Mongo-distributed-locks NPM

mongo-distributed-locks

Node.js distributed locking based on Mongodb.

Commands

# Add to project
$ npm i mongo-distributed-locks

Usage

const DLocks = require('mongo-distributed-locks');

async function takeFee({ userId, fee }) {
  let user = await User.findOne({ _id: userId });
  user.balance -= fee;
  return user.save();
}

function takeFeeWithLock(params) {
  return DLocks.exec({
    resource: 'createPayment',
    id: params.userId,
    fn: takeFee.bind(null, params)
  });
}

function doWork() {
  let userId = 'userId';
  // current user balance is 60
  return Promise.all([
    takeFeeWithLock({ userId, fee: 10 }),
    takeFeeWithLock({ userId, fee: 25 })
  ]);
  // current user balance is 25
}

async function manageLockManually() {
  let userId = 'userId';
  let lock = await DLocks.lock({
    resource: 'user',
    id: userId
  });

  // current user balance is 60
  try {
    await takeFee({ userId, fee: 10 });
    await takeFee({ userId, fee: 25 });
    // current user balance is 25
  }
  finally {
    await DLocks.unlock(lock);
  }
}

API

static registerLoggerErrorFn(loggerErrorFn) Registers logger error function (DLocks can log a few error messages), if not provided console.error is used`.
- loggerErrorFn - logger error function. Example of usage: DLocks.registerLoggerErrorFn(logger.error.bind(logger));
static exec({ resource, id, fn }) Creates a DLocks instance and executes its exec method. Shortcut for let instance = new DLocks(params); instance.exec();.
- resource - operation: createPayment, or resource: user name.
- id - id of the locking resource.
- fn - function that does some operation on the locking resource.
static lock({ resource, id, fn }) Locks resource and returns lock object. This method can be helpful when you need to manage lock manually. Accepts the same parameters as static exec.
unlock(lock) Unlocks the previously locked resource.
- lock - previously generated lock object.