1 files changed, 208 insertions, 0 deletions
diff --git a/jstests/replsets/last_vote.js b/jstests/replsets/last_vote.js
new file mode 100644
index 00000000000..bbb38bd4af3
--- /dev/null
+++ b/jstests/replsets/last_vote.js
@@ -0,0 +1,208 @@
+// 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();
+
+    // Lower the election timeout to make the test run faster since it waits for multiple elections.
+    var conf = rst.getReplSetConfig();
+    conf.settings = {
+        electionTimeoutMillis: 3000,
+    };
+    rst.initiate(conf);
+
+    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.writeOK(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");
+
+    for (var i = 0; i < 3; i++) {
+        var primary = rst.getPrimary();
+        var term = getLatestOp(primary).t;
+        jsTestLog("Last vote should have term: " + term + " and candidate: " + primary.host +
+                  ", index: " + rst.getNodeId(primary));
+        rst.nodes.forEach(function(node) {
+            assertNodeHasLastVote(node, term, primary);
+        });
+        assert.throws(function() {
+            primary.adminCommand({replSetStepDown: 5, force: true});
+        });
+        rst.waitForState(primary, ReplSetTest.State.SECONDARY);
+    }
+
+    var term = getLatestOp(rst.getPrimary()).t + 100;
+
+    jsTestLog("Test that last vote is loaded on startup");
+    jsTestLog("Reconfiguring cluster to make node 0 unelectable so it stays SECONDARY on restart");
+    conf = rst.getReplSetConfigFromNode();
+    conf.version++;
+    conf.members[0].priority = 0;
+    reconfig(rst, conf);
+
+    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.
+    assertCurrentTerm(node0, term);
+
+    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: 2,
+        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));
+    assert.eq(response.reason,
+              "candidate's term is lower than mine",
+              "replSetRequestVotes response had the wrong reason: " + 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: 2,
+        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: 2,
+        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));
+    assert.eq(response.reason,
+              "already voted for another candidate this term",
+              "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 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: 2,
+        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: 2,
+        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();
+})();