Use the Consul key-value store in Puppet code

This provides a simple way to set and get values from Consul's key-value store. A simple example:

$myobject = { 'some' => 'data' }
consulkv::set_json('consul-app.example.com', 'example/object', $myobject)

notice(consulkv::get_json('consul-app.example.com', 'example/object'))

This module also allows you to get the nodes associated with a service from Consul like so:

# get nodes providing the Consul service
$data = consulkv::get_service_nodes('consul-app.example.com', 'consul')

# Print the node name and IP of each node
$data.each |$item| {
  notice("${item['Node']} at ${item['Address']}")
}

# Print the entire JSON object returned from the API
# This is useful for seeing what properties are returned (such as 'Node' and 'Address')
notice($data.to_json_pretty)

Set up

All functions take a host as their first parameter. That host must be a Consul server that uses the Puppet CA for its SSL cert.

The functions authenticate themselves with the compiler's Puppet cert.

Reference

consulkv::get($host, $key)

consulkv::get('consul-app.example.com', 'key/path1') == 'rawdata'

This returns the raw value of a given key as a string. If the key doesn't exist, it returns undef.

consulkv::get_json($host, $key)

consulkv::get_json('consul-app.example.com', 'key/path2') == { 'my' => 'data' }

This parses value of a given key as JSON. If the key doesn't exist, it returns undef. If it can't parse the returned value, it will fail.

consulkv::set($host, $key, $string)

consulkv::set('consul-app.example.com', 'key/path1', 'rawdata')

This sets the value of a key to the passed string.

consulkv::set('consul-app.example.com', 'key/path1', undef)

If undef is passed instead of a string, the key is deleted.

consulkv::set_json($host, $key, $anything)

consulkv::set_json('consul-app.example.com', 'key/path2', { 'my' => 'data' })

This serializes the passed object as JSON, then stores it in the key.

consulkv::get_service_nodes($host, $service)

consulkv::get_service_nodes('consul-app.example.com', 'consul')

Returns the parsed JSON response as an array of hashes.

Note about SANs:

If your Consul servers' certificates have a SAN of consul.service.<your consul domain> you can simplify the examples above like so:

# assuming your Consul domain is consul.example.com
consulkv::get_service_nodes('consul.service.consul.example.com', 'some-service-name')

The advantage of this is you don't have to hard-code your Consul app servers' names in your Puppet code. This does require either allowing anonymous read access OR setting ACL's for where your Puppet queries run.