SERVER-33068 Fix run_check_repl_dbhash.js hook to actually run dbhash.

Consolidates the logic in the run_check_repl_dbhash.js and
run_validate_collections.js for discovering all of the mongod processes
in a MongoDB deployment into a new discover_topology.js library.

Also adds a test that relies on mongod logging to verify that the
run_check_repl_dbhash.js and run_validate_collections.js hooks execute
on all of the expected servers.

1 files changed, 102 insertions, 0 deletions

diff --git a/jstests/libs/discover_topology.js b/jstests/libs/discover_topology.js
new file mode 100644
index 00000000000..95b072894b0
--- /dev/null
+++ b/jstests/libs/discover_topology.js
@@ -0,0 +1,102 @@
+'use strict';
+
+// The tojson() function that is commonly used to build up assertion messages doesn't support the
+// Symbol type, so we just use unique string values instead.
+var Topology = {
+    kStandalone: 'stand-alone',
+    kReplicaSet: 'replica set',
+    kShardedCluster: 'sharded cluster',
+};
+
+var DiscoverTopology = (function() {
+    const kDefaultConnectFn = (host) => new Mongo(host);
+
+    function getDataMemberConnectionStrings(conn) {
+        const res = conn.adminCommand({isMaster: 1});
+
+        if (!res.hasOwnProperty('setName')) {
+            // 'conn' represents a connection to a stand-alone mongod.
+            return {type: Topology.kStandalone, mongod: conn.host};
+        }
+
+        // The "passives" field contains the list of unelectable (priority=0) secondaries
+        // and is omitted from the server's response when there are none.
+        res.passives = res.passives || [];
+        return {type: Topology.kReplicaSet, nodes: [...res.hosts, ...res.passives]};
+    }
+
+    function findConnectedNodesViaMongos(conn, options) {
+        function getConfigServerConnectionString() {
+            const shardMap = conn.adminCommand({getShardMap: 1});
+
+            if (!shardMap.hasOwnProperty('map')) {
+                throw new Error(
+                    'Expected "getShardMap" command to return an object with a "map" field: ' +
+                    tojson(shardMap));
+            }
+
+            if (!shardMap.map.hasOwnProperty('config')) {
+                throw new Error(
+                    'Expected "getShardMap" command to return an object with a "map.config"' +
+                    ' field: ' + tojson(shardMap));
+            }
+
+            return shardMap.map.config;
+        }
+
+        const connectFn =
+            options.hasOwnProperty('connectFn') ? options.connectFn : kDefaultConnectFn;
+
+        const configsvrConn = connectFn(getConfigServerConnectionString());
+        const configsvrHosts = getDataMemberConnectionStrings(configsvrConn);
+
+        const shards = assert.commandWorked(conn.adminCommand({listShards: 1})).shards;
+        const shardHosts = {};
+
+        for (let shardInfo of shards) {
+            const shardConn = connectFn(shardInfo.host);
+            shardHosts[shardInfo._id] = getDataMemberConnectionStrings(shardConn);
+        }
+
+        return {type: Topology.kShardedCluster, configsvr: configsvrHosts, shards: shardHosts};
+    }
+
+    return {
+        /**
+         * Returns an object describing the topology of the mongod processes reachable from 'conn'.
+         * The "connectFn" property can be optionally specified to support custom retry logic when
+         * making connection attempts without overriding the Mongo constructor itself.
+         *
+         * For a stand-alone mongod, an object of the form
+         *   {type: Topology.kStandalone, mongod: <conn-string>}
+         * is returned.
+         *
+         * For a replica set, an object of the form
+         *   {type: Topology.kReplicaSet, nodes: [<conn-string1>, <conn-string2>, ...]}
+         * is returned.
+         *
+         * For a sharded cluster, an object of the form
+         *   {
+         *     type: Topology.kShardedCluster,
+         *     configsvr: {nodes: [...]},
+         *     shards: {
+         *       <shard-name1>: {type: Topology.kStandalone, mongod: ...},
+         *       <shard-name2>: {type: Topology.kReplicaSet, nodes: [...]},
+         *       ...
+         *     }
+         *   }
+         * is returned, where the description for each shard depends on whether it is a stand-alone
+         * shard or a replica set shard.
+         */
+        findConnectedNodes: function findConnectedNodes(conn,
+                                                        options = {connectFn: kDefaultConnectFn}) {
+            const isMongod = conn.adminCommand({isMaster: 1}).msg !== 'isdbgrid';
+
+            if (isMongod) {
+                return getDataMemberConnectionStrings(conn);
+            }
+
+            return findConnectedNodesViaMongos(conn, options);
+        },
+    };
+})();