mongodb/jstests/noPassthrough/replica_set_connection_stepdown.js

/**
 * Tests that DBClientRS doesn't do any re-targeting on replica set member state changes until it
 * sees a "not master" error response from a command.
 * @tags: [requires_replication]
 */
(function() {
    "use strict";

    const rst = new ReplSetTest({nodes: 1});
    rst.startSet();
    rst.initiate();

    const directConn = rst.getPrimary();
    const rsConn = new Mongo(rst.getURL());
    assert(rsConn.isReplicaSetConnection(),
           "expected " + rsConn.host + " to be a replica set connection string");

    function stepDownPrimary(rst) {
        const awaitShell = startParallelShell(
            () => assert.commandWorked(db.adminCommand({replSetStepDown: 60, force: true})),
            directConn.port);

        // We wait for the primary to transition to the SECONDARY state to ensure we're waiting
        // until after the parallel shell has started the replSetStepDown command and the server is
        // paused at the failpoint. Do not attempt to reconnect to the node, since the node will be
        // holding the global X lock at the failpoint.
        const reconnectNode = false;
        rst.waitForState(directConn, ReplSetTest.State.SECONDARY, null, reconnectNode);

        return awaitShell;
    }

    const failpoint = "stepdownHangBeforePerformingPostMemberStateUpdateActions";
    assert.commandWorked(
        directConn.adminCommand({configureFailPoint: failpoint, mode: "alwaysOn"}));

    const awaitShell = stepDownPrimary(rst);

    const error = assert.throws(function() {
        // DBClientRS will continue to send command requests to the node it believed to be primary
        // even after it stepped down so long as it hasn't closed its connection. But this may also
        // throw if the ReplicaSetMonitor's backgroud refresh has already noticed that this node is
        // no longer primary.
        assert.commandFailedWithCode(rsConn.getDB("test").runCommand({find: "mycoll"}),
                                     ErrorCodes.NotMasterNoSlaveOk);

        // However, once the server responds back with a "not master" error, DBClientRS will cause
        // the ReplicaSetMonitor to attempt to discover the current primary, which will cause this
        // to definitely throw.
        rsConn.getDB("test").runCommand({find: "mycoll"});
    });
    assert(/Could not find host/.test(error.toString()),
           "find command failed for a reason other than being unable to discover a new primary: " +
               tojson(error));

    try {
        assert.commandWorked(directConn.adminCommand({configureFailPoint: failpoint, mode: "off"}));
    } catch (e) {
        if (!isNetworkError(e)) {
            throw e;
        }

        // We ignore network errors because it's possible that depending on how quickly the server
        // closes connections that the connection would get closed before the server has a chance to
        // respond to the configureFailPoint command with ok=1.
    }

    awaitShell();
    rst.stopSet();
})();