ActiveMQ in Action

• stephansun

  2011-10-29
  Using the request/reply pattern, envision that there are thousands of requestsentering the broker every second from many clients, all distributed across many hosts.In a production system, more than just a single broker instance would be used for thepurposes of redundancy, failover, and load balancing. These brokers would also bedistributed across many hosts. The only way to handle this many requests would be touse many workers. Producers can always send messages much faster than a consumercan receive and process them, so lots of workers would be needed, all of them spreadout across many hosts as well. The advantage of using many workers is that each onecan go up and down at will, and the overall system itself isn’t affected. The producersand workers would continue to process messa...
• stephansun

  2011-10-28
  7.3 Implementing request/reply with JMSAs described in earlier chapters, messaging is all about the decoupling of senders fromreceivers. Messages are sent by one process to a broker, and messages are received froma broker by a different process in an asynchronous manner. One style of system architecturethat can be implemented using JMS is known as request/reply. From a high level,a request/reply scenario involves an application that sends a message (the request)and expects to receive a message in return (the reply). Traditionally, such a systemdesign was implemented using a client-server architecture, with the server and the clientcommunicating in a synchronous manner across a network transport (TCP, UDP,and so on). This style of architecture certainly has scalability limitations,...
• stephansun

  2011-10-28
  Request/reply messaging in JMS applicationsAlthough the JMS spec doesn’t define request/reply messaging as a formal messagingdomain, it does provide some message headers and a couple of convenienceclasses for handling basic request/reply messaging. Request/reply messaging is anasynchronous back-and-forth conversational pattern utilizing either the PTP domain orthe pub/sub domain through a combination of the JMSReplyTo and JMSCorrelationIDmessage headers and temporary destinations. The JMSReplyTo specifies the destinationwhere a reply should be sent, and the JMSCorrelationID in the reply messagespecifies the JMSMessageID of the request message. These headers are used tolink the reply message(s) to the original request message. Temporary destinationsare those that are created only ...
• stephansun

  2011-10-28
  Message-oriented middleware (MOM) is best described as a category of software for communication in an asynchronous, loosely-coupled, reliable, scalable, and secure manner among distributed applications or systems. MOMs were an important concept in the distributed computing world. They allowed application-to-application communication using APIs provided by each vendor, and began to deal with many issues in the distributed system space.
• stephansun

  2011-10-28
  The purpose of enterprise messaging was to transfer data among disparate systems by sending messages from one system to another. There have been numerous technologies for various forms of messaging through the years, including the following list:·Solutions for remote procedure calls (RPC) such as COM, CORBA, DCE, and EJB·Solutions for event notification, inter-process communication, and message queuing that are baked into operating systems such as FIFO buffers, message queues, pipes, signals, sockets, and others·Solutions for a category of middleware that provides asynchronous, reliable message queuing such as IBM WebSphere MQ, SonicMQ, TIBCO Rendezvous, and Apache ActiveMQ, commonly used for Enterprise Application Integration (EAI) purposes