rabbitmq.rb

# Use Zookeeper to add/remove from the cluster as required.
require 'zk'
zookeeper_node = search(:node, "role:zookeeper AND chef_environment:#{node.chef_environment}")[0]
listen_ip = zookeeper_node[:ipaddress]
zk = ZK.new("#{listen_ip}:2181")

# Cluster members reported by Zookeeper.
active_cluster_members = zk.children(node[:zk_watcher][:zk_node_path]).collect { |x| x.split(':')[0] }
# Cluster members reported by the node.
node_cluster_members = eval %x[rabbitmqctl cluster_status -q | grep running_nodes | grep -o "\[.*\]"]

# This node is in a cluster by itself, it needs to join
# one of the cluster nodes.
if node_cluster_members.length == 1
  bash "join_cluster" do
    user "root"
    code <<-EOH
    rabbitmqctl stop_app
    rabbitmqctl reset
    rabbitmqctl join_cluster #{active_cluster_members.to_set.first}
    rabbitmqctl start_app
    EOH
    returns [0,1,2,3]
  end
else
  # At last one node needs to add any missing nodes to the cluster. All nodes
  # can try, and we'll ignore those that fail because the node is already a member.
  nodes_to_add = active_cluster_members.to_set - node_cluster_members.to_set
  nodes_to_add.each do |new_node|
    bash "add_node_to_cluster" do
      user "root"
      code <<-EOH
      rabbitmqctl stop_app
      rabbitmqctl reset
      rabbitmqctl join_cluster #{new_node}
      rabbitmqctl start_app
      EOH
      returns [0,1,2,3]
    end
  end

  # At least one node needs to forget any stale nodes on behalf of the cluster.
  # All nodes can try, and we'll ignore those that fail because the node has left.
  nodes_to_remove = node_cluster_members.to_set - active_cluster_members.to_set
  nodes_to_remove.each do |dead_node|
    bash "remove_node_from_cluster" do
      user "root"
      code <<-EOH
      rabbitmqctl join_cluster forget_cluster_node #{dead_node}
      EOH
      returns [0,1,2,3]
    end
  end
end