Flock of Chefs

Flock of Chefs provides inter-node communication primatives to Chef instances.

Important note

This is highly experimental. It is not recommended near any environment where stability is an even remote priority. Currently this is a proof of concept to show that it can work and to get feedback on some use cases it can solve and how it can be made better.

How does it work

Flock of Chefs uses DCell to provide inter-node communications. It uses Celluloid actors to provide APIs with with remote nodes can interact. It also persists resources allowing for out of band action notifications.

Wait, what?

Yep, resources are persisted after the convergence has completed. This allows resources to be defined during the Chef run that subscribe to remote resouces. Since remote convergence may not be occurring in a timely manner, we want to allow the local convergence to continue on, allowing the resources with remote subscriptions to run when they are notified.

What's the API look like?

Currently the :flock_api is considered the public API provided via Flock. A :resource_manager actor exists, and can happily be used, but be warned it is highly prone to change as it is used internally for remote notifications and subscriptions.

Methods provided from the :flock_api

run_chef - Triggers a chef run on the node
active - Returns if chef is currently running on the node

Example of triggering a Chef client run:

FlockOfChefs['bender0'][:flock_api].run_chef

Usage

Remote notifications

# On node bender0
file '/tmp/fubar' do
  action :create
  content 'foobar'
  remote_notifies :run, 'execute[kill all humans]', :node => 'bender1'
end

When the node bender0 converges, if the file[/tmp/fubar] resource runs, it will trigger a remote notification. The remote notification will send the run action to the the execute[kill all humans] resource on the bender1 node.

Remote Subscriptions

# On node bender1
file '/tmp/fubar' do
  action :nothing
  content 'foobar'
  remote_subscribes :create, 'execute[kill all humans]', :node => 'bender0'
end

Wait for desired state

file '/tmp/fubar' do
  action :create
  content 'foobar'
  wait_until do
    FlockOfChefs['bender0'][:flock_api].active
  end
end

Wait while specific state exists

file '/tmp/fubar' do
  action :create
  content 'foobar'
  wait_while do
    FlockOfChefs['bender0'][:flock_api].active
  end
end

Library Info

Repository: https://github.com/chrisroberts/flock_of_chefs
Cookbook Repository: https://github.com/chrisrobrts/cookbook-flock_of_chefs

flock_of_chefs

Runtime