QA-112

read_pref_delay.js

// based from: https://gist.github.com/3fcf2a1c8583416c6ef9

var host = "replicaset.local";
var rsName = 'rs';

/**
 * @return the connection string of the bridged replica set.
 */
var getBridgedConnection = function (startDestPort, startBridgePort, delays) {
    var bridgeHosts = [];

    for (var i = 0; i < delays.length; ++i) {
        var destPort = startDestPort + i;
        var bridgePort = startBridgePort + i;
        stopMongod(bridgePort);
        startMongoProgram("mongobridge", "--port", bridgePort, "--dest", host + ":" + destPort, "--delay", delays[i]);
        bridgeHosts.push(host + ":" + bridgePort);
    }

    var url = rsName + '/' + bridgeHosts.join(',');
    return url;
};

var i, m, hit, reads;
var conn;

/* First test: no tagged read, mode "nearest", same latency for all. Reads
 * should be evenly distributed among all 5 members.
 */
reads = {};
var url = getBridgedConnection(37117, 37017, [0, 0, 0, 0, 0]);

jsTest.log('20 iterations, nearest, delay[0, 0, 0, 0, 0]');
for (i = 0; i < 20; ++i) {
    conn = new Mongo(url);
    c = conn.getCollection('test.foo');
    hit = c.find({x:1}).readPref("nearest").explain().server;
    reads[hit] = reads[hit] ? reads[hit] + 1 : 1;
}

print('result: ' + tojson(reads));

/* Second test: three members slow. Reads should be evenly distributed among the
 * fast two members.
 */
reads = {};
url = getBridgedConnection(37117, 37017, [0, 25, 25, 25, 0]);

sleep(60000); // wait for ReplicaSetMonitorWatcher to refresh
jsTest.log('20 iterations, nearest, delay[0, 25, 25, 25, 0]');
for (i = 0; i < 20; ++i) {
    conn = new Mongo(url);
    c = conn.getCollection('test.foo');

    hit = c.find({x:1}).readPref("nearest").explain().server;
    reads[hit] = reads[hit] ? reads[hit] + 1 : 1;
}

print('result: ' + tojson(reads));

/* Third test: primary slow with mode "primaryPreferred". Reads should target
 * only the primary.
 */
reads = {};
url = getBridgedConnection(37117, 37017, [25, 0, 0, 0, 0]);

sleep(60000); // wait for ReplicaSetMonitorWatcher to refresh
jsTest.log('20 iterations, priPref, delay[25, 0, 0, 0, 0]');
for (i = 0; i < 20; ++i) {
    conn = new Mongo(url);
    c = conn.getCollection('test.foo');

    hit = c.find({x:1}).readPref("primaryPreferred").explain().server;
    reads[hit] = reads[hit] ? reads[hit] + 1 : 1;
}

print('result: ' + tojson(reads));

/* Fourth test: all secondaries slow with mode "secondaryPreferred". Reads
 * should target only the secondaries.
 */
reads = {};
url = getBridgedConnection(37117, 37017, [0, 25, 25, 25, 25]);

sleep(60000); // wait for ReplicaSetMonitorWatcher to refresh
jsTest.log('20 iterations, secPref, delay[0, 25, 25, 25, 25]');
for (i = 0; i < 20; ++i) {
    conn = new Mongo(url);
    c = conn.getCollection('test.foo');

    hit = c.find({x:1}).readPref("secondaryPreferred").explain().server;
    reads[hit] = reads[hit] ? reads[hit] + 1 : 1;
}

print('result: ' + tojson(reads));

/* Fifth test: all but one secondary slow with mode "secondaryPreferred". Reads
 * should target only the fast secondary.
 */
reads = {};
url = getBridgedConnection(37117, 37017, [0, 25, 0, 25, 25]);

sleep(60000); // wait for ReplicaSetMonitorWatcher to refresh
jsTest.log('20 iterations, secPref, delay[0, 25, 0, 25, 25]');
for (i = 0; i < 20; ++i) {
    conn = new Mongo(url);
    c = conn.getCollection('test.foo');

    hit = c.find({x:1}).readPref("secondaryPreferred").explain().server;
    reads[hit] = reads[hit] ? reads[hit] + 1 : 1;
}

print('result: ' + tojson(reads));

/* Sixth test: all but one secondary slow with mode "secondaryPreferred".
 * Halfway during the queries, swap the fast secondary with another. Reads
 * should be evenly distributed between the fast secondaries.
 */
reads = {};
url = getBridgedConnection(37117, 37017, [0, 25, 25, 0, 25]);

sleep(60000); // wait for ReplicaSetMonitorWatcher to refresh
jsTest.log('10 iterations, secPref, delay[0, 25, 25, 0, 25]');
for (i = 0; i < 10; ++i) {
    conn = new Mongo(url);
    c = conn.getCollection('test.foo');

    hit = c.find({x:1}).readPref("secondaryPreferred").explain().server;
    reads[hit] = reads[hit] ? reads[hit] + 1 : 1;
}

url = getBridgedConnection(37117, 37017, [0, 25, 25, 25, 0]);

sleep(60000); // wait for ReplicaSetMonitorWatcher to refresh
jsTest.log('10 iterations, secPref, delay[0, 25, 25, 25, 0]');
for (i = 0; i < 10; ++i) {
    conn = new Mongo(url);
    c = conn.getCollection('test.foo');

    hit = c.find({x:1}).readPref("secondaryPreferred").explain().server;
    reads[hit] = reads[hit] ? reads[hit] + 1 : 1;
}

print('result: ' + tojson(reads));