path: root/jstests/sharding/change_stream_transaction_sharded.js

// Confirms that change streams only see committed operations for sharded transactions.
// @tags: [
//   requires_sharding,
//   uses_change_streams,
//   uses_multi_shard_transaction,
//   uses_transactions,
// ]
(function() {
"use strict";

const dbName = "test";
const collName = "change_stream_transaction_sharded";
const namespace = dbName + "." + collName;

const st = new ShardingTest({
    shards: 2,
    rs: {nodes: 1, setParameter: {writePeriodicNoops: true, periodicNoopIntervalSecs: 1}}
});

const mongosConn = st.s;
assert.commandWorked(mongosConn.getDB(dbName).getCollection(collName).createIndex({shard: 1}));
st.ensurePrimaryShard(dbName, st.shard0.shardName);
// Shard the test collection and split it into two chunks: one that contains all {shard: 1}
// documents and one that contains all {shard: 2} documents.
st.shardColl(collName,
             {shard: 1} /* shard key */,
             {shard: 2} /* split at */,
             {shard: 2} /* move the chunk containing {shard: 2} to its own shard */,
             dbName,
             true);
// Seed each chunk with an initial document.
assert.commandWorked(mongosConn.getDB(dbName).getCollection(collName).insert(
    {shard: 1}, {writeConcern: {w: "majority"}}));
assert.commandWorked(mongosConn.getDB(dbName).getCollection(collName).insert(
    {shard: 2}, {writeConcern: {w: "majority"}}));

const db = mongosConn.getDB(dbName);
const coll = db.getCollection(collName);
let changeListShard1 = [], changeListShard2 = [];

//
// Start transaction 1.
//
const session1 = db.getMongo().startSession({causalConsistency: true});
const sessionDb1 = session1.getDatabase(dbName);
const sessionColl1 = sessionDb1[collName];
session1.startTransaction({readConcern: {level: "majority"}});

//
// Start transaction 2.
//
const session2 = db.getMongo().startSession({causalConsistency: true});
const sessionDb2 = session2.getDatabase(dbName);
const sessionColl2 = sessionDb2[collName];
session2.startTransaction({readConcern: {level: "majority"}});

/**
 * Asserts that there are no changes waiting on the change stream cursor.
 */
function assertNoChanges(cursor) {
    assert(!cursor.hasNext(), () => {
        return "Unexpected change set: " + tojson(cursor.toArray());
    });
}

//
// Perform writes both in and outside of transactions and confirm that the changes expected are
// returned by the change stream.
//
(function() {
/**
 * Asserts that the expected changes are found on the change stream cursor. Pushes the
 * corresponding change stream document (with resume token) to an array. When expected
 * changes are provided for both shards, we must assume that either shard's changes could
 * come first or that they are interleaved via applyOps index. This is because a cross shard
 * transaction may commit at a different cluster time on each shard, which impacts the
 * ordering of the change stream.
 */
function assertWritesVisibleWithCapture(cursor,
                                        expectedChangesShard1,
                                        expectedChangesShard2,
                                        changeCaptureListShard1,
                                        changeCaptureListShard2) {
    function assertChangeEqualWithCapture(changeDoc, expectedChange, changeCaptureList) {
        assert.eq(expectedChange.operationType, changeDoc.operationType);
        assert.eq(expectedChange._id, changeDoc.documentKey._id);
        changeCaptureList.push(changeDoc);
    }

    while (expectedChangesShard1.length || expectedChangesShard2.length) {
        assert.soon(() => cursor.hasNext());
        const changeDoc = cursor.next();

        if (changeDoc.documentKey.shard === 1) {
            assert(expectedChangesShard1.length);
            assertChangeEqualWithCapture(
                changeDoc, expectedChangesShard1[0], changeCaptureListShard1);
            expectedChangesShard1.shift();
        } else {
            assert(changeDoc.documentKey.shard === 2);
            assert(expectedChangesShard2.length);
            assertChangeEqualWithCapture(
                changeDoc, expectedChangesShard2[0], changeCaptureListShard2);
            expectedChangesShard2.shift();
        }
    }

    assertNoChanges(cursor);
}

// Open a change stream on the test collection.
const changeStreamCursor = coll.watch();

// Insert a document and confirm that the change stream has it.
assert.commandWorked(coll.insert({shard: 1, _id: "no-txn-doc-1"}, {writeConcern: {w: "majority"}}));
assertWritesVisibleWithCapture(changeStreamCursor,
                               [{operationType: "insert", _id: "no-txn-doc-1"}],
                               [],
                               changeListShard1,
                               changeListShard2);

// Insert two documents under each transaction and confirm no change stream updates.
assert.commandWorked(
    sessionColl1.insert([{shard: 1, _id: "txn1-doc-1"}, {shard: 2, _id: "txn1-doc-2"}]));
assert.commandWorked(
    sessionColl2.insert([{shard: 1, _id: "txn2-doc-1"}, {shard: 2, _id: "txn2-doc-2"}]));
assertNoChanges(changeStreamCursor);

// Update one document under each transaction and confirm no change stream updates.
assert.commandWorked(sessionColl1.update({shard: 1, _id: "txn1-doc-1"}, {$set: {"updated": 1}}));
assert.commandWorked(sessionColl2.update({shard: 2, _id: "txn2-doc-2"}, {$set: {"updated": 1}}));
assertNoChanges(changeStreamCursor);

// Update and then remove second doc under each transaction.
assert.commandWorked(
    sessionColl1.update({shard: 2, _id: "txn1-doc-2"}, {$set: {"update-before-delete": 1}}));
assert.commandWorked(
    sessionColl2.update({shard: 1, _id: "txn2-doc-1"}, {$set: {"update-before-delete": 1}}));
assert.commandWorked(sessionColl1.remove({shard: 2, _id: "txn1-doc-2"}));
assert.commandWorked(sessionColl2.remove({shard: 1, _id: "txn2-doc-2"}));
assertNoChanges(changeStreamCursor);

// Perform a write outside of a transaction and confirm that the change stream sees only
// this write.
assert.commandWorked(coll.insert({shard: 2, _id: "no-txn-doc-2"}, {writeConcern: {w: "majority"}}));
assertWritesVisibleWithCapture(changeStreamCursor,
                               [],
                               [{operationType: "insert", _id: "no-txn-doc-2"}],
                               changeListShard1,
                               changeListShard2);
assertNoChanges(changeStreamCursor);

// Perform a write outside of the transaction.
assert.commandWorked(coll.insert({shard: 1, _id: "no-txn-doc-3"}, {writeConcern: {w: "majority"}}));

// Commit first transaction and confirm that the change stream sees the changes expected
// from each shard.
assert.commandWorked(session1.commitTransaction_forTesting());
assertWritesVisibleWithCapture(changeStreamCursor,
                               [
                                   {operationType: "insert", _id: "no-txn-doc-3"},
                                   {operationType: "insert", _id: "txn1-doc-1"},
                                   {operationType: "update", _id: "txn1-doc-1"}
                               ],
                               [
                                   {operationType: "insert", _id: "txn1-doc-2"},
                                   {operationType: "update", _id: "txn1-doc-2"},
                                   {operationType: "delete", _id: "txn1-doc-2"}
                               ],
                               changeListShard1,
                               changeListShard2);
assertNoChanges(changeStreamCursor);

// Perform a write outside of the transaction.
assert.commandWorked(coll.insert({shard: 2, _id: "no-txn-doc-4"}, {writeConcern: {w: "majority"}}));

// Abort second transaction and confirm that the change stream sees only the previous
// non-transaction write.
assert.commandWorked(session2.abortTransaction_forTesting());
assertWritesVisibleWithCapture(changeStreamCursor,
                               [],
                               [{operationType: "insert", _id: "no-txn-doc-4"}],
                               changeListShard1,
                               changeListShard2);
assertNoChanges(changeStreamCursor);
changeStreamCursor.close();
})();

//
// Open a change stream at each resume point captured for the previous writes. Confirm that the
// documents returned match what was returned for the initial change stream.
//
(function() {

/**
 * Iterates over a list of changes and returns the index of the change whose resume token is
 * higher than that of 'changeDoc'. It is expected that 'changeList' entries at this index
 * and beyond will be included in a change stream resumed at 'changeDoc._id'.
 */
function getPostTokenChangeIndex(changeDoc, changeList) {
    for (let i = 0; i < changeList.length; ++i) {
        if (changeDoc._id._data < changeList[i]._id._data) {
            return i;
        }
    }

    return changeList.length;
}

/**
 * Confirms that the change represented by 'changeDoc' exists in 'shardChangeList' at index
 * 'changeListIndex'.
 */
function shardHasDocumentAtChangeListIndex(changeDoc, shardChangeList, changeListIndex) {
    assert(changeListIndex < shardChangeList.length);

    const expectedChangeDoc = shardChangeList[changeListIndex];
    assert.eq(changeDoc, expectedChangeDoc);
    assert.eq(expectedChangeDoc.documentKey,
              changeDoc.documentKey,
              tojson(changeDoc) + ", " + tojson(expectedChangeDoc));
}

/**
 * Test that change stream returns the expected set of documuments when resumed from each
 * point captured by 'changeList'.
 */
function confirmResumeForChangeList(changeList, changeListShard1, changeListShard2) {
    for (let i = 0; i < changeList.length; ++i) {
        const resumeDoc = changeList[i];
        let indexShard1 = getPostTokenChangeIndex(resumeDoc, changeListShard1);
        let indexShard2 = getPostTokenChangeIndex(resumeDoc, changeListShard2);
        const resumeCursor = coll.watch([], {startAfter: resumeDoc._id});

        while ((indexShard1 + indexShard2) < (changeListShard1.length + changeListShard2.length)) {
            assert.soon(() => resumeCursor.hasNext());
            const changeDoc = resumeCursor.next();

            if (changeDoc.documentKey.shard === 1) {
                shardHasDocumentAtChangeListIndex(changeDoc, changeListShard1, indexShard1++);
            } else {
                assert(changeDoc.documentKey.shard === 2);
                shardHasDocumentAtChangeListIndex(changeDoc, changeListShard2, indexShard2++);
            }
        }

        assertNoChanges(resumeCursor);
        resumeCursor.close();
    }
}

// Confirm that the sequence of events returned by the stream is consistent when resuming
// from any point in the stream on either shard.
confirmResumeForChangeList(changeListShard1, changeListShard1, changeListShard2);
confirmResumeForChangeList(changeListShard2, changeListShard1, changeListShard2);
})();

st.stop();
})();