mongodb/jstests/sharding/explain_read_pref.js

/**
 * Tests read preference for explain command.
 *
 * Test is loosely based from read_pref_cmd.js.
 */

load("jstests/replsets/rslib.js");

var NODE_COUNT = 2;

var testAllModes = function(conn, isMongos) {

    // The primary is tagged with { tag: 'one' } and the secondary with
    // { tag: 'two' } so we can test the interaction of modes and tags. Test
    // a bunch of combinations.
    [
        // mode, tagSets, expectedHost
        ['primary', undefined, false],
        ['primary', [{}], false],

        ['primaryPreferred', undefined, false],
        ['primaryPreferred', [{tag: 'one'}], false],
        // Correctly uses primary and ignores the tag
        ['primaryPreferred', [{tag: 'two'}], false],

        ['secondary', undefined, true],
        ['secondary', [{tag: 'two'}], true],
        ['secondary', [{tag: 'doesntexist'}, {}], true],
        ['secondary', [{tag: 'doesntexist'}, {tag:'two'}], true],

        ['secondaryPreferred', undefined, true],
        ['secondaryPreferred', [{tag: 'one'}], false],
        ['secondaryPreferred', [{tag: 'two'}], true],

        // We don't have a way to alter ping times so we can't predict where an
        // untagged 'nearest' command should go, hence only test with tags.
        ['nearest', [{tag: 'one'}], false],
        ['nearest', [{tag: 'two'}], true]

    ].forEach(function(args) {
        var mode = args[0], tagSets = args[1], secExpected = args[2];

        var testDB = conn.getDB('test');
        conn.setSlaveOk(false); // purely rely on readPref
        jsTest.log('Testing mode: ' + mode + ', tag sets: ' + tojson(tagSets));

        var explainableQuery = testDB.user.explain().find();
        explainableQuery.readPref(mode, tagSets);
        var explain = explainableQuery.finish();
        assert.commandWorked(explain);

        var serverInfo;
        if (isMongos) {
            serverInfo = explain.queryPlanner.winningPlan.shards[0].serverInfo;
        }
        else {
            serverInfo = explain.serverInfo;
        }

        var explainDestConn = new Mongo(serverInfo.host + ':' + serverInfo.port);
        var isMaster = explainDestConn.getDB('admin').runCommand({ isMaster: 1 });

        if (secExpected) {
            assert(isMaster.secondary);
        }
        else {
            assert(isMaster.ismaster);
        }
    });
};

var st = new ShardingTest({ shards: { rs0: { nodes: NODE_COUNT }}});
st.stopBalancer();

ReplSetTest.awaitRSClientHosts(st.s, st.rs0.nodes);

// Tag primary with { dc: 'ny', tag: 'one' }, secondary with { dc: 'ny', tag: 'two' }
var primary = st.rs0.getPrimary();
var secondary = st.rs0.getSecondary();
var PRIMARY_TAG = { dc: 'ny', tag: 'one' };
var SECONDARY_TAG = { dc: 'ny', tag: 'two' };

var rsConfig = primary.getDB("local").system.replset.findOne();
jsTest.log('got rsconf ' + tojson(rsConfig));
rsConfig.members.forEach(function(member) {
    if (member.host == primary.host) {
        member.tags = PRIMARY_TAG;
    } else {
        member.tags = SECONDARY_TAG;
    }
});

rsConfig.version++;

jsTest.log('new rsconf ' + tojson(rsConfig));

try {
    primary.adminCommand({ replSetReconfig: rsConfig });
}
catch(e) {
    jsTest.log('replSetReconfig error: ' + e);
}

st.rs0.awaitSecondaryNodes();

// Force mongos to reconnect after our reconfig
assert.soon(function() {
    try {
        st.s.getDB('foo').runCommand({ create: 'foo' });
        return true;
    }
    catch (x) {
        // Intentionally caused an error that forces mongos's monitor to refresh.
        jsTest.log('Caught exception while doing dummy command: ' + tojson(x));
        return false;
    }
});

reconnect(primary);
reconnect(secondary);

rsConfig = primary.getDB("local").system.replset.findOne();
jsTest.log('got rsconf ' + tojson(rsConfig));

var replConn = new Mongo(st.rs0.getURL());

// Make sure replica set connection is ready
_awaitRSHostViaRSMonitor(primary.name, { ok: true, tags: PRIMARY_TAG }, st.rs0.name);
_awaitRSHostViaRSMonitor(secondary.name, { ok: true, tags: SECONDARY_TAG }, st.rs0.name);

testAllModes(replConn, false);

jsTest.log('Starting test for mongos connection');

testAllModes(st.s, true);

st.stop();