Class: NebulousStomp::StompHandler

Inherits:
Object
  • Object
show all
Defined in:
lib/nebulous_stomp/stomp_handler.rb

Overview

A Class to deal with talking to STOMP via the Stomp gem.

You shouldn’t ever need to instantiate this yourself. For listening to messages and responding, use NebulousStomp::Listener. For sending a message and waiting for a response, you want NebulousStomp::Request (passing it a NebulousStomp::Message).

Direct Known Subclasses

StompHandlerNull

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(connectHash = nil, testClient = nil) ⇒ StompHandler

Initialise StompHandler by passing the parameter hash.



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# File 'lib/nebulous_stomp/stomp_handler.rb', line 67

def initialize(connectHash=nil, testClient=nil)
  @stomp_hash  = connectHash ? connectHash.dup : nil
  @test_client = testClient
  @client      = nil
end

Instance Attribute Details

#client ⇒ Object (readonly)

Returns the value of attribute client.



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# File 'lib/nebulous_stomp/stomp_handler.rb', line 17

def client
  @client
end

Class Method Details

.with_timeout(secs) ⇒ Object

:call-seq:

StompHandler.with_timeout(secs) -> (nil)

Run a routine with a timeout.

Example:

StompHandler.with_timeout(10) do |r|
  sleep 20
  r.signal
end

Use r.signal to signal when the process has finished. You need to arrange your own method of working out whether the timeout fired or not.

Also, please note that when the timeout period expires, your code will keep running. The timeout will only be honoured when your block completes. This is very useful for Stomp.subscribe, but probably not for anything else…

There is a Ruby standard library for this, Timeout. But there appears to be some argument as to whether it is threadsafe; so, we roll our own. It probably doesn’t matter since both Redis and Stomp do use Timeout. But.



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# File 'lib/nebulous_stomp/stomp_handler.rb', line 48

def with_timeout(secs)
  mutex    = Mutex.new
  resource = ConditionVariable.new

  t = Thread.new do
    mutex.synchronize { yield resource }
  end
  mutex.synchronize { resource.wait(mutex, secs) }

  nil
end

Instance Method Details

#calc_reply_id ⇒ Object

Return the neb-reply-id we’re going to use for this connection



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# File 'lib/nebulous_stomp/stomp_handler.rb', line 222

def calc_reply_id
  return nil unless nebulous_on?
  fail ConnectionError, "Client not connected" unless @client

  @client.connection_frame().headers["session"] \
    << "_" \
    << Time.now.to_f.to_s

end

#connected? ⇒ Boolean

return true if we are connected to the STOMP server

Returns:

  • (Boolean) 


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# File 'lib/nebulous_stomp/stomp_handler.rb', line 109

def connected?
  @client && @client.open?
end

#listen(queue) ⇒ Object

Block for incoming messages on a queue. Yield each message.

This method automatically consumes every message it reads, since the assumption is that we are using it for the request-response use case. If you don’t want that, try listen_with_timeout(), instead.

Note that the blocking happens in a thread somewhere inside the STOMP client. I have no idea how to join that, and if the examples on the STOMP gem are to be believed, you flat out can’t – the examples just have the main thread sleeping so that it does not termimate while the thread is running. So to use this make sure that you at some point do something like:

loop { sleep 5 }



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# File 'lib/nebulous_stomp/stomp_handler.rb', line 134

def listen(queue)
  return unless nebulous_on?
  NebulousStomp.logger.info(__FILE__) {"Subscribing to #{queue}"}

  stomp_connect unless @client

  # Startle the queue into existence. You can't subscribe to a queue that
  # does not exist, BUT, you can create a queue by posting to it...
  @client.publish( queue, "boo" )

  @client.subscribe( queue, {ack: "client-individual"} ) do |msg|
    begin
      @client.ack(msg)
      yield Message.from_stomp(msg) unless msg.body == 'boo'
    rescue =>e
      NebulousStomp.logger.error(__FILE__) {"Error during polling: #{e}" }
    end
  end

end

#listen_with_timeout(queue, timeout) ⇒ Object

As listen() but give up after yielding a single message, and only wait for a set number of seconds before giving up anyway.

The behaviour here is slightly different than listen(). If you return true from your block, the message will be consumed and the method will end. Otherwise it will continue until it sees another message, or reaches the timeout.

Put another way, since most things are truthy – if you want to examine messages to find the right one, return false from the block to get another.



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# File 'lib/nebulous_stomp/stomp_handler.rb', line 166

def listen_with_timeout(queue, timeout)
  return unless nebulous_on?
  NebulousStomp.logger.info(__FILE__) { "Subscribing to #{queue} with timeout #{timeout}" }

  stomp_connect unless @client
  @client.publish( queue, "boo" )
  done = false

  StompHandler.with_timeout(timeout) do |resource|
    @client.subscribe( queue, {ack: "client-individual"} ) do |msg|

      begin
        if msg.body == "boo"
          @client.ack(msg)
        else
          done = yield Message.from_stomp(msg) 
          @client.ack(msg) if done
        end

      rescue =>e
        NebulousStomp.logger.error(__FILE__) {"Error during polling: #{e}" }
      end

      if done
        # Not that this seems to do any good when the Stomp gem is in play
        resource.signal 
        break
      end

    end # of Stomp client subscribe block

    resource.signal if done #or here. either, but.
  end # of with_timeout

  fail NebulousTimeout unless done
end

#nebulous_on? ⇒ Boolean

return true if Nebulous is turned on in the parameters

Returns:

  • (Boolean) 


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# File 'lib/nebulous_stomp/stomp_handler.rb', line 116

def nebulous_on?
  @stomp_hash && !@stomp_hash.empty?
end

#send_message(queue, mess) ⇒ Object

Send a Message to a queue; return the message.



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# File 'lib/nebulous_stomp/stomp_handler.rb', line 206

def send_message(queue, mess)
  return nil unless nebulous_on?
  fail NebulousStomp::NebulousError, "That's not a Message" \
    unless mess.respond_to?(:body_for_stomp) \
        && mess.respond_to?(:headers_for_stomp)

  stomp_connect unless @client

  headers = mess.headers_for_stomp.reject{|k,v| v.nil? || v == "" }
  @client.publish(queue, mess.body_for_stomp, headers)
  mess
end

#stomp_connect ⇒ Object

Connect to the STOMP client.



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# File 'lib/nebulous_stomp/stomp_handler.rb', line 76

def stomp_connect
  return self unless nebulous_on?
  NebulousStomp.logger.info(__FILE__) {"Connecting to STOMP"} 

  @client = @test_client || Stomp::Client.new( @stomp_hash )
  fail ConnectionError, "Stomp Connection failed" unless connected?

  conn = @client.connection_frame()
  if conn.command == Stomp::CMD_ERROR
    fail ConnectionError, "Connect Error: #{conn.body}"
  end

  self
rescue => err
  raise ConnectionError, err
end

#stomp_disconnect ⇒ Object

Drop the connection to the STOMP Client



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# File 'lib/nebulous_stomp/stomp_handler.rb', line 96

def stomp_disconnect
  if @client
    NebulousStomp.logger.info(__FILE__) {"STOMP Disconnect"}
    @client.close if @client
    @client = nil
  end

  self
end