Class: MQRPC::Agent

Inherits:
Object
  • Object
show all
Defined in:
lib/mqrpc/agent.rb

Overview

TODO: document this class

Constant Summary collapse

MAXBUF = 
20
MAXMESSAGEWAIT = 
MAXBUF * 20

Class Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(config) ⇒ Agent

Returns a new instance of Agent.



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# File 'lib/mqrpc/agent.rb', line 56

def initialize(config)
  Thread::abort_on_exception = true
  @config = config
  @handler = self
  @id = UUID::generate
  @outbuffer = Hash.new { |h,k| h[k] = [] }
  @queues = Set.new
  @topics = Set.new
  @receive_queue = Queue.new
  @want_subscriptions = Queue.new

  # figure out how to really do this correctly, see also def self.pipeline
  if self.class.pipelines == nil
    self.class.pipelines = Hash.new
  end

  @slidingwindow = Hash.new do |h,k| 
    MQRPC::logger.debug "New sliding window for #{k}"
    h[k] = SizedThreadSafeHash.new(MAXMESSAGEWAIT) do |state|
      if self.class.pipelines[k]
        source = self.class.pipelines[k]
        MQRPC::logger.debug "Got sizedhash callback for #{k}: #{state}"
        case state
        when :blocked
          MQRPC::logger.info("Queue '#{k}' is full, unsubscribing from #{source}")
          unsubscribe(source)
        when :ready
          MQRPC::logger.info("Queue '#{k}' is ready, resubscribing to #{source}")
          subscribe(source)
        end
      end
    end
  end

  @mq = nil
  @message_operations = Hash.new

  @startup_mutex = Mutex.new
  @startup_condvar = ConditionVariable.new
  @amqp_ready = false

  start_amqp

  # Wait for our AMQP thread to get going. Mainly, it needs to set
  # @mq, so we'll block until it's available.
  @startup_mutex.synchronize do
    MQRPC::logger.debug "Waiting for @mq ..."
    @startup_condvar.wait(@startup_mutex) if !@amqp_ready
    MQRPC::logger.debug "Got it, continuing with #{self.class} init..."
  end

  start_receiver
end

Class Attribute Details

.message_handlers ⇒ Object

Returns the value of attribute message_handlers.



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# File 'lib/mqrpc/agent.rb', line 35

def message_handlers
  @message_handlers
end

.pipelines ⇒ Object

Returns the value of attribute pipelines.



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# File 'lib/mqrpc/agent.rb', line 36

def pipelines
  @pipelines
end

Class Method Details

.handle(messageclass, method) ⇒ Object

Subclasses use this to declare their support of any given message



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# File 'lib/mqrpc/agent.rb', line 41

def self.handle(messageclass, method)
  if self.message_handlers == nil
    self.message_handlers = Hash.new
  end
  self.message_handlers[messageclass] = method
end

.pipeline(source, destination) ⇒ Object 



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# File 'lib/mqrpc/agent.rb', line 48

def self.pipeline(source, destination)
  if self.pipelines == nil
    self.pipelines = Hash.new
  end

  self.pipelines[destination] = source
end

Instance Method Details

#can_receive?(message_class) ⇒ Boolean

run

Returns:

  • (Boolean) 


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# File 'lib/mqrpc/agent.rb', line 248

def can_receive?(message_class)
  if self.class.message_handlers == nil
    self.class.message_handlers = []
  end

  return self.class.message_handlers.include?(message_class)
end

#close ⇒ Object 



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# File 'lib/mqrpc/agent.rb', line 355

def close
  EM.stop_event_loop
end

#flushout(destination) ⇒ Object

def handle_subscriptions



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# File 'lib/mqrpc/agent.rb', line 303

def flushout(destination)
  msgs = @outbuffer[destination]
  return if msgs.length == 0
  data = msgs.to_json
  @mq.queue(destination, :durable => true).publish(data, :persistent => true)
  msgs.clear
end

#handle_message(hdr, msg_body) ⇒ Object

def subscribe_topic



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# File 'lib/mqrpc/agent.rb', line 179

def handle_message(hdr, msg_body)
  queue = hdr.routing_key

  # If we just unsubscribed from a queue, we may still have some
  # messages buffered, so reject the message.
  # Currently RabbitMQ doesn't support message rejection, so let's
  # ack the message then push it back into the queue, unmodified.
  if !@queues.include?(queue)
    MQRPC::logger.warn("Got message on queue #{queue} that we are not "\
                       "subscribed to; rejecting")
    hdr.ack
    @mq.queue(queue, :durable => true).publish(msg_body, :persistent => true)
    return
  end

  begin
    obj = JSON::load(msg_body)
  rescue JSON::ParserError
    MQRPC::logger.warn("Skipping non-JSON message: #{msg_body}")
    hdr.ack
    return
  end
  if !obj.is_a?(Array)
    obj = [obj]
  end

  obj.each do |item|
    message = Message.new_from_data(item)
    slidingwindow = @slidingwindow[queue]
    if message.respond_to?(:from_queue)
      slidingwindow = @slidingwindow[message.from_queue]
    end
    MQRPC::logger.debug "Got message #{message.class}##{message.id} on queue #{queue}"
    #MQRPC::logger.debug "Received message: #{message.inspect}"
    if (message.respond_to?(:in_reply_to) and 
        slidingwindow.include?(message.in_reply_to))
      MQRPC::logger.debug "Got response to #{message.in_reply_to}"
      slidingwindow.delete(message.in_reply_to)
    end

    # Check if we have a specific operation looking for this
    # message.
    if (message.respond_to?(:in_reply_to) and
        @message_operations.has_key?(message.in_reply_to))
      operation = @message_operations[message.in_reply_to]
      operation.call(message)
    elsif can_receive?(message.class)
      func = self.class.message_handlers[message.class]
      self.send(func, message) do |response|
        reply_destination = message.reply_to
        response.from_queue = queue
        sendmsg(reply_destination, response)
      end

      # TODO(sissel): We should allow the message handler to defer acking
      # if they want For instance, if we want to index things, but only
      # want to ack things once we actually flush to disk.
    else
      $stderr.puts "#{@handler.class.name} does not support #{message.class}"
    end 
  end
  hdr.ack
end

#handle_subscriptions ⇒ Object 



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# File 'lib/mqrpc/agent.rb', line 256

def handle_subscriptions
  Thread.current[:name] = "subscriptionhandler"
  while true do
    queuetype, name = @want_subscriptions.pop

    case queuetype
    when :queue
      if @queues.include?(name) 
        MQRPC::logger.info "Ignoring subscription request to queue "\
                           "#{name}, already subscribed."
        next
      end
      MQRPC::logger.info "Subscribing to queue #{name}"
      # Send a dummy message to queue #{name} so there's at least
      # one message to receive, and wake up our Operation.
      sendmsg(name, DummyMessage.new)
      exchange = @mq.topic(@config.mqexchange, :durable => true)
      mq_q = @mq.queue(name, :durable => true)
      mq_q.bind(exchange, :key => "*")
      op = Operation.new
      mq_q.subscribe(:ack => true) do |hdr, msg| 
        op.finished
        return if msg.is_a?(DummyMessage)
        queue = hdr.routing_key
        MQRPC::logger.info("received message on #{queue}")
        @receive_queue << [hdr, msg]
        MQRPC::logger.info("finished receiving message on #{queue}") 
        MQRPC::logger.info("msg: #{msg}")
        MQRPC::logger.info("#{queue} queue size: #{@receive_queue.length}") 
      end
      # Wait until we receive our first message (might be DummyMessage,
      # doesn't matter) -- this confirms we are subscribed. subscribe
      # is async...
      op.wait_until_finished
      @queues << name
    when :topic
      MQRPC::logger.info "Subscribing to topic #{name}"
      exchange = @mq.topic(@config.mqexchange, :durable => true)
      mq_q = @mq.queue("#{@id}-#{name}",
                       :exclusive => true,
                       :auto_delete => true).bind(exchange, :key => name)
      mq_q.subscribe { |hdr, msg| @receive_queue << [hdr, msg] }
      @topics << name
    end # case queuetype
  end # while true
end

#handler=(handler) ⇒ Object 



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# File 'lib/mqrpc/agent.rb', line 351

def handler=(handler)
  @handler = handler
end

#run ⇒ Object

def handle_message



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# File 'lib/mqrpc/agent.rb', line 243

def run
  Thread.current[:name] ||= "#{self.class.name}#run"
  @amqpthread.join
end

#sendmsg(destination, msg, &callback) ⇒ Object 



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# File 'lib/mqrpc/agent.rb', line 321

def sendmsg(destination, msg, &callback)
  if (msg.is_a?(RequestMessage) and msg.id == nil)
    msg.generate_id!
  end
  msg.timestamp = Time.now.to_f
  msg.reply_to = @id

  if msg.is_a?(RequestMessage)
    MQRPC::logger.debug "Tracking #{msg.class.name}##{msg.id} to #{destination}"
    @slidingwindow[destination][msg.id] = true
  end

  if msg.delayable
    @outbuffer[destination] << msg
    if @outbuffer[destination].length > MAXBUF
      flushout(destination)
    end
  else
    MQRPC::logger.debug "Sending to #{destination}: #{msg.inspect}"
    @mq.queue(destination, :durable => true).publish([msg].to_json, :persistent => true)
  end

  if block_given?
    op = Operation.new &callback
    MQRPC::logger.debug "New operation for #{msg.id}"
    @message_operations[msg.id] = op
    return op
  end
end

#sendmsg_topic(key, msg) ⇒ Object 



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# File 'lib/mqrpc/agent.rb', line 311

def sendmsg_topic(key, msg)
  if (msg.is_a?(RequestMessage) and msg.id == nil)
    msg.generate_id!
  end
  msg.timestamp = Time.now.to_f

  data = msg.to_json
  @mq.topic(@config.mqexchange).publish(data, :key => key)
end

#start_amqp ⇒ Object

def initialize



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# File 'lib/mqrpc/agent.rb', line 110

def start_amqp
  @amqpthread = Thread.new do 
    Thread.current[:name] = "AMQP"
    # Create connection to AMQP, and in turn, the main EventMachine loop.
    amqp_config = {:host => @config.mqhost,
                   :port => @config.mqport,
                   :user => @config.mquser,
                   :pass => @config.mqpass,
                   :vhost => @config.mqvhost,
                  }
    AMQP.start(amqp_config) do
      @startup_mutex.synchronize do
        @mq = MQ.new
        # Notify the main calling thread (MessageSocket#initialize) that
        # we can continue
        @amqp_ready = true
        @startup_condvar.signal
      end

      MQRPC::logger.info "Subscribing to main queue #{@id}"
      subscribe(@id)
      
      # TODO(sissel): make this a deferred thread that reads from a Queue
      EM.defer { handle_subscriptions }

      EM.add_periodic_timer(1) do
        @outbuffer.each_key { |dest| flushout(dest) }
        @outbuffer.clear
      end
    end # AMQP.start
  end
end

#start_receiver ⇒ Object

def start_amqp



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# File 'lib/mqrpc/agent.rb', line 143

def start_receiver
  Thread.new do 
    Thread.current[:name] = "receiver"
    while true
      header, message = @receive_queue.pop
      handle_message(header, message)
    end
  end
end

#subscribe(name) ⇒ Object

def start_receiver



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# File 'lib/mqrpc/agent.rb', line 153

def subscribe(name)
  MQRPC::logger.info "Wanting to subscribe to queue #{name}"
  @want_subscriptions << [:queue, name]
end

#subscribe_topic(name) ⇒ Object

def unsubscribe



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# File 'lib/mqrpc/agent.rb', line 175

def subscribe_topic(name)
  @want_subscriptions << [:topic, name]
end

#unsubscribe(name) ⇒ Object

def subscribe



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# File 'lib/mqrpc/agent.rb', line 158

def unsubscribe(name)
  exchange = @mq.topic(@config.mqexchange, :durable => true)
  mq_q = @mq.queue(name, :durable => true)
  mq_q.bind(exchange, :key => "*")

  op = Operation.new
  mq_q.unsubscribe { op.finished }
  op.wait_until_finished
  @queues.delete(name)

  #mq_q.unsubscribe { @queues.delete(name) }
  ## wait for unsubscribe to finish; it's async
  #while @queues.member?(name)
    #sleep(0.1)
  #end
end