mongodb/jstests/replsets/secondary_reads_timestamp_visibility.js

/**
 * Tests that reads on a secondary during batch application only see changes that occur at the last
 * applied timestamp, which is advanced at the completion of each batch.
 *
 * This test uses a failpoint to block right before batch application finishes, while holding the
 * PBWM lock, and before advancing the last applied timestamp for readers.
 *
 */
(function() {
"use strict";

load('jstests/replsets/libs/secondary_reads_test.js');

const name = "secondaryReadsTimestampVisibility";
const collName = "testColl";
let secondaryReadsTest = new SecondaryReadsTest(name);
let replSet = secondaryReadsTest.getReplset();

let primaryDB = secondaryReadsTest.getPrimaryDB();
let secondaryDB = secondaryReadsTest.getSecondaryDB();

if (!primaryDB.serverStatus().storageEngine.supportsSnapshotReadConcern) {
    secondaryReadsTest.stop();
    return;
}
let primaryColl = primaryDB.getCollection(collName);

// Create a collection and an index. Insert some data.
primaryDB.runCommand({drop: collName});
assert.commandWorked(primaryDB.runCommand({create: collName}));
assert.commandWorked(primaryDB.runCommand(
    {createIndexes: collName, indexes: [{key: {y: 1}, name: "y_1", unique: true}]}));
for (let i = 0; i < 100; i++) {
    assert.commandWorked(primaryColl.insert({_id: i, x: 0, y: i + 1}));
}

replSet.awaitLastOpCommitted();
// This function includes a call to awaitReplication().
replSet.waitForAllIndexBuildsToFinish(primaryDB.getName(), collName);

// Sanity check.
assert.eq(secondaryDB.getCollection(collName).find({x: 0}).itcount(), 100);
assert.eq(secondaryDB.getCollection(collName).find({y: {$gte: 1, $lt: 101}}).itcount(), 100);

// Prevent a batch from completing on the secondary.
let pauseAwait = secondaryReadsTest.pauseSecondaryBatchApplication();

// Update x to 1 in each document with default writeConcern and make sure we see the correct
// data on the primary.
let updates = [];
for (let i = 0; i < 100; i++) {
    updates[i] = {q: {_id: i}, u: {x: 1, y: i}};
}
assert.commandWorked(primaryDB.runCommand({update: collName, updates: updates}));
assert.eq(primaryColl.find({x: 1}).itcount(), 100);
assert.eq(primaryColl.find({y: {$gte: 0, $lt: 100}}).itcount(), 100);

// Wait for the batch application to pause.
pauseAwait();

let levels = ["local", "available", "majority"];

if (!primaryDB.serverStatus().storageEngine.supportsCommittedReads) {
    levels = ["local", "available"];
}

// We should see the previous, un-replicated state on the secondary with every readconcern.
for (let i in levels) {
    print("Checking that no new updates are visible yet for readConcern: " + levels[i]);
    assert.eq(secondaryDB.getCollection(collName).find({x: 0}).readConcern(levels[i]).itcount(),
              100);
    assert.eq(secondaryDB.getCollection(collName).find({x: 1}).readConcern(levels[i]).itcount(), 0);
    assert.eq(secondaryDB.getCollection(collName)
                  .find({y: {$gte: 1, $lt: 101}})
                  .readConcern(levels[i])
                  .itcount(),
              100);
}

// Disable the failpoint and let the batch complete.
secondaryReadsTest.resumeSecondaryBatchApplication();

// Wait for the last op to appear in the majority committed snapshot on each node. This ensures
// that the op will be visible to a "majority" read.
replSet.awaitLastOpCommitted();

// Wait for the last op to be replicated to all nodes. This is needed because when majority read
// concern is disabled, awaitLastOpCommitted() just checks the node's knowledge of the majority
// commit point and does not ensure the node has applied the operations.
replSet.awaitReplication();

for (let i in levels) {
    print("Checking that new updates are visible for readConcern: " + levels[i]);
    // We should see the new state on the secondary with every readconcern.
    assert.eq(secondaryDB.getCollection(collName).find({x: 0}).readConcern(levels[i]).itcount(), 0);
    assert.eq(secondaryDB.getCollection(collName).find({x: 1}).readConcern(levels[i]).itcount(),
              100);
}
secondaryReadsTest.stop();
})();