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.

Author

Alexander Mac

License

Licensed under the MIT license.