coderanger / etcd-chef

etcd/chef integration PoC spike

Etcd/Chef integration

Etcd is a distributed key/value store, designed for service discovery and configuration alongside OS containers. For services and tools that don't directly support etcd, etcd-chef provides a way to write out configuration files and reload processes using the standard Chef DSL.

Running etcd-chef

etcd-chef takes most of the same options as chef-solo with a few exceptions. --interval will only have an effect on failed runs, as normal runs wait on etcd changes (see below for more information). Beyond that, use etcd-chef just as you would chef-solo:

$ etcd-chef -c config.rb

Accessing etcd values

Within your Chef recipes, you can use etcd in a similar way as you would normally use node to access attributes:

template '/etc/...' do
  variables secret_key: etcd['myapp']['secret_key']
end

Synchronized with etcd

etcd-chef automatically waits for a change in etcd and runs a converge cycle. This means that as soon as the cluster propagates a change, all etcd-chef daemons will activate. You may wish to set a --splay time if your recipe code involves non-local or contended resources.

Configuration

By default an etcd instance on localhost will be used. You can customize this either via --etcd-host and --etcd-port command line options, or etcd_host and etcd_port in your configuration file.