mongodb/jstests/replsets/inmemory_preserves_active_txns.js

/**
 * When a primary's oplog size exceeds the configured maximum, it must truncate the oplog only up to
 * the oldest active transaction timestamp at the time of the last stable checkpoint. The first
 * oplog entry that belongs to an active transaction is preserved, and all entries after it. A
 * secondary with the inMemory storage engine must treat its own oplog the same.
 *
 * This tests the oldestActiveTransactionTimestamp, which is calculated from the "startOpTime"
 * field of documents in the config.transactions collection.
 *
 * @tags: [uses_transactions, uses_prepare_transaction]
 */

(function() {
"use strict";
load("jstests/core/txns/libs/prepare_helpers.js");
load("jstests/libs/storage_helpers.js");  // getOldestRequiredTimestampForCrashRecovery()

// If the test runner passed --storageEngine=inMemory then we know inMemory is compiled into the
// server. We'll actually use both inMemory and wiredTiger storage engines.
const storageEngine = jsTest.options().storageEngine;
if (storageEngine !== 'inMemory') {
    jsTestLog(`Skip test: storageEngine == "${storageEngine}", not "inMemory"`);
    return;
}

// A new replica set for both the commit and abort tests to ensure the same clean state.
function doTest(commitOrAbort) {
    const replSet = new ReplSetTest({
        // Oplog can be truncated each "sync" cycle. Increase its frequency to once per second.
        nodeOptions: {syncdelay: 1, setParameter: {logComponentVerbosity: tojson({storage: 1})}},
        nodes: [
            {storageEngine: "wiredTiger"},
            // inMemory node must not be a voter, otherwise lastCommitted never advances
            {storageEngine: "inMemory", rsConfig: {priority: 0, votes: 0}},
        ],
        waitForKeys: false
    });

    replSet.startSet(PrepareHelpers.replSetStartSetOptions);
    replSet.initiateWithAnyNodeAsPrimary(
        null, "replSetInitiate", {doNotWaitForStableRecoveryTimestamp: true});

    const primary = replSet.getPrimary();
    const secondary = replSet.getSecondary();
    const primaryOplog = primary.getDB("local").oplog.rs;
    assert.lte(primaryOplog.dataSize(), PrepareHelpers.oplogSizeBytes);
    const secondaryOplog = secondary.getDB("local").oplog.rs;
    assert.lte(secondaryOplog.dataSize(), PrepareHelpers.oplogSizeBytes);

    const coll = primary.getDB("test").test;
    assert.commandWorked(coll.insert({}));

    jsTestLog("Prepare a transaction");

    const session = primary.startSession();
    session.startTransaction();
    assert.commandWorked(session.getDatabase("test").test.insert({myTransaction: 1}));
    const prepareTimestamp = PrepareHelpers.prepareTransaction(session);

    const oldestRequiredTimestampForCrashRecovery =
        getOldestRequiredTimestampForCrashRecovery(primary.getDB("test"));
    assert.lte(oldestRequiredTimestampForCrashRecovery, prepareTimestamp);

    jsTestLog("Get transaction entry from config.transactions");

    const txnEntry = primary.getDB("config").transactions.findOne();
    // The prepare oplog entry may or may not be the first oplog entry depending on packing.
    assert.lte(txnEntry.startOpTime.ts, prepareTimestamp, tojson(txnEntry));

    assert.soonNoExcept(() => {
        const secondaryTxnEntry = secondary.getDB("config").transactions.findOne();
        assert(secondaryTxnEntry);
        assert.eq(secondaryTxnEntry, txnEntry, tojson(secondaryTxnEntry));
        return true;
    });

    jsTestLog("Find prepare oplog entry");

    const oplogEntry = PrepareHelpers.findPrepareEntry(primaryOplog);
    assert.eq(oplogEntry.ts, prepareTimestamp, tojson(oplogEntry));
    // Must already be written on secondary, since the config.transactions entry is.
    const secondaryOplogEntry = PrepareHelpers.findPrepareEntry(secondaryOplog);
    assert.eq(secondaryOplogEntry.ts, prepareTimestamp, tojson(secondaryOplogEntry));

    jsTestLog("Insert documents until oplog exceeds oplogSize");

    // Oplog with prepared txn grows indefinitely - let it reach twice its supposed max size.
    PrepareHelpers.growOplogPastMaxSize(replSet);

    jsTestLog(`Oplog dataSize = ${primaryOplog.dataSize()}, check the prepare entry still exists`);

    assert.eq(oplogEntry, PrepareHelpers.findPrepareEntry(primaryOplog));
    assert.soon(() => {
        return secondaryOplog.dataSize() > PrepareHelpers.oplogSizeBytes;
    });
    assert.eq(oplogEntry, PrepareHelpers.findPrepareEntry(secondaryOplog));

    if (commitOrAbort === "commit") {
        jsTestLog("Commit prepared transaction and wait for oplog to shrink to max oplogSize");
        PrepareHelpers.commitTransaction(session, prepareTimestamp);
    } else if (commitOrAbort === "abort") {
        jsTestLog("Abort prepared transaction and wait for oplog to shrink to max oplogSize");
        assert.commandWorked(session.abortTransaction_forTesting());
    } else {
        throw new Error(`Unrecognized value for commitOrAbort: ${commitOrAbort}`);
    }

    PrepareHelpers.awaitOplogTruncation(replSet);

    replSet.stopSet();
}

doTest("commit");
doTest("abort");
})();