// Tests that the last vote document is stored during elections and that it is loaded and used on
// startup.
//
// The test first runs a few elections and checks that the lastVote document is set correctly
// after each one.
//
// The test then restarts one node as a standalone, changes its last vote doc, and stops the
// other node. It then restarts the first node as a replicaset and manually runs
// replSetRequestVotes commands against it and checks that its response is correct.
//
// @tags: [requires_persistence]

(function() {
"use strict";
load("jstests/replsets/rslib.js");  // For getLatestOp()

var name = "last_vote";
var rst = new ReplSetTest({
    name: name,
    nodes: 2,
});
rst.startSet();
// Initiate the set with a high election timeout so that there aren't any unplanned elections.
rst.initiateWithHighElectionTimeout();

const lastVoteNS = 'local.replset.election';

function getLastVoteDoc(conn) {
    assert.eq(conn.getCollection(lastVoteNS).find().itcount(), 1, 'last vote should be singleton');
    return conn.getCollection(lastVoteNS).findOne();
}

function setLastVoteDoc(conn, term, candidate) {
    var newLastVote = {term: term, candidateIndex: rst.getNodeId(candidate)};
    return assert.commandWorked(conn.getCollection(lastVoteNS).update({}, newLastVote));
}

function assertNodeHasLastVote(node, term, candidate) {
    var lastVoteDoc = getLastVoteDoc(node);
    assert.eq(lastVoteDoc.term, term, node.host + " had wrong last vote term.");
    assert.eq(lastVoteDoc.candidateIndex,
              rst.getNodeId(candidate),
              node.host + " had wrong last vote candidate.");
}

function assertCurrentTerm(node, term) {
    var stat = assert.commandWorked(node.adminCommand({replSetGetStatus: 1}));
    assert.eq(stat.term, term, "Term changed when it should not have");
}

jsTestLog("Test that last vote is set on successive elections");

// Run a few successive elections, alternating who becomes primary.
var numElections = 3;
for (var i = 0; i < numElections; i++) {
    var primary = rst.getPrimary();
    var secondary = rst.getSecondary();
    var term = getLatestOp(primary).t;

    // SERVER-20844 ReplSetTest starts up a single node replica set then reconfigures to the
    // correct size, so secondaries didn't vote in the first election.
    if (i > 0) {
        jsTestLog("Last vote should have term: " + term + " and candidate: " + primary.host +
                  ", index: " + rst.getNodeId(primary));
        rst.nodes.forEach(function(node) {
            assertNodeHasLastVote(node, term, primary);
        });
    }

    rst.stepUp(secondary);

    // Make sure a new primary has been established.
    rst.waitForState(primary, ReplSetTest.State.SECONDARY);
    rst.waitForState(secondary, ReplSetTest.State.PRIMARY);

    // Reset election timeout for the old primary.
    assert.commandWorked(primary.adminCommand({replSetFreeze: 0}));
}

var term = getLatestOp(rst.getPrimary()).t + 100;

jsTestLog("Test that last vote is loaded on startup");

// Ensure that all ops are replicated before stepping up node 1.
rst.awaitReplication();

// We cannot reconfig node 0 to have priority 0 if it is currently the primary,
// so we make sure node 1 is primary.
jsTestLog("Stepping up node 1");
rst.stepUp(rst.nodes[1]);

jsTestLog("Reconfiguring cluster to make node 0 unelectable so it stays SECONDARY on restart");
let conf = rst.getReplSetConfigFromNode();
conf.version++;
conf.members[0].priority = 0;
reconfig(rst, conf);
rst.awaitNodesAgreeOnConfigVersion();

jsTestLog("Restarting node 0 as a standalone");
var node0 = rst.restart(0, {noReplSet: true});  // Restart as a standalone node.
jsTestLog("Stopping node 1");
rst.stop(1);  // Stop node 1 so that node 0 controls the term by itself.
jsTestLog("Setting the lastVote on node 0 to term: " + term + " candidate: " + rst.nodes[0].host +
          ", index: 0");
setLastVoteDoc(node0, term, rst.nodes[0]);

jsTestLog("Restarting node 0 in replica set mode");
node0 = rst.restart(0);  // Restart in replSet mode again.
rst.waitForState(node0, ReplSetTest.State.SECONDARY);

assert.soonNoExcept(function() {
    assertCurrentTerm(node0, term);
    return true;
});

jsTestLog("Manually sending node 0 a dryRun replSetRequestVotes command, " +
          "expecting failure in old term");
var response = assert.commandWorked(node0.adminCommand({
    replSetRequestVotes: 1,
    setName: name,
    dryRun: true,
    term: term - 1,
    candidateIndex: 1,
    configVersion: conf.version,
    lastCommittedOp: getLatestOp(node0)
}));
assert.eq(
    response.term, term, "replSetRequestVotes response had the wrong term: " + tojson(response));
assert(!response.voteGranted,
       "node granted vote in term before last vote doc: " + tojson(response));
assertNodeHasLastVote(node0, term, rst.nodes[0]);
assertCurrentTerm(node0, term);

jsTestLog("Manually sending node 0 a dryRun replSetRequestVotes command in same term, " +
          "expecting success but no recording of lastVote");
response = assert.commandWorked(node0.adminCommand({
    replSetRequestVotes: 1,
    setName: name,
    dryRun: true,
    term: term,
    candidateIndex: 1,
    configVersion: conf.version,
    lastCommittedOp: getLatestOp(node0)
}));
assert.eq(
    response.term, term, "replSetRequestVotes response had the wrong term: " + tojson(response));
assert(response.voteGranted,
       "node failed to grant dryRun vote in term equal to last vote doc: " + tojson(response));
assert.eq(
    response.reason, "", "replSetRequestVotes response had the wrong reason: " + tojson(response));
assertNodeHasLastVote(node0, term, rst.nodes[0]);
assertCurrentTerm(node0, term);

jsTestLog("Manually sending node 0 a replSetRequestVotes command, expecting failure in same term");
response = assert.commandWorked(node0.adminCommand({
    replSetRequestVotes: 1,
    setName: name,
    dryRun: false,
    term: term,
    candidateIndex: 1,
    configVersion: conf.version,
    lastCommittedOp: getLatestOp(node0)
}));
assert.eq(
    response.term, term, "replSetRequestVotes response had the wrong term: " + tojson(response));
assert(!response.voteGranted, "node granted vote in term of last vote doc: " + tojson(response));
assertNodeHasLastVote(node0, term, rst.nodes[0]);
assertCurrentTerm(node0, term);

jsTestLog("Manually sending node 0 a replSetRequestVotes command, " +
          "expecting success with a recording of the new lastVote");
response = assert.commandWorked(node0.adminCommand({
    replSetRequestVotes: 1,
    setName: name,
    dryRun: false,
    term: term + 1,
    candidateIndex: 1,
    configVersion: conf.version,
    lastCommittedOp: getLatestOp(node0)
}));
assert.eq(response.term,
          term + 1,
          "replSetRequestVotes response had the wrong term: " + tojson(response));
assert(response.voteGranted,
       "node failed to grant vote in term greater than last vote doc: " + tojson(response));
assert.eq(
    response.reason, "", "replSetRequestVotes response had the wrong reason: " + tojson(response));
assertNodeHasLastVote(node0, term + 1, rst.nodes[1]);
assertCurrentTerm(node0, term + 1);

jsTestLog("Manually sending node 0 a dryRun replSetRequestVotes command in future term, " +
          "expecting success but no recording of lastVote");
response = assert.commandWorked(node0.adminCommand({
    replSetRequestVotes: 1,
    setName: name,
    dryRun: true,
    term: term + 2,
    candidateIndex: 1,
    configVersion: conf.version,
    lastCommittedOp: getLatestOp(node0)
}));
assert.eq(response.term,
          term + 2,
          "replSetRequestVotes response had the wrong term: " + tojson(response));
assert(response.voteGranted,
       "node failed to grant vote in term greater than last vote doc: " + tojson(response));
assert.eq(
    response.reason, "", "replSetRequestVotes response had the wrong reason: " + tojson(response));
assertNodeHasLastVote(node0, term + 1, rst.nodes[1]);
assertCurrentTerm(node0, term + 2);

rst.stopSet();
})();