty("rsConfig")) {
            this.nodeOptions["n" + n] =
                Object.merge(this.nodeOptions["n" + n], {rsConfig: options.rsConfig});
        }
        delete options.rsConfig;

        options.restart = options.restart || restart;

        var pathOpts = {node: n, set: this.name};
        options.pathOpts = Object.merge(options.pathOpts || {}, pathOpts);

        // Turn off periodic noop writes for replica sets by default.
        options.setParameter = options.setParameter || {};
        if (typeof (options.setParameter) === "string") {
            var eqIdx = options.setParameter.indexOf("=");
            if (eqIdx != -1) {
                var param = options.setParameter.substring(0, eqIdx);
                var value = options.setParameter.substring(eqIdx + 1);
                options.setParameter = {};
                options.setParameter[param] = value;
            }
        }
        options.setParameter.writePeriodicNoops = options.setParameter.writePeriodicNoops || false;

        // We raise the number of initial sync connect attempts for tests that disallow chaining.
        // Disabling chaining can cause sync source selection to take longer so we must increase
        // the number of connection attempts.
        options.setParameter.numInitialSyncConnectAttempts =
            options.setParameter.numInitialSyncConnectAttempts || 60;

        if (tojson(options) != tojson({}))
            printjson(options);

        print("ReplSetTest " + (restart ? "(Re)" : "") + "Starting....");

        if (_useBridge && (restart === undefined || !restart)) {
            // We leave the mongobridge process running when the mongod process is restarted so we
            // don't need to start a new one.
            var bridgeOptions = Object.merge(_bridgeOptions, options.bridgeOptions || {});
            bridgeOptions = Object.merge(bridgeOptions, {
                hostName: this.host,
                port: this.ports[n],
                // The mongod processes identify themselves to mongobridge as host:port, where the
                // host is the actual hostname of the machine and not localhost.
                dest: getHostName() + ":" + _unbridgedPorts[n],
            });

            if (jsTestOptions().networkMessageCompressors) {
                bridgeOptions["networkMessageCompressors"] =
                    jsTestOptions().networkMessageCompressors;
            }

            this.nodes[n] = new MongoBridge(bridgeOptions);
        }

        var conn = MongoRunner.runMongod(options);
        if (!conn) {
            throw new Error("Failed to start node " + n);
        }

        // Make sure to call _addPath, otherwise folders won't be cleaned.
        this._addPath(conn.dbpath);

        if (_useBridge) {
            this.nodes[n].connectToBridge();
            _unbridgedNodes[n] = conn;
        } else {
            this.nodes[n] = conn;
        }

        // Add replica set specific attributes.
        this.nodes[n].nodeId = n;

        printjson(this.nodes);

        // Clean up after noReplSet to ensure it doesn't effect future restarts.
        if (options.noReplSet) {
            this.nodes[n].fullOptions.replSet = defaults.replSet;
            delete this.nodes[n].fullOptions.noReplSet;
        }

        wait = wait || false;
        if (!wait.toFixed) {
            if (wait)
                wait = 0;
            else
                wait = -1;
        }

        if (wait >= 0) {
            // Wait for node to start up.
            _waitForHealth(this.nodes[n], Health.UP, wait);
        }

        if (_causalConsistency) {
            this.nodes[n].setCausalConsistency(true);
        }

        return this.nodes[n];
    };

    /**
     * Restarts a db without clearing the data directory by default, and using the node(s)'s
     * original startup options by default.
     *
     * Option { startClean : true } forces clearing the data directory.
     * Option { auth : Object } object that contains the auth details for admin credentials.
     *   Should contain the fields 'user' and 'pwd'
     *
     * In order not to use the original startup options, use stop() (or stopSet()) followed by
     * start() (or startSet()) without passing restart: true as part of the options.
     *
     * @param {int|conn|[int|conn]} n array or single server number (0, 1, 2, ...) or conn
     */
    this.restart = function(n, options, signal, wait) {
        // Can specify wait as third parameter, if using default signal
        if (signal == true || signal == false) {
            wait = signal;
            signal = undefined;
        }

        this.stop(n, signal, options, {forRestart: true});

        var started = this.start(n, options, true, wait);

        if (jsTestOptions().keyFile) {
            if (started.length) {
                // if n was an array of conns, start will return an array of connections
                for (var i = 0; i < started.length; i++) {
                    assert(jsTest.authenticate(started[i]), "Failed authentication during restart");
                }
            } else {
                assert(jsTest.authenticate(started), "Failed authentication during restart");
            }
        }
        return started;
    };

    this.stopMaster = function(signal, opts) {
        var master = this.getPrimary();
        var master_id = this.getNodeId(master);
        return this.stop(master_id, signal, opts);
    };

    /**
     * Stops a particular node or nodes, specified by conn or id
     *
     * If _useBridge=true, then the mongobridge process(es) corresponding to the node(s) are also
     * terminated unless forRestart=true. The mongobridge process(es) are left running across
     * restarts to ensure their configuration remains intact.
     *
     * @param {number|Mongo} n the index or connection object of the replica set member to stop.
     * @param {number} signal the signal number to use for killing
     * @param {Object} opts @see MongoRunner.stopMongod
     * @param {Object} [extraOptions={}]
     * @param {boolean} [extraOptions.forRestart=false] indicates whether stop() is being called
     * with the intent to call start() with restart=true for the same node(s) n.
     */
    this.stop = function(n, signal, opts, {forRestart: forRestart = false} = {}) {
        // Flatten array of nodes to stop
        if (n.length) {
            var nodes = n;

            var stopped = [];
            for (var i = 0; i < nodes.length; i++) {
                if (this.stop(nodes[i], signal, opts))
                    stopped.push(nodes[i]);
            }

            return stopped;
        }

        // Can specify wait as second parameter, if using default signal
        if (signal == true || signal == false) {
            signal = undefined;
        }

        n = this.getNodeId(n);

        var conn = _useBridge ? _unbridgedNodes[n] : this.nodes[n];
        print('ReplSetTest stop *** Shutting down mongod in port ' + conn.port + ' ***');
        var ret = MongoRunner.stopMongod(conn, signal, opts);

        print('ReplSetTest stop *** Mongod in port ' + conn.port + ' shutdown with code (' + ret +
              ') ***');

        if (_useBridge && !forRestart) {
            // We leave the mongobridge process running when the mongod process is being restarted.
            const bridge = this.nodes[n];
            print('ReplSetTest stop *** Shutting down mongobridge on port ' + bridge.port + ' ***');
            const exitCode = bridge.stop();  // calls MongoBridge#stop()
            print('ReplSetTest stop *** mongobridge on port ' + bridge.port +
                  ' exited with code (' + exitCode + ') ***');
        }

        return ret;
    };

    /**
     * Kill all members of this replica set.
     *
     * @param {number} signal The signal number to use for killing the members
     * @param {boolean} forRestart will not cleanup data directory
     * @param {Object} opts @see MongoRunner.stopMongod
     */
    this.stopSet = function(signal, forRestart, opts) {
        // Check to make sure data is the same on all nodes.
        if (!jsTest.options().skipCheckDBHashes) {
            print("ReplSetTest stopSet going to run data consistency checks.");
            // To skip this check add TestData.skipCheckDBHashes = true;
            // Reasons to skip this test include:
            // - the primary goes down and none can be elected (so fsync lock/unlock commands fail)
            // - the replica set is in an unrecoverable inconsistent state. E.g. the replica set
            //   is partitioned.
            //
            let master = _callIsMaster();
            if (master && this._liveNodes.length > 1) {  // skip for sets with 1 live node
                // Auth only on live nodes because authutil.assertAuthenticate
                // refuses to log in live connections if some secondaries are down.
                print("ReplSetTest stopSet checking oplogs.");
                asCluster(this._liveNodes, () => this.checkOplogs());
                print("ReplSetTest stopSet checking replicated data hashes.");
                asCluster(this._liveNodes, () => this.checkReplicatedDataHashes());
            } else {
                print(
                    "ReplSetTest stopSet skipped data consistency checks. Number of _liveNodes: " +
                    this._liveNodes.length + ", _callIsMaster response: " + master);
            }
            print("ReplSetTest stopSet finished data consistency checks.");
        }

        // Make shutdown faster in tests, especially when election handoff has no viable candidate.
        // Ignore errors from setParameter, perhaps it's a pre-4.1.10 mongod.
        if (_callIsMaster()) {
            asCluster(this._liveNodes, () => {
                for (let node of this._liveNodes) {
                    try {
                        print(
                            "ReplSetTest stopSet disabling 'waitForStepDownOnNonCommandShutdown' on " +
                            node.host);
                        assert.commandWorked(node.adminCommand({
                            setParameter: 1,
                            waitForStepDownOnNonCommandShutdown: false,
                        }));
                    } catch (e) {
                        print("Error in setParameter for waitForStepDownOnNonCommandShutdown:");
                        print(e);
                    }
                }
            });
        }

        print("ReplSetTest stopSet stopping all replica set nodes.");
        for (var i = 0; i < this.ports.length; i++) {
            this.stop(i, signal, opts);
        }
        print("ReplSetTest stopSet stopped all replica set nodes.");

        if (forRestart) {
            print("ReplSetTest stopSet returning since forRestart=true.");
            return;
        }

        if ((!opts || !opts.noCleanData) && _alldbpaths) {
            print("ReplSetTest stopSet deleting all dbpaths");
            for (var i = 0; i < _alldbpaths.length; i++) {
                print("ReplSetTest stopSet deleting dbpath: " + _alldbpaths[i]);
                resetDbpath(_alldbpaths[i]);
            }
            print("ReplSetTest stopSet deleted all dbpaths");
        }

        _forgetReplSet(this.name);

        print('ReplSetTest stopSet *** Shut down repl set - test worked ****');
    };

    /**
     * Returns whether or not this ReplSetTest uses mongobridge.
     */
    this.usesBridge = function() {
        return _useBridge;
    };

    /**
     * Wait for a state indicator to go to a particular state or states.
     *
     * Note that this waits for the state as indicated by the primary node.  If you want to wait for
     * a node to actually reach SECONDARY state, as reported by itself, use awaitSecondaryNodes
     * instead.
     *
     * @param node is a single node or list of nodes, by id or conn
     * @param state is a single state or list of states
     * @param timeout how long to wait for the state to be reached
     * @param reconnectNode indicates that we should reconnect to a node that stepped down
     *
     */
    this.waitForState = function(node, state, timeout, reconnectNode) {
        _waitForIndicator(node, state, "state", timeout, reconnectNode);
    };

    /**
     * Waits until there is a master node.
     */
    this.waitForMaster = function(timeout) {
        var master;
        assert.soonNoExcept(function() {
            return (master = self.getPrimary());
        }, "waiting for master", timeout);

        return master;
    };

    //
    // ReplSetTest constructors
    //

    /**
     * Constructor, which initializes the ReplSetTest object by starting new instances.
     */
    function _constructStartNewInstances(opts) {
        self.name = opts.name || jsTest.name();
        print('Starting new replica set ' + self.name);

        self.useHostName = opts.useHostName == undefined ? true : opts.useHostName;
        self.host = self.useHostName ? (opts.host || getHostName()) : 'localhost';
        self.oplogSize = opts.oplogSize || 40;
        self.useSeedList = opts.useSeedList || false;
        self.keyFile = opts.keyFile;
        self.protocolVersion = opts.protocolVersion;
        self.waitForKeys = opts.waitForKeys;

        _useBridge = opts.useBridge || false;
        _bridgeOptions = opts.bridgeOptions || {};

        _causalConsistency = opts.causallyConsistent || false;

        _configSettings = opts.settings || false;

        self.nodeOptions = {};

        var numNodes;

        if (isObject(opts.nodes)) {
            var len = 0;
            for (var i in opts.nodes) {
                var options = self.nodeOptions["n" + len] =
                    Object.merge(opts.nodeOptions, opts.nodes[i]);
                if (i.startsWith("a")) {
                    options.arbiter = true;
                }

                len++;
            }

            numNodes = len;
        } else if (Array.isArray(opts.nodes)) {
            for (var i = 0; i < opts.nodes.length; i++) {
                self.nodeOptions["n" + i] = Object.merge(opts.nodeOptions, opts.nodes[i]);
            }

            numNodes = opts.nodes.length;
        } else {
            for (var i = 0; i < opts.nodes; i++) {
                self.nodeOptions["n" + i] = opts.nodeOptions;
            }

            numNodes = opts.nodes;
        }

        if (_useBridge) {
            let makeAllocatePortFn = (preallocatedPorts) => {
                let idxNextNodePort = 0;

                return function() {
                    if (idxNextNodePort >= preallocatedPorts.length) {
                        throw new Error("Cannot use a replica set larger than " +
                                        preallocatedPorts.length + " members with useBridge=true");
                    }

                    const nextPort = preallocatedPorts[idxNextNodePort];
                    ++idxNextNodePort;
                    return nextPort;
                };
            };

            _allocatePortForBridge = makeAllocatePortFn(allocatePorts(MongoBridge.kBridgeOffset));
            _allocatePortForNode = makeAllocatePortFn(allocatePorts(MongoBridge.kBridgeOffset));
        } else {
            _allocatePortForBridge = function() {
                throw new Error("Using mongobridge isn't enabled for this replica set");
            };
            _allocatePortForNode = allocatePort;
        }

        self.nodes = [];

        if (_useBridge) {
            self.ports = Array.from({length: numNodes}, _allocatePortForBridge);
            _unbridgedPorts = Array.from({length: numNodes}, _allocatePortForNode);
            _unbridgedNodes = [];
        } else {
            self.ports = Array.from({length: numNodes}, _allocatePortForNode);
        }
    }

    /**
     * Constructor, which instantiates the ReplSetTest object from an existing set.
     */
    function _constructFromExistingSeedNode(seedNode) {
        const conn = new Mongo(seedNode);
        if (jsTest.options().keyFile) {
            self.keyFile = jsTest.options().keyFile;
        }
        var conf = asCluster(conn, () => _replSetGetConfig(conn));
        print('Recreating replica set from config ' + tojson(conf));

        var existingNodes = conf.members.map(member => member.host);
        self.ports = existingNodes.map(node => node.split(':')[1]);
        self.nodes = existingNodes.map(node => new Mongo(node));
        self.waitForKeys = false;
        self.host = existingNodes[0].split(':')[0];
        self.name = conf._id;
    }

    if (typeof opts === 'string' || opts instanceof String) {
        retryOnNetworkError(function() {
            // The primary may unexpectedly step down during startup if under heavy load
            // and too slowly processing heartbeats. When it steps down, it closes all of
            // its connections.
            _constructFromExistingSeedNode(opts);
        }, 60);
    } else {
        _constructStartNewInstances(opts);
    }
};

/**
 *  Global default timeout (10 minutes).
 */
ReplSetTest.kDefaultTimeoutMS = 10 * 60 * 1000;

/**
 * Set of states that the replica set can be in. Used for the wait functions.
 */
ReplSetTest.State = {
    PRIMARY: 1,
    SECONDARY: 2,
    RECOVERING: 3,
    // Note there is no state 4
    STARTUP_2: 5,
    UNKNOWN: 6,
    ARBITER: 7,
    DOWN: 8,
    ROLLBACK: 9,
    REMOVED: 10,
};

ReplSetTest.OpTimeType = {
    LAST_APPLIED: 1,
    LAST_DURABLE: 2,
};