atomic

atomic

Atomic operations

Introduction

atomic lets you perform atomic operations based on keys. Additional tasks that try to access the same key get queued up and executed when the previous task calls done() to indicate it has finished its operation. It's useful when you want to perform a multiple I/O calls on databases and don't want anything else messing with your values in-between calls.

Installation

npm install atomic

Example

var atomic = require('atomic')()

var o = {} // here's our db

for (var i = 1; i <= 100; i++) {
  // create an atomic operation on key 'foo'
  atomic('foo', function (done, key, i) {
    setTimeout(function () {
      o[key] = i // store i in o[key]
      done() // done with this task, "unlock" key
             // and move to the next task in queue
    }, Math.floor(Math.random() * 50)) // sometime in the future
  }, i) // pass i to the arguments (closure)
}

atomic('foo', function (done, key) {
  console.log(o[key])
  done()
})

Usage

atomic(key, callback(done, key, arg1, arg2, ...) [, arg1, arg2, ...])

This creates an atomic operation on key. The callback is called when the key is free (other tasks have finished working on it) and you must call done() when you're finished your operations. For convenience, the key name and extra arguments are passed to the callback for your function to use.