class NebulousStomp::StompHandler

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).

Attributes

conn[R]

Public Class Methods

new(connectHash=nil, testConn=nil) click to toggle source

Initialise StompHandler by passing the parameter hash.

# File lib/nebulous_stomp/stomp_handler.rb, line 23
def initialize(connectHash=nil, testConn=nil)
  @stomp_hash = connectHash ? connectHash.dup : nil
  @test_conn  = testConn
  @conn       = nil
end

Public Instance Methods

calc_reply_id() click to toggle source

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

# File lib/nebulous_stomp/stomp_handler.rb, line 206
def calc_reply_id
  return nil unless nebulous_on?
  fail ConnectionError, "Client not connected" unless @conn

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

end
connected?() click to toggle source

return true if we are connected to the STOMP server

# File lib/nebulous_stomp/stomp_handler.rb, line 66
def connected?
  !!(@conn && @conn.open?())
end
listen(queue, logid="") { |from_stomp\| ... } click to toggle source

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.

It runs in a thread; if you want it to stop, just stop waiting for it.

# File lib/nebulous_stomp/stomp_handler.rb, line 86
def listen(queue, logid="")
  return unless nebulous_on?
  NebulousStomp.logger.info(__FILE__) {"Subscribing to #{queue}"}

  Thread.new do
    stomp_connect unless @conn

    # 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...
    @conn.publish( queue, "boo" )
    @conn.subscribe( queue, {ack: "client-individual"} )

    loop do
      begin
        msg = @conn.poll()
        log_msg(msg, logid)
        ack(msg)

        yield Message.from_stomp(msg) \
          unless msg.body == 'boo' \
              || msg.respond_to?(:command) && msg.command == "ERROR"

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

  end # of thread

end
listen_with_timeout(queue, timeout, logid="") { |from_stomp| ... } click to toggle source

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.

# File lib/nebulous_stomp/stomp_handler.rb, line 128
def listen_with_timeout(queue, timeout, logid="")
  return unless nebulous_on?
  NebulousStomp.logger.info(__FILE__) {log_helper logid, "Subscribing to #{queue} with timeout #{timeout}"}

  stomp_connect unless @conn
  id = rand(10000)

  @conn.publish( queue, "boo" )
  
  done = false
  time = Time.now

  @conn.subscribe(queue, {ack: "client-individual"}, id) 
  NebulousStomp.logger.debug(__FILE__) {log_helper logid, "subscribed"}

  loop do
    begin
      msg = @conn.poll()

      if msg.nil?
        # NebulousStomp.logger.debug(__FILE__) {log_helper logid, "Empty message, sleeping"}
        sleep 0.2
      else
        log_msg(msg, logid)

        if msg.respond_to?(:command) && msg.command == "ERROR"
          NebulousStomp.logger.error(__FILE__) {log_helper logid, "Error frame: #{msg.inspect}" }
          ack(msg)
        elsif msg.respond_to?(:body) && msg.body == "boo"
          ack(msg)
        else
          done = yield Message.from_stomp(msg) 
          if done
            NebulousStomp.logger.debug(__FILE__) {log_helper logid, "Yield returns true"}
            ack(msg)
          end
        end

      end # of else

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

    break if done

    if timeout && (time + timeout < Time.now)
      NebulousStomp.logger.debug(__FILE__) {log_helper logid, "Timed out"}
      break
    end
  end

  NebulousStomp.logger.debug(__FILE__) {log_helper logid, "Out of loop. done=#{done}"}

  @conn.unsubscribe(queue, {}, id)

  fail NebulousTimeout unless done
end
nebulous_on?() click to toggle source

return true if Nebulous is turned on in the parameters

# File lib/nebulous_stomp/stomp_handler.rb, line 73
def nebulous_on?
  !!(@stomp_hash && !@stomp_hash.empty?)
end
send_message(queue, mess, logid="") click to toggle source

Send a Message to a queue; return the message.

# File lib/nebulous_stomp/stomp_handler.rb, line 190
def send_message(queue, mess, logid="")
  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 @conn

  headers = mess.headers_for_stomp.reject{|k,v| v.nil? || v == "" }
  @conn.publish(queue, mess.body_for_stomp, headers)
  mess
end
stomp_connect(logid="") click to toggle source

Connect to the STOMP client.

# File lib/nebulous_stomp/stomp_handler.rb, line 32
def stomp_connect(logid="")
  return self unless nebulous_on?
  NebulousStomp.logger.info(__FILE__) {log_helper logid, "Connecting to STOMP"} 
  NebulousStomp.logger.debug(__FILE__) {log_helper logid, @stomp_hash.inspect}

  @conn = @test_conn || Stomp::Connection.new(@stomp_hash)
  fail ConnectionError, "Stomp Connection failed" unless @conn.open?()

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

  self
rescue => err
  raise ConnectionError, err
end
stomp_disconnect(logid="") click to toggle source

Drop the connection to the STOMP Client

# File lib/nebulous_stomp/stomp_handler.rb, line 53
def stomp_disconnect(logid="")
  if @conn
    NebulousStomp.logger.info(__FILE__) {log_helper logid, "STOMP Disconnect"}
    @conn.disconnect() if @conn
    @conn = nil
  end

  self
end

Private Instance Methods

ack(message, headers={}) click to toggle source

Borrowed from Stomp::Client.ack()

# File lib/nebulous_stomp/stomp_handler.rb, line 231
def ack(message, headers={})

  case @conn.protocol
    when Stomp::SPL_12
      id = 'ack'
    when Stomp::SPL_11
      headers = headers.merge(:subscription => message.headers['subscription'])
      id = 'message-id'
    else
      id = 'message-id'
  end

  @conn.ack(message.headers[id], headers)
end
log_helper(logid, message) click to toggle source
# File lib/nebulous_stomp/stomp_handler.rb, line 218
def log_helper(logid, message)
  "[#{logid}|#{Thread.object_id}] #{message}"
end
log_msg(message, logid) click to toggle source
# File lib/nebulous_stomp/stomp_handler.rb, line 222
def log_msg(message, logid)
  NebulousStomp.logger.debug(__FILE__) do
    b = message.respond_to?(:body) ? message.body.to_s[0..30] : nil
    h = message.respond_to?(:headers) ? message.headers.select{|k,v| k.start_with?("neb-") }.to_h : {}
    log_helper logid, "New message neb: #{h} body: #{b}"
  end
end