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/**
* Test that transactions are executed speculatively. This means two transactions affecting
* the same document can run back to back without waiting for the first transaction to
* commit to a majority.
*
* @tags: [uses_transactions, requires_majority_read_concern]
*/
(function() {
"use strict";
load("jstests/libs/write_concern_util.js"); // For stopServerReplication
const dbName = "test";
const collName = "speculative_transaction";
const rst = new ReplSetTest({name: collName, nodes: [{}, {rsConfig: {priority: 0}}]});
rst.startSet();
rst.initiate();
const primary = rst.getPrimary();
const secondary = rst.getSecondary();
var testDB = primary.getDB(dbName);
const coll = testDB[collName];
// The default WC is majority and stopServerReplication will prevent satisfying any majority writes.
assert.commandWorked(primary.adminCommand(
{setDefaultRWConcern: 1, defaultWriteConcern: {w: 1}, writeConcern: {w: "majority"}}));
function runTest(sessionOptions) {
testDB.runCommand({drop: collName, writeConcern: {w: "majority"}});
// Do an initial write so we have something to update.
assert.commandWorked(coll.insert([{_id: 0}, {_id: 1}], {w: "majority"}));
rst.awaitLastOpCommitted();
// Stop replication on the secondary so the majority commit never moves forward.
stopServerReplication(secondary);
// Initiate a session on the primary.
const session = testDB.getMongo().startSession(sessionOptions);
const sessionDb = session.getDatabase(dbName);
const sessionColl = sessionDb.getCollection(collName);
// Start the first transaction. Do not use majority commit for this one.
jsTestLog("Starting first transaction");
session.startTransaction({readConcern: {level: "snapshot"}, writeConcern: {w: 1}});
assert.commandWorked(sessionColl.update({_id: 0}, {$set: {x: 1}}));
assert.commandWorked(session.commitTransaction_forTesting());
// The document should be updated on the local snapshot.
assert.eq(coll.findOne({_id: 0}), {_id: 0, x: 1});
// The document should not be updated in the majority snapshot.
assert.eq(coll.find({_id: 0}).readConcern("majority").next(), {_id: 0});
jsTestLog("Starting second transaction");
// Start a second transaction. Still do not use majority commit for this one.
session.startTransaction({readConcern: {level: "snapshot"}, writeConcern: {w: 1}});
// We should see the updated doc within the transaction as a result of speculative read
// concern.
assert.eq(sessionColl.findOne({_id: 0}), {_id: 0, x: 1});
// Update it again.
assert.commandWorked(sessionColl.update({_id: 0}, {$inc: {x: 1}}));
// Update a different document outside the transaction.
assert.commandWorked(coll.update({_id: 1}, {$set: {y: 1}}));
// Within the transaction, we should not see the out-of-transaction update.
assert.eq(sessionColl.findOne({_id: 1}), {_id: 1});
assert.commandWorked(session.commitTransaction_forTesting());
// The document should be updated on the local snapshot.
assert.eq(coll.findOne({_id: 0}), {_id: 0, x: 2});
// The document should not be updated in the majority snapshot.
assert.eq(coll.find({_id: 0}).readConcern("majority").next(), {_id: 0});
// Make sure write conflicts are caught with speculative transactions.
jsTestLog("Starting a conflicting transaction which will be auto-aborted");
session.startTransaction({readConcern: {level: "snapshot"}, writeConcern: {w: 1}});
// Read some data inside the transaction.
assert.eq(sessionColl.findOne({_id: 1}), {_id: 1, y: 1});
// Write it outside the transaction.
assert.commandWorked(coll.update({_id: 1}, {$inc: {x: 1}}));
// Can still read old data in transaction.
assert.eq(sessionColl.findOne({_id: 1}), {_id: 1, y: 1});
// But update fails
assert.commandFailedWithCode(sessionColl.update({_id: 1}, {$inc: {x: 1}}),
ErrorCodes.WriteConflict);
assert.commandFailedWithCode(session.abortTransaction_forTesting(),
ErrorCodes.NoSuchTransaction);
// Restart server replication to allow majority commit point to advance.
restartServerReplication(secondary);
jsTestLog("Starting final transaction (with majority commit)");
// Start a third transaction, with majority commit.
session.startTransaction({readConcern: {level: "snapshot"}, writeConcern: {w: "majority"}});
// We should see the updated doc within the transaction.
assert.eq(sessionColl.findOne({_id: 0}), {_id: 0, x: 2});
// Update it one more time.
assert.commandWorked(sessionColl.update({_id: 0}, {$inc: {x: 1}}));
assert.commandWorked(session.commitTransaction_forTesting());
// The document should be updated on the local snapshot.
assert.eq(coll.findOne({_id: 0}), {_id: 0, x: 3});
// The document should also be updated in the majority snapshot.
assert.eq(coll.find({_id: 0}).readConcern("majority").next(), {_id: 0, x: 3});
session.endSession();
}
runTest({causalConsistency: false});
runTest({causalConsistency: true});
rst.stopSet();
}());
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