mongo/jstests/sharding/read_pref.js

/**
 * Integration test for read preference and tagging. The more comprehensive unit test can be found
 * in dbtests/replica_set_monitor_test.cpp.
 */

// Checking UUID consistency involves talking to a shard node, which in this test is shutdown
TestData.skipCheckingUUIDsConsistentAcrossCluster = true;

(function() {
    'use strict';

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

    var PRI_TAG = {dc: 'ny'};
    var SEC_TAGS = [{dc: 'sf', s: "1"}, {dc: 'ma', s: "2"}, {dc: 'eu', s: "3"}, {dc: 'jp', s: "4"}];
    var NODES = SEC_TAGS.length + 1;

    var doTest = function(useDollarQuerySyntax) {
        var st =
            new ShardingTest({shards: {rs0: {nodes: NODES, oplogSize: 10, useHostName: true}}});
        var replTest = st.rs0;
        var primaryNode = replTest.getPrimary();

        // The $-prefixed query syntax is only legal for compatibility mode reads, not for the
        // find/getMore commands.
        if (useDollarQuerySyntax && st.s.getDB("test").getMongo().useReadCommands()) {
            st.stop();
            return;
        }

        var setupConf = function() {
            var replConf = primaryNode.getDB('local').system.replset.findOne();
            replConf.version = (replConf.version || 0) + 1;

            var secIdx = 0;
            for (var x = 0; x < NODES; x++) {
                var node = replConf.members[x];

                if (node.host == primaryNode.name) {
                    node.tags = PRI_TAG;
                } else {
                    node.tags = SEC_TAGS[secIdx++];
                    node.priority = 0;
                }
            }

            try {
                primaryNode.getDB('admin').runCommand({replSetReconfig: replConf});
            } catch (x) {
                jsTest.log('Exception expected because reconfiguring would close all conn, got ' +
                           x);
            }

            return replConf;
        };

        var checkTag = function(nodeToCheck, tag) {
            for (var idx = 0; idx < NODES; idx++) {
                var node = replConf.members[idx];

                if (node.host.toLowerCase() == nodeToCheck.toLowerCase()) {
                    jsTest.log('node[' + node.host + '], Tag: ' + tojson(node['tags']));
                    jsTest.log('tagToCheck: ' + tojson(tag));

                    var nodeTag = node['tags'];

                    for (var key in tag) {
                        assert.eq(tag[key], nodeTag[key]);
                    }

                    return;
                }
            }

            assert(false, 'node ' + nodeToCheck + ' not part of config!');
        };

        var replConf = setupConf();

        var conn = st.s;

        // Wait until the ReplicaSetMonitor refreshes its view and see the tags
        var replConfig = replTest.getReplSetConfigFromNode();
        replConfig.members.forEach(function(node) {
            var nodeConn = new Mongo(node.host);
            awaitRSClientHosts(conn, nodeConn, {ok: true, tags: node.tags}, replTest);
        });
        replTest.awaitReplication();

        jsTest.log('New rs config: ' + tojson(primaryNode.getDB('local').system.replset.findOne()));
        jsTest.log('connpool: ' + tojson(conn.getDB('admin').runCommand({connPoolStats: 1})));

        var coll = conn.getDB('test').user;

        assert.soon(function() {
            var res = coll.insert({x: 1}, {writeConcern: {w: NODES}});
            if (!res.hasWriteError()) {
                return true;
            }

            var err = res.getWriteError().errmsg;
            // Transient transport errors may be expected b/c of the replSetReconfig
            if (err.indexOf("transport error") == -1) {
                throw err;
            }
            return false;
        });

        var getExplain = function(readPrefMode, readPrefTags) {
            if (useDollarQuerySyntax) {
                var readPrefObj = {mode: readPrefMode};

                if (readPrefTags) {
                    readPrefObj.tags = readPrefTags;
                }

                return coll.find({$query: {}, $readPreference: readPrefObj, $explain: true})
                    .limit(-1)
                    .next();
            } else {
                return coll.find().readPref(readPrefMode, readPrefTags).explain("executionStats");
            }
        };

        var getExplainServer = function(explain) {
            assert.eq("SINGLE_SHARD", explain.queryPlanner.winningPlan.stage);
            var serverInfo = explain.queryPlanner.winningPlan.shards[0].serverInfo;
            return serverInfo.host.toLowerCase() + ":" + serverInfo.port.toString();
        };

        // Read pref should work without slaveOk
        var explain = getExplain("secondary");
        var explainServer = getExplainServer(explain);
        assert.neq(primaryNode.name, explainServer);

        conn.setSlaveOk();

        // It should also work with slaveOk
        explain = getExplain("secondary");
        explainServer = getExplainServer(explain);
        assert.neq(primaryNode.name, explainServer);

        // Check that $readPreference does not influence the actual query
        assert.eq(1, explain.executionStats.nReturned);

        explain = getExplain("secondaryPreferred", [{s: "2"}]);
        explainServer = getExplainServer(explain);
        checkTag(explainServer, {s: "2"});
        assert.eq(1, explain.executionStats.nReturned);

        // Cannot use tags with primaryOnly
        assert.throws(function() {
            getExplain("primary", [{s: "2"}]);
        });

        // Ok to use empty tags on primaryOnly
        explain = getExplain("primary", [{}]);
        explainServer = getExplainServer(explain);
        assert.eq(primaryNode.name, explainServer);

        explain = getExplain("primary", []);
        explainServer = getExplainServer(explain);
        assert.eq(primaryNode.name, explainServer);

        // Check that mongos will try the next tag if nothing matches the first
        explain = getExplain("secondary", [{z: "3"}, {dc: "jp"}]);
        explainServer = getExplainServer(explain);
        checkTag(explainServer, {dc: "jp"});
        assert.eq(1, explain.executionStats.nReturned);

        // Check that mongos will fallback to primary if none of tags given matches
        explain = getExplain("secondaryPreferred", [{z: "3"}, {dc: "ph"}]);
        explainServer = getExplainServer(explain);
        // Call getPrimary again since the primary could have changed after the restart.
        assert.eq(replTest.getPrimary().name, explainServer);
        assert.eq(1, explain.executionStats.nReturned);

        // Kill all members except one
        var stoppedNodes = [];
        for (var x = 0; x < NODES - 1; x++) {
            replTest.stop(x);
            stoppedNodes.push(replTest.nodes[x]);
        }

        // Wait for ReplicaSetMonitor to realize nodes are down
        awaitRSClientHosts(conn, stoppedNodes, {ok: false}, replTest.name);

        // Wait for the last node to be in steady state -> secondary (not recovering)
        var lastNode = replTest.nodes[NODES - 1];
        awaitRSClientHosts(conn, lastNode, {ok: true, secondary: true}, replTest.name);

        jsTest.log('connpool: ' + tojson(conn.getDB('admin').runCommand({connPoolStats: 1})));

        // Test to make sure that connection is ok, in prep for priOnly test
        explain = getExplain("nearest");
        explainServer = getExplainServer(explain);
        assert.eq(explainServer, replTest.nodes[NODES - 1].name);
        assert.eq(1, explain.executionStats.nReturned);

        // Should assert if request with priOnly but no primary
        assert.throws(function() {
            getExplain("primary");
        });

        st.stop();
    };

    doTest(false);
    doTest(true);
})();