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Autoreleasing locks for node.js

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Description Build Status

Having locks in async world is not so straight-forward as it may look like. Everything can work fine, but when exception will be thrown in your app - locks may stay active until script's termination.

Here comes deadbolt to save all us:

var deadbolt = require('deadbolt');

deadbolt.lock('some-action-id', function (err, lock) {

  if (err) console.error(err); // 'some-action-id' is already running somewhere

  doAsyncActionThatProbablyThrows(function () {
    lock.release(function (err) {
      // Released lock if err === null
    });
  });

}).autorelease(function (err) {

  console.error('Execution stopped somewhere inside lock');
  console.error('Released lock automatically');
  console.error('Reason: ' + err);

});

Or just wrap callbacks without setting lock:

function asyncAction(callback) {
  callback = deadbolt.wrap(callback);
  doOtherAsyncActionThatMayForgotToCall(callback);
};

How does it work?

It's using v8's MakeWeak black magic. When lock becomes weak (not referenced in your program) - autorelease callback will be called.

Basically, if you forgot to call your callback - deadbolt will do it for you.

API

Full documentation is available here.

deadbolt.create

deadbolt.create('storage-type', { /* storage options */ });

Creates Deadbolt's instance, default storage type is memory (redis is available for multi-process locks).

Possible options for redis storage are:

{
  "host": "localhost",
  "port": 6379,
  "password": "redis password, if you have any",

  "ttl": 300, // time-to-live for locks (see EXPIRE command for redis)
  "prefix": "deadbolt" // all used keys will be prefixed
}

deadbolt.lock

// for global instance with memory storage
deadbolt.lock('lock-id', /* optional */ 'info', callback);

// For some manually created instance
Deadbolt#lock(...);

Creates lock, info will be shown in error passed to autorelease callback.

lock.release, lock.autorelease

deadbolt.lock(..., function(err, lock) {
  // Release lock manually
  lock.release(function(err) {
  });
}).autorelease(function(err) {
  // Lock was released automatically
});

Installation

If you're using npm:

npm install deadbolt

From source:

git clone git://github.com/indutny/deadbolt.git
cd deadbolt
./configure && make

LICENSE

(The MIT License)

Copyright (c) 2011 Fedor Indutny fedor@indutny.com

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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