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docs(transactions): adding examples for transactions
 Fixes NODE-1478
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‎test/functional/operation_promises_example_tests.js

+277
Original file line numberDiff line numberDiff line change
@@ -7240,4 +7240,281 @@ describe('Operation (Promises)', function() {
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// END
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}
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});
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describe('Transaction Examples', function() {
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before(function() {
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const configuration = this.configuration;
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const client = configuration.newClient(configuration.writeConcernMax());
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return client
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.connect()
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.then(() => client.db('hr').createCollection('employees'))
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.then(() => client.db('reporting').createCollection('events'));
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});
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// Start Transactions Intro Example 1
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it('should be able to run transactions example 1', {
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metadata: { requires: { topology: ['replicaset'], mongodb: '>=3.8.0' } },
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test: function() {
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const configuration = this.configuration;
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const client = configuration.newClient(configuration.writeConcernMax());
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// BEGIN
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function updateEmployeeInfo(client) {
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return client.withSession(session => {
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function commit() {
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return session.commitTransaction().catch(e => {
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if (e.errorLabels && e.errorLabels.indexOf('UnknownTransactionCommitResult') < 0) {
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// LINE console.log('Transaction aborted. Caught exception during transaction.');
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return commit();
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}
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// LINE console.log('Error during commit ...');
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throw e;
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});
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}
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const employeesCollection = client.db('hr').collection('employees');
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const eventsCollection = client.db('reporting').collection('events');
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session.startTransaction({
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readConcern: { level: 'snapshot' },
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writeConcern: { w: 'majority' }
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});
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return employeesCollection
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.updateOne({ employee: 3 }, { $set: { status: 'Inactive' } }, { session })
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.then(() => {
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return eventsCollection.insertOne(
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{
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employee: 3,
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status: { new: 'Inactive', old: 'Active' }
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},
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{ session }
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);
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})
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.catch(e => {
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// LINE console.log('caugh exception during transaction, aborting')
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return session.abortTransaction().then(() => Promise.reject(e));
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})
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.then(() => commit())
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.then(() => {
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// LINE console.log('Transaction committed');
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});
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});
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// END
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}
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client
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.connect()
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.then(() => updateEmployeeInfo(client))
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.then(() => client.close());
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}
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});
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// End Transactions Intro Example 1
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// Start Transactions Retry Example 1
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it('should be able to run transactions retry example 1', {
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metadata: { requires: { topology: ['replicaset'], mongodb: '>=3.8.0' } },
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test: function() {
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// BEGIN
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function runTransactionWithRetry(txnFunc, client, session) {
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return txnFunc(client, session).catch(error => {
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// LINE console.log('Transaction aborted. Caught exception during transaction.');
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// If transient error, retry the whole transaction
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if (error.errorLabels && error.errorLabels.indexOf('TransientTransactionError') < 0) {
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// LINE console.log('TransientTransactionError, retrying transaction ...');
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return runTransactionWithRetry(txnFunc, client, session);
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}
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throw error;
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});
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}
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// END
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function updateEmployeeInfo(client, session) {
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session.startTransaction({
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readConcern: { level: 'snapshot' },
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writeConcern: { w: 'majority' }
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});
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const employeesCollection = client.db('hr').collection('employees');
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const eventsCollection = client.db('reporting').collection('events');
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return employeesCollection
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.updateOne({ employee: 3 }, { $set: { status: 'Inactive' } }, { session })
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.then(() => {
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return eventsCollection.insertOne(
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{
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employee: 3,
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status: { new: 'Inactive', old: 'Active' }
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},
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{ session }
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);
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})
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.then(() => session.commitTransaction())
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.catch(e => {
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return session.abortTransaction().then(() => Promise.reject(e));
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});
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}
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const configuration = this.configuration;
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const client = configuration.newClient(configuration.writeConcernMax());
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return client
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.connect()
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.then(() =>
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client.withSession(session =>
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runTransactionWithRetry(updateEmployeeInfo, client, session)
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)
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)
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.then(() => client.close());
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}
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});
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// End Transactions Retry Example 1
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// Start Transactions Retry Example 2
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it('should be able to run transactions retry example 2', {
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metadata: { requires: { topology: ['replicaset'], mongodb: '>=3.8.0' } },
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test: function() {
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// BEGIN
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function commitWithRetry(session) {
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return (
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session
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.commitTransaction()
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// LINE .then(() => console.log('Transaction committed.'))
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.catch(error => {
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if (
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error.errorLabels &&
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error.errorLabels.indexOf('UnknownTransactionCommitResult') < 0
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) {
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// LINE console.log('UnknownTransactionCommitResult, retrying commit operation ...');
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return commitWithRetry(session);
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}
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// LINE console.log('Error during commit ...');
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throw error;
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})
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);
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}
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// END
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function updateEmployeeInfo(client, session) {
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session.startTransaction({
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readConcern: { level: 'snapshot' },
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writeConcern: { w: 'majority' }
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});
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const employeesCollection = client.db('hr').collection('employees');
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const eventsCollection = client.db('reporting').collection('events');
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return employeesCollection
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.updateOne({ employee: 3 }, { $set: { status: 'Inactive' } }, { session })
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.then(() => {
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return eventsCollection.insertOne(
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{
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employee: 3,
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status: { new: 'Inactive', old: 'Active' }
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},
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{ session }
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);
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})
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.then(() => commitWithRetry(session))
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.catch(e => {
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return session.abortTransaction().then(() => Promise.reject(e));
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});
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}
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const configuration = this.configuration;
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const client = configuration.newClient(configuration.writeConcernMax());
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return client
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.connect()
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.then(() => client.withSession(session => updateEmployeeInfo(client, session)))
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.then(() => client.close());
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}
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});
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// End Transactions Retry Example 2
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// Start Transactions Retry Example 3
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it('should be able to run transactions retry example 3', {
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metadata: { requires: { topology: ['replicaset'], mongodb: '>=3.8.0' } },
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test: function() {
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const configuration = this.configuration;
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const client = configuration.newClient(configuration.writeConcernMax());
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// BEGIN
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function commitWithRetry(session) {
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return (
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session
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.commitTransaction()
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// LINE .then(() => console.log('Transaction committed.'))
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.catch(error => {
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if (
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error.errorLabels &&
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error.errorLabels.indexOf('UnknownTransactionCommitResult') < 0
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) {
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// LINE console.log('UnknownTransactionCommitResult, retrying commit operation ...');
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return commitWithRetry(session);
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}
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// LINE console.log('Error during commit ...');
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throw error;
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})
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);
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}
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function runTransactionWithRetry(txnFunc, client, session) {
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return txnFunc(client, session).catch(error => {
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// LINE console.log('Transaction aborted. Caught exception during transaction.');
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// If transient error, retry the whole transaction
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if (error.errorLabels && error.errorLabels.indexOf('TransientTransactionError') < 0) {
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// LINE console.log('TransientTransactionError, retrying transaction ...');
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return runTransactionWithRetry(txnFunc, client, session);
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}
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throw error;
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});
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}
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function updateEmployeeInfo(client, session) {
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const employeesCollection = client.db('hr').collection('employees');
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const eventsCollection = client.db('reporting').collection('events');
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session.startTransaction({
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readConcern: { level: 'snapshot' },
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writeConcern: { w: 'majority' }
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});
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return employeesCollection
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.updateOne({ employee: 3 }, { $set: { status: 'Inactive' } }, { session })
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.then(() => {
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return eventsCollection.insertOne(
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{
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employee: 3,
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status: { new: 'Inactive', old: 'Active' }
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},
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{ session }
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);
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})
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.catch(e => {
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// LINE console.log('caugh exception during transaction, aborting')
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return session.abortTransaction().then(() => Promise.reject(e));
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})
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.then(() => commitWithRetry(session));
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}
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// LINE const { MongoClient } = require('mongodb'),
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// LINE const client = new MongoClient('myRepl/mongodb0.example.net:27017,mongodb1.example.net:27017,mongodb2.example.net:27017');
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return client
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.connect()
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.then(() =>
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client.withSession(session =>
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runTransactionWithRetry(updateEmployeeInfo, client, session)
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)
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)
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.then(() => client.close());
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// END
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}
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});
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// End Transactions Retry Example 3
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});
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});

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