Sets up replication based on node[:mongodb][:repl_set]

mongo_replication.rb

# Install the MongoDB gem
%w{ mongo bson_ext }.each do |mongo_gem|
  gem_install = gem_package mongo_gem do
    action :nothing
  end
  gem_install.run_action(:install)
end
Gem.clear_paths
require 'mongo'

# Get a list of other nodes in the same replica set
REPL_SET = node[:mongodb][:repl_set]
srch_trm = "mongodb_repl_set:#{REPL_SET}"
REPLICA_PEERS = search(:node, srch_trm).to_ary.collect {|host| host[:fqdn] }
REPLICA_PEERS.delete node[:fqdn]

ruby_block "Configure mongoDB replication" do
  block do
    Chef::Log.info "Configuring mongoDB replication..."
    require 'mongo'
    ##########################################################################
    # HELPER FUNCTIONS - should be in a library, but the 'mongo' require fails
    # Returns a BSON::OrderedHash from a hash (the keys are sorted)
    def self.ordered_hash_from_hash(regular_hash)
      ordered_hash = BSON::OrderedHash.new
      regular_hash.keys.sort.each do |key|
        ordered_hash[key.to_sym] = regular_hash[key]
      end
      ordered_hash
    end
    # returns the results of mongoDB's 'isMaster' shell command
    def is_master(connection)
      connection['admin'].command(ordered_hash_from_hash({:isMaster => true}))
    end
    ##########################################################################

    # STEP 1: wait for the server to become available, and get current status
    local_db = master_status = nil
    my_hostport = "#{node[:fqdn]}:#{node[:mongodb][:port]}"
    Chef::Log.info "Connecting to mongodb://localhost:#{node[:mongodb][:port]}..."
    while (local_db == nil) or (master_status == nil)
      begin
        local_db = Mongo::Connection.from_uri(
          "mongodb://localhost:#{node[:mongodb][:port]}",
          :logger => Chef::Log, :slave_ok => true)
        master_status = is_master(local_db)
      rescue Exception => e
        Chef::Log.warn "Error getting local master status: #{e.message}"
        localdb_files = Dir["#{node[:mongodb][:db_path]}/local*"].sort
        Chef::Log.info "Waiting for replication log to initilize? "+
           "(#{localdb_files.size} local.* files in #{node[:mongodb][:db_path]})"
        sleep 20
      end
    end

    # STEP 2: configure replication based on current status
    if master_status['ismaster'] or master_status['secondary']
      Chef::Log.info "Replication is already configured: #{master_status.inspect}"
    else
      Chef::Log.info "Replication is not configured (#{master_status['info']})"
      while is_master(local_db)['info'] =~ /local.system.replset .*EMPTYUNREACHABLE/
        Chef::Log.info "Replication is not configured: #{is_master(local_db)['info']}"
        sleep 10
      end
      if REPLICA_PEERS.empty?
        # Configure as the lone master
        Chef::Log.info "No other servers in replica set #{REPL_SET}; becoming master"
        Chef::Log.info "Setting master to: #{my_hostport}"
        local_db['admin'].command(ordered_hash_from_hash(
          :replSetInitiate => {
            "_id" => node[:mongodb][:repl_set],
               "members" => [{ "_id" => 0, "votes" => 2,
                 "host" => my_hostport }]
          }
        ))
      else
        # Configure as a slave
        Chef::Log.info "Found replica peers: #{REPLICA_PEERS.join ','}"
        replication_stared = false
        REPLICA_PEERS.each do |server|
          if not replication_stared
            Chef::Log.info "Retrieving replication settings from #{server}..."
            peer_db =  Mongo::Connection.from_uri(
              "mongodb://#{server}:#{node[:mongodb][:port]}",
              :logger => Chef::Log, :slave_ok => true)
            repl_settings = peer_db['local']["system.replset"].find_one
            Chef::Log.info "Replication settings for #{server}: "+
              repl_settings.inspect
            if is_master(peer_db)['ismaster']
              Chef::Log.info "Starting replication from master: #{server}..."
              active_peers = repl_settings['members'].collect {|m| m['host'] }
              if active_peers.include? my_hostport
                Chef::Log.error "Host #{my_hostport} already in replica set!"
              else
                repl_settings["version"] += 1   # increment config version
                max_id = repl_settings['members'].inject(0) do |max, peer|
                  peer['_id'] > max ? peer['_id'] : max
                end
                repl_settings['members'].push(
                  {'host' => my_hostport, '_id' => max_id+1})
                bson = ordered_hash_from_hash(:replSetReconfig => repl_settings)
                Chef::Log.info "Pushing replication settings: #{repl_settings.inspect}"
                peer_db['admin'].command(bson)
                replication_stared = true
              end
            end
          end
        end
      end
    end

    # STEP 3: wait for the local replication status to be OK
    while not (is_master(local_db)['ismaster'] or is_master(local_db)['secondary'])
      Chef::Log.info "Waiting for local replication (#{is_master(local_db)['info']})"
      sleep 10
    end
    Chef::Log.info("Local replication status: #{is_master(local_db).inspect}")
  end
end