ynachiket/node-zk-ultralight

An ultralight locking library for ZooKeeper in nodejs

Ultralight ZK locking utility

Slimmer profile, low-calorie distributed locking library based on node-zookeeper-client

Why a new library?

• Mildly different, much smaller interface
• Fewer features (no master election)
• Incompatible locking strategy

Locking strategy

Like node-zookeeper-client, node-zk-ultralight's locking is based on the ZooKeeper lock recipe.

The key difference: the ZK lock recipe recommends negotiating for the lock under the requested lock node with child nodes like _locknode_/guid-lock-<sequence number>. However, ephemeral nodes may not have children, so applications with a large number of unique locks, especially a monotonically increasing number of locks (such as locking on a unique timestamp), pose a management problem. Locks created with node-zk-ultralight are ephemeral, and when no longer needed, they'll evaporate like the morning dew with the sunrise.

Usage

function someAsyncActionWithLocking(callback) {
  var cxn = zkultra.getCxn(settings.ZOOKEEPER_URLS);
  async.series([
    cxn.lock.bind(cxn, '/some/lock/i/need', process.title +'-'+ process.pid),
    someAsyncAction,
    cxn.unlock.bind(cxn, '/some/lock/i/need')
  ], callback);
};

Development

Building

$ git clone https://github.com/rackerlabs/node-zk-ultralight
$ cd node-zk-ultralight
$ npm install .
$ vagrant up
$ vagrant ssh
$ cd /vagrant
$ make

Tests

npm test

Lint

npm run-script lint

Coverage

npm run-script coverage

License

Library is distributed under the Apache license.