mongo/jstests/replsets/read_committed.js

// Test basic read committed functionality.
(function() {
"use strict";

// Set up a set and grab things for later.
var name = "read_committed";
var replTest = new ReplSetTest({name: name,
                                nodes: 3,
                                nodeOptions: {enableMajorityReadConcern: ''}});
var nodes = replTest.nodeList();

try {
    replTest.startSet();
} catch (e) {
    var conn = MongoRunner.runMongod();
    if (!conn.getDB('admin').serverStatus().storageEngine.supportsCommittedReads) {
        jsTest.log("skipping test since storage engine doesn't support committed reads");
        MongoRunner.stopMongod(conn);
        return;
    }
    throw e;
}

replTest.initiate({"_id": name,
                   "members": [
                       { "_id": 0, "host": nodes[0] },
                       { "_id": 1, "host": nodes[1], priority: 0 },
                       { "_id": 2, "host": nodes[2], arbiterOnly: true}]
                  });

// Get connections and collection.
var primary = replTest.getPrimary();
var secondary = replTest.liveNodes.slaves[0];
var secondaryId = replTest.getNodeId(secondary);
var db = primary.getDB(name);
var t = db[name];

function doDirtyRead() {
    var res = t.runCommand('find', {"readConcern": {"level": "local"}});
    assert.commandWorked(res);
    return new DBCommandCursor(db.getMongo(), res).toArray()[0].state;
}

function doCommittedRead() {
    var res = t.runCommand('find', {"readConcern": {"level": "majority"}});
    assert.commandWorked(res);
    return new DBCommandCursor(db.getMongo(), res).toArray()[0].state;
}

// Do a write, wait for it to replicate, and ensure it is visible.
assert.writeOK(t.save({_id: 1, state: 0}, {writeConcern: {w: "majority", wtimeout: 60*1000}}));
assert.eq(doDirtyRead(), 0);
assert.eq(doCommittedRead(), 0);

replTest.stop(secondaryId);

// Do a write and ensure it is only visible to dirty reads
assert.writeOK(t.save({_id: 1, state: 1}));
assert.eq(doDirtyRead(), 1);
assert.eq(doCommittedRead(), 0);

// Try the committed read again after sleeping to ensure it doesn't only work for queries
// immediately after the write.
sleep(1000);
assert.eq(doCommittedRead(), 0);

// Restart the node and ensure the committed view is updated.
replTest.restart(secondaryId);
db.getLastError("majority", 60 * 1000);
assert.eq(doDirtyRead(), 1);
assert.eq(doCommittedRead(), 1);


}());