mongo/jstests/multiVersion/genericSetFCVUsage/downgrade_after_rollback_via_refetch.js

// When enableMajorityReadConcern=false, a node transitions from ROLLBACK to RECOVERING with an
// unstable checkpoint with appliedThrough set to the common point. Test that if the node crashes
// and restarts with the last-stable version before its next stable checkpoint, then oplog entries
// after the common point are replayed.
(function() {
    "use strict";

    load("jstests/libs/feature_compatibility_version.js");
    load("jstests/replsets/libs/rollback_test.js");

    TestData.rollbackShutdowns = true;
    TestData.allowUncleanShutdowns = true;
    let name = "downgrade_after_rollback_via_refetch";
    let dbName = "test";
    let sourceCollName = "coll";

    function testDowngrade(enableMajorityReadConcern) {
        jsTest.log("Test downgrade with enableMajorityReadConcern=" + enableMajorityReadConcern);

        // Set up Rollback Test.
        let replTest = new ReplSetTest(
            {name, nodes: 3, useBridge: true, nodeOptions: {enableMajorityReadConcern: "false"}});
        replTest.startSet();
        let config = replTest.getReplSetConfig();
        config.members[2].priority = 0;
        config.settings = {chainingAllowed: false};
        replTest.initiate(config);
        let rollbackTest = new RollbackTest(name, replTest);

        // Set the featureCompatibilityVersion to the last-stable version, so that we can downgrade
        // the rollback node.
        assert.commandWorked(rollbackTest.getPrimary().adminCommand(
            {setFeatureCompatibilityVersion: lastStableFCV}));

        let rollbackNode = rollbackTest.transitionToRollbackOperations();

        // Turn off stable checkpoints on the rollback node.
        assert.commandWorked(rollbackNode.adminCommand(
            {configureFailPoint: "disableSnapshotting", mode: "alwaysOn"}));

        // Wait for a rollback to finish.
        rollbackTest.transitionToSyncSourceOperationsBeforeRollback();
        rollbackTest.transitionToSyncSourceOperationsDuringRollback();
        rollbackTest.transitionToSteadyStateOperations();

        // Replicate a new operation to the rollback node. Replication is disabled on the tiebreaker
        // node, so a successful majority write guarantees the write has replicated to the rollback
        // node.
        assert.commandWorked(rollbackTest.getPrimary().getDB(dbName)[sourceCollName].insert(
            {_id: 0}, {writeConcern: {w: "majority"}}));
        assert.eq(rollbackNode.getDB(dbName)[sourceCollName].find({_id: 0}).itcount(), 1);

        // Kill the rollback node and restart it on the last-stable version.
        rollbackTest.restartNode(
            0,
            9,
            {binVersion: "last-stable", enableMajorityReadConcern: enableMajorityReadConcern});
        replTest.awaitSecondaryNodes();

        // The rollback node should replay the new operation.
        rollbackNode = rollbackTest.getSecondary();
        assert.eq(rollbackNode.getDB(dbName)[sourceCollName].find({_id: 0}).itcount(), 1);

        rollbackTest.stop();
    }

    testDowngrade("true");
    testDowngrade("false");
})();