txn

Flexible transaction management. Learn more about it in our blog post.

You can find a nice demo here.

Install

$ npm install @cheapreats/txn --save

Quick Start

Before creating a transaction, you must first define all the operations that can be rolled back. For example you might do something like this:

const User = require('./models/User');

function createUser(username, password) {
    let user = null;
    return {
        execute: () => {
            user = new User({username, password});
            await user.save();
        },
        rollback: () => {
            await user.delete();
        },
        retryPolicy: {
            count: 3,
            delay: 1000,
        }
    }
}

Above definition will simply create an user upon execute, and delete the user when rolling back. Retry policy is set to retry maximum 3 times, with delay between being 1000ms.

Now you can define a transaction, a transaction is simply a generator function that yields operations. Here we assume you also have createIdentity, sendVerificationEmail, and chargeMembershipFee defined.

function* signup(username, password, email, creditCard) {
    yield createUser(username, password);
    yield createIdentity(username, password);
    const verificationCode = getVerificationCode(email);
    yield sendVerificationEmail(email);
    yield chargeMembershipFee(creditCard);
}

Now you have a transaction defined, you can run it by wrapping it with txn.

const {txn} = require('@cheapreats/txn');

txn(signup('jun.zheng', 'test', '[email protected]', {/** ... */}))
    .then(result => {
        console.log(result);
        // process result here.
    })

txn method will resolve to null if transaction failed, otherwise it will give you an array with the following contents:

[
    {
        output: {}, // Output value for ith operation
        tries: 10 // Number of times tried.
    },
    // ...
]

If a rollback failed, then an error will be raised, you must handle that accordingly, usually we send a critical alert to admins.

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