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Messaging with RabbitMQ and AMQP


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This presentation talks about RabbitMQ and AMQP. It also covers web-STOMP to interface JavaScript.

This presentation talks about RabbitMQ and AMQP. It also covers web-STOMP to interface JavaScript.

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  • 1. Messaging with AMQP and RabbitMQ Eberhard WolffArchitecture and Technology Manager adesso AG
  • 2. Overview•  Why Messaging, AMQP and RabbitMQ•  Basic AMQP•  Exchanges•  More on Spring-AMQP
  • 3. Why Messaging?•  Decoupling –  Data, no action i.e. receiver Component can react arbitrarily –  Asynchronous i.e. decoupled by time•  Reliable –  Message can be stored-and- Component forwarded Messages –  Redelivery until message processed•  Solves typical problems of distributed systems
  • 4. Why Messaging?•  But: Requires different architecture•  Very different from calling remote methods•  Asynchronous•  AJAX has the same model•  See for example “Patterns of Enterprise Integration”
  • 5. Why AMQP?•  Open standard protocol•  Standard wire protocol•  i.e. just one client library – no matter which implementation you are using•  Less vendor lock in•  Efficient –  Binary wire protocol•  Support in all major languages•  Supported on most OS platforms
  • 6. What about JMS?•  JMS has been the default for Java messaging system for 10+ years•  But: –  Only standardized on the API level –  Less flexible than AMQP•  Mapping AMQP/JMS is being defined•  Some products support both
  • 7. Why Rabbit?•  Because it has a kewl name•  Numerous protocols supported•  Most popular choice on EC2•  Foundation for demanding systems e.g. NASA’s cloud initiative Nebula•  Implemented in Erlang•  Clustering built in•  Currently in 2.8.7•  Supports AMQP 0.8, 0.9, 0.9.1•  1.0 as a prototype Plug In
  • 8. Broad Support in RabbitMQ
  • 9. Broad Support in the JVM Space•  Grails Plug In•  Java Client•  Scala / Lift support•  We will discuss Spring support in detail•  Spring AMQP project 1.1.2• amqp
  • 10. Why Erlang?•  Originally designed for telephone switches by Ericsson•  Much easier to develop scalable and fault tolerant systems (by factors)•  See Motorola presentation: cpp-and-erlang-for-motorola-telecoms-software•  Good tool for reliable and scalable systems
  • 11. Erlang‘s Model MonitorLink to monitor,restart Light Light Light weight Messages weight Messages weight process process process with with with state state state
  • 12. Why Erlang?•  Let it crash –  If a process fails, it can be easily restarted –  Different approach to fault tolerance –  Otherwise lots of error handling•  Message Passing in the Core –  RabbitMQ is a messaging system…•  Light-weight process model –  Scales to massive numbers of connections
  • 13. Basic AMQP
  • 14. Very Basic AMQP•  Queues: Store messages•  Queues might be –  Durable: Survive server restarts –  Exclusive: For one connection –  autoDelete: Deleted if connection closes•  All resources are dynamic•  Producer sends a message to a Queue
  • 15. CodeConnectionFactory conFactory = new CachingConnectionFactory ("localhost"); RabbitAdmin admin = new RabbitAdmin(conFactory); admin.declareQueue(
 new Queue("myQueue", false, true, true)); RabbitTemplate template = new RabbitTemplate(conFactory); template.convertAndSend("myQueue", "Hi AMQP!"); String receive = (String) template.receiveAndConvert("myQueue"); Assert.assertEquals("Hi AMQP!", receive);
  • 16. Spring’s MessageConverter•  Messages are binary data•  RabbitTemplate uses MessageConverter to convert between objects and messages•  E.g. JSON, Serialization, XML …•  Can also send binary data if preferred
  • 17. Basics of AMQP•  Sending messages directly to queues is not enough•  What about e.g. pub / sub?•  Exchange: Route messages (stateless)•  Example used the default exchange•  More dynamic, flexible and cleaner than JMS
  • 18. AMQP  in  a  nutshell  Exchange routes messageStatelessUsually created by producerNo queue: Message discarded X Binding binds an Exchange to a Queue Queues buffer messages Usually created by consumer
  • 19. AMQP  in  a  nutshell  Producer and Consumer might be written in Java, C#,Python, Ruby … C P X C AMQP RabbitMQ AMQP protocol protocol
  • 20. Exchanges
  • 21. X Exchange: Route Messages•  The type of Exchange defines the routing algorithm•  Binding provides selector for routing•  Exchange is addressed by name•  Some standard types•  Can provide additional ones
  • 22. X Fanout Exchange•  Broadcast to all bound queues•  Fast•  Simple•  amq.fanout is mandatory•  To broadcast information
  • 23. X Fanout Exchange CP X C Fanout C
  • 24. Queue fanoutQueue = new Queue("fanoutQueue"); admin.declareQueue(fanoutQueue); FanoutExchange fanoutExchange= new FanoutExchange("myFanout"); admin.declareExchange(fanoutExchange); admin.declareBinding( BindingBuilder.bind(fanoutQueue). to(fanoutExchange)); template.setExchange("myFanout"); template.convertAndSend("Hi Fanout!"); String receive = (String) template.receiveAndConvert("fanoutQueue"); Assert.assertEquals("Hi Fanout!", receive);
  • 25. X Direct Exchange•  Routing based on one routing key• and the default Exchange (no name) always exist•  To send work orders to a specific worker
  • 26. Direct Exchangenormalexpress Direct Exchange C express P X C normal C
  • 27. X Topic Exchange•  Routing based on routing pattern•  amq.topic is mandatory•  E.g. for public / subscribe scenarios
  • 28. Topic Exchange   order.DEinvoice.USD Topic Exchange order.* P X C invoice.* C
  • 29. X Headers Exchange•  Routing based on one or more headers and an expression•  amqp.match is mandatory•  Complex routing roles
  • 30. Other Features•  Message can be persistent•  Request / response using correlations possible•  Redelivery / acknowledgement possible•  Clustering with e.g. Linux HA possible•  ...or send message through multiple channels and drop duplicates
  • 31. More on Spring AMQP
  • 32. The MessageListener•  So far: Calling receive() on RabbitTemplate•  Needed: Something that is called when a new message appears
  • 33. Spring’s MessageListener Container•  Spring provides lightweight containers to call MessageListeners•  SimpleMessageListenerContainer•  Advanced scheduling and endpoint management options available•  i.e. thread pools, concurrent consumers, transaction handling
  • 34. Springs message-driven objects•  MessageListener means the receiver depends on Spring API•  Why not just a POJO?
  • 35. Message-driven POJO<rabbit:listener-container connection-factory="connectionFactory“ message-converter="jsonMessageConverter"> <rabbit:listener ref="consumer" method="consume" queue-names="my.amqp.queue2" /></rabbit:listener-container>•  Takes a POJO and makes it a MessageListener•  i.e. calls consume on Bean consume
  • 36. @Component Consumer codepublic class Consumer { public String consume(String message) { return …; } }•  No dependency on AMQP!•  But: What about the result of the method?•  Send to the Reply-To address given in message properties with same correlationId as original method
  • 37. Client CodeString response = (String) rabbitTemplate.convertSendAndReceive( "my.fanout", "", "test");•  Message sent to destination with routing key•  Reply-To set to exclusive, autodelete, non- durable queue•  Response received through Reply-To converted and returned•  Easy request-response!•  Beware of potential latency
  • 38. Web Messaging
  • 39. Web Messaging•  Goal: Send / receive messages in the browser•  With JavaScript•  I.e. JavaScript must receive message•  HTML5 browser: WebSockets•  Pre HTML5: long polling etc
  • 40. SockJS•  Unifies Web Sockets, long polling etc•  Unified JavaScript API•  Server component•  Can run embedded in RabbitMQ
  • 41. STOMP•  Simple (or Streaming) Text Oriented Message Protocol•  Very simple protocol for Message Oriented Middleware•  STOMP over SockJS•  See 2012/05/14/introducing-rabbitmq-web- stomp/
  • 42. STOMPJavaScript Java SockJS AMQP C# Web Sockets … Long Polling
  • 43. JavaScript CodeWebSocketStompMock = SockJS;var client = Stomp.client(http://localhost:55674/stomp);…client.send(/topic/test, {}, data);…client.connect(guest, guest, function(x) { id = client.subscribe("/topic/test", function(message) { if (message.body) { alert("got message with body " + message.body) } AMQP: Topic exchange }); amq.topic}); with routing key test
  • 44. Conclusion: AMQP•  Ubiquitous Messaging•  AMQP: Protocol standard•  Better scalability•  Dynamic resources
  • 45. Conclusion: Spring AMQP•  Easy to use•  Flexible (e.g. message encoding)•  Allows scalable message handling•  Full support for AMQP and RabbitMQ
  • 46. Conclusion: Web Messaging•  Simple API•  Works on older browsers•  Single server – also for messaging•  Erlang is very well able to handle the many connections
  • 47. More••  Also a .NET version available•  …and support in Spring Integration•  …and there is very similar Spring JMS support• topologies-for-performance-and-scalability-with- rabbitm• –  CDI event / AMQP integration –  Managed publisher and consumer