Transaction

Transaction is a special class that allows you to add queries and commit them in one single batch, rolling back if any error occurs (on the DB or in your code inside the Transaction).

For more info please refer to The MongoDB manual

tl;dr - Usage

This is an example of using a transaction from Executor.

const { Mongo } = require('@jsmrcaga/executor');

// Get default DB

const db = Mongo.db();

// Create transaction

let transaction = db.transaction()

// Sadly binding is necessary, since the `this` arg will need

// to be reused inside

transaction.add(my_user.save.bind(my_user));

transaction.add(my_user_role.save.bind(my_user_role));

// We can also pass as many args aas we would normally pass to query

transaction.add(other_thing.update.bind(other_thing), {

name: 'New name!'

});

// And even options. But please read below to make sure everything works as

// expected

transaction.add(other_thing.update.bind(other_thing), {

name: 'New name!'

}, {

upsert: true

});

// Finally, we can commit the transaction

transaction.commit().then(() => 'yay!').catch(e => console.error(e));

Class Properties

db

A Database instance.

Transaction#constructor

Signature

new Transaction(db);

warning

You won't usually need to instanciate the Transaction object yourself. This is done for you using the db.transaction() method:

const { Mongo } = require('@jsmrcaga/executor');

const db = Mongo.db();

const newTransaction = db.transaction()

add

Signature

transaction.add(query, ...args)

This function takes two arguments. The first one is the query function you would like to run.

important

query MUST be a bound callable function. Look at the example below. Usually you will need to bind your function to keep this intact.

The rest (args) are all the arguments you would like to pass to your query function when running it.

warning

When running a transaction, the transaction method will run query by query, checking the length of each query (meaning the number of arguments it can take).

For Transaction the LAST argument is ALWAYS the options passed to the driver. Which means that if the last argument is provided, Transaction will try to merge it and add its session.

If there are any missing arugments between the provided list and the last one, Transaction will fill them with undefined.

Example

// Function with no extra arguments

transaction.add(my_user.save.bind(my_user));

// Function with all its arguments

transaction.add(other_thing.update.bind(other_thing), {

name: 'New name!'

}, {

upsert: true

});

commit

Signature

transaction.commit()

Commits the transaction using db.atomic().

This method will run every query function passed to it, and return a Promise.all of the lot.