Build Status

An interface to the Zookeeper cluster coordination server.

For a higher-level interface with a more convenient API and features such as locks, have a look at ZK.

Fork Safety!

As of 1.1.0, this library is fork-safe (which was not easy to accomplish). This means you can use it without worry in unicorn, resque, and whatever other fork-philic frameworks you sick little monkeys are using this week. The only rule is that after a fork(), you need to call #reopen on the client ASAP, because if you try to peform any other action, an exception will be raised. Other than that, there is no special action that is needed in the parent.

Big Plans for 1.0

The 1.0 release will feature a reorganization of the heirarchy. There will be a single top-level Zookeeper namespace (as opposed to the current layout, with 5-6 different top-level constants), and for the next several releases, there will be a backwards compatible require for users that still need to use the old names.


Copyright 2008 Phillip Pearson, and 2010 Twitter, Inc. Licensed under the MIT License. See the included LICENSE file.

Portions copyright 2008-2010 the Apache Software Foundation, licensed under the Apache 2 license, and used with permission.

Portions contributed to the open source community by HPDC, L.P.


sudo gem install zookeeper

rbenv is awesome

UPDATE: this appears to have been fixed by @eric in this patch. If you use rbenv, please report any issues, but I believe it should work now.

Let me start out by saying I prefer rvm, and that I really don't know a whole lot about linking on OS X. Or Linux. Any suggestions or constructive insults would be greatly appreciated if you have insight into what i'm doing wrong here.

So, it seems that ruby-build doesn't use --enable-shared by default. I'm told this is for speed.

If you run into problems with installing this gem (specifically with linking ex. Undefined symbols for architecture x86_64) and you're using rbenv, for now you need to ensure that your ruby was built with --enable-shared. I'm sorry for the inconvenience. (no, really)

~ $ CONFIGURE_OPTS='--enable-shared --disable-install-doc' rbenv install 1.9.3-p194

A note for REE users

The zookeeper client is required to send a heartbeat packet every N seconds to the server. If it misses its deadline 3 times in a row, the session will be lost. The way the client is implemented in versions >= 1.2, a ruby thread acts as the event thread (this was necessary to provide a fork-safe client with a parent process that is able to preserve state). Some users have reported issues where under load in "massive codebases," they have problems where calls will time out. Given the nature of the thread scheduler in 1.8, one should be careful if upgrading from 0.4.4 to >= 1.2.


Connect to a server:

require 'rubygems'
require 'zookeeper'
z = Zookeeper.new("localhost:2181")
z.get_children(:path => "/")


The following methods are initially supported:

  • get
  • set
  • get_children
  • stat
  • create
  • delete
  • get_acl
  • set_acl

All support async callbacks. get, get_children and stat support both watchers and callbacks.

Calls take a dictionary of parameters. With the exception of set_acl, the only required parameter is :path. Each call returns a dictionary with at minimum two keys :req_id and :rc.

A Bit about this repository

Twitter's open source office was kind enough to transfer this repository to facilitate development and administration of this repository. The zookeeper gem's last three releases were recorded in branches v0.4.2, v0.4.3 and v0.4.4. Releases of the slyphon-zookeeper gem were cut off of the fork, and unfortunately (due to an oversight on my part) were tagged with unrelated versions. Those were tagged with names release/0.9.2.

The plan is to keep the slyphon-zookeeper tags, and to tag the zookeeper releases twitter/release/0.4.x.

Further work will be carried out on this repository. The 0.9.3 release of the zookeeper gem will be released under the 'zookeeper' name, and will bring the two divergent (conceptual) branches of development together.