mongo/jstests/replsets/fsync_lock_read_secondaries.js

/* @file : jstests/fsync_lock_read_secondaries.js
 * 
 * SERVER 4243 : If there is a pending write due to an fsync lock, all reads are blocked
 *
 * This test validates part of SERVER-4243 ticket. Allow reading on secondaries with fsyncLock
 * mode enabled. Previously oplog application would cause blocking.
 * The corresponding commit :
 * https://github.com/mongodb/mongo/commit/73aa870d129bd7d51de946b91c16cc056aaacbc7
 */

/*
 * 1) Create a replica set.
 * 2) Add some documents to master.
 * 3) Wait until the secondary nodes are in state "SECONDARY".
 * 4) Set slaveOk on secondary.
 * 5) Take the fsync lock on a secondary. This will stop replication.
 * 6) Insert some more documents to master.
 * 7) Expect to be able to read from the secondary; the count of documents should
 *    be equal to the number of documents added in step 2.
 * 8) Release the fsync lock. This will resume replication.
 * 9) Soon, the secondary should be applying the oplog again, which we should
 *    witness as an increase in the count of documents stored on the secondary.
 */
(function() {
"use strict";
// Load utility methods for replica set tests
load("jstests/replsets/rslib.js");

var replTest = new ReplSetTest({name: 'testSet', nodes: 2, oplogSize: 5});
// Start each mongod in the replica set. Returns a list of nodes
var nodes = replTest.startSet();
// This will wait for initiation
replTest.initiate();
var master = replTest.getPrimary();

var ret = master.getDB("admin").fsyncLock();
if (!ret.ok) {
    assert.commandFailedWithCode(ret, ErrorCodes.CommandNotSupported);
    jsTestLog("Storage Engine does not support fsyncLock, so bailing");
    return;
}
master.getDB("admin").fsyncUnlock();

var docNum = 100;
for(var i=0; i<docNum; i++) {
    master.getDB("foo").bar.save({a: i});
}
waitForAllMembers(master.getDB("foo"));
replTest.awaitReplication();

// Calling getPrimary also makes available the liveNodes structure, which looks like this:
// liveNodes = {master: masterNode, slaves: [slave1, slave2] }
var slaves = replTest.liveNodes.slaves;
slaves[0].setSlaveOk();

assert.commandWorked(slaves[0].getDB("admin").runCommand({fsync:1, lock: 1}));
var docNum = 1000;
for (var i=0; i<docNum; i++) {
    master.getDB("foo").bar.save({a: i});
}
// Issue a read query on the secondary while holding the fsync lock.
// This is what we are testing. Previously this would block. After the fix 
// this should work just fine.
var slave0count = slaves[0].getDB("foo").bar.count();
assert.eq(slave0count, 100, "Doc count in fsync lock wrong. Expected (=100), found " + slave0count);
assert(slaves[0].getDB("admin").fsyncUnlock().ok);

// The secondary should have equal or more documents than what it had before.
assert.soon(function() {
        return slaves[0].getDB("foo").bar.count() > 100
    }, "count of documents stored on the secondary did not increase");
replTest.stopSet();
}());