This Puppet module and plugin serves two functions. It provides a method for building Puppet manifests with dynamically-obtained ZooKeeper server lists. It also provides a method for configuring zk_watcher to monitor one or many services on a particular host, and register them with ZooKeeper.
The zkget function in thie module allows the Puppet Master server to ask
a ZooKeeper service for a list of servers at a particular path, and provides
that list in an array-form for your puppet manifests. This allwos you to
dynamically configure parts of your infrastructure without hard-coding server
hostnames or data.
In the Puppet manifest, get the list of servers. This retrieves a list of no less than 1 server, and no more than 10:
$servers = zkget('/services/memcache', 1, 10)
note: This function relies on servers being listed by their hostname and port,
which is how the zk_watcher daemon registers them.
The zkwatcher class installs the zk_watcher pip module, configures an
Upstart job to start up the service, and provides a definition that can be used
throughout your Puppet classes to register different services with Apache ZooKeeper
in a method that allows the above zkget function to be used.
Example usage:
zk::add { 'pgpool':
port => 5432,
cmd => 'service pgpool status',
path => "/services/production/pgpool",
refresh => '120';
}
Installation is simple... checkout this Git repository into a new module in your Puppet modules path, and create the configuration file ::
cd <your puppet path>/modules
git clone git@github.com:Nextdoor/puppet_zkwatcher.git zk_watcher