The Message Replay Server stores published messages and allows application programs to replay messages later and/or subscribe to incoming messages.
The Message Replay Server will subscribe to a range of topics on the Broker (which can be specified by the system administrator). On arrival, messages are tagged with a time-stamp and message sequence number (unique per message per topic) and saved to non-volatile storage (typically a database).
Applications using the Replay Subscriber API can request a range of publications which can span from the earliest held in storage to any point in the future (including ‘forever’). An application may request purely historic publications, or publications as they arrive, or a combination of these to replay historic publications until they catch up to the current incoming publication stream, then continue, possibly indefinitely. The switch-over from historic publications to the incoming publication stream will be transparent to the application.
Topics can be specified using a regular Broker topic specifier (which can include the ‘+’ & ‘#’ wild-cards). Ranges can be specified using a mixture of time or sequence number.
The publication stream can be sampled by time or message number (e.g. every 30 seconds or every 10th message) on a per topic or aggregated basis.
The rate at which the replayed publications are delivered can be specified as: their original timing (e.g. 24 hours worth of messages would be delivered over 24 hours), throttled to no more than ‘x’ publications per millisecond, or as soon as possible (the default).
Subscriber Catch-Up - You might have a trading application that uses publish/subscribe to receive stock market data. If this application is not always available, or if the trader who uses the application is not always present, then the application can use message replay to receive relevant messages which were published while the application was unavailable, and to then continue to receive new messages as they are captured by the Replay Server. This is somewhat like a durable subscription but with the benefit that it works with the high performance MQ real-time protocol (although messages might be lost if the Replay Server fails before the message has been asynchronously written to the non-volatile storage).
Trend Analysis - With its ability to replay historical messages over an arbitrary time period that will catch up with the current message flow, the Replay System can provide data for ad-hoc trend analysis. A user of such a system could choose to monitor various topics, starting from say, an hour ago.
Data Monitoring - You might have an application that analyzes sensor data related to geological events. To minimize data volumes you might want to sample this sensor data sufficiently often to spot an interesting event, such as an earthquake, but not often enough to fully analyze that event. Having spotted the interesting event, your application can use message replay to receive all the detailed messages that are published shortly before and shortly after that event.
Application Testing - You might want to test and improve a new application using real world data. You can use message replay to capture a typical sample of this real world data, which your test applications can then repeatedly receive. Your test applications can choose to receive the captured messages either at a fixed arrival rate unrelated to their real world arrival times, or with built-in delays so that they arrive with the same timing pattern as in the real world.
SKILL LEVEL REQUIRED
• Competent in JMS programming, JNDI, Event / Message Broker & MQ.
• Good understanding of PubSub.
• Able to administer DB2.
NEW IN THIS RELEASE
• Minor defects fixed.
• Documentation updated.
Author: WebSphere MQ Replay Team, Hursley
Last updated: 01Aug07
Current Version: 1.2
• Please note that the version number shown in the right-hand pane is the version of the MQ or WBI product that this SupportPac applies to. The date is the last webpage refresh.
• IBM WebSphere Message Broker V6.0 or V6.1
• Java 1.5.0
• Any of the following operating systems: Windows, AIX, Solaris or Linux.
Please refer to the User Guide for further details
The developers of this SupportPac would be very interested to know how you might use it, in order to help with future development.
Please use the 'Rate this Page' section at the end of the page and use the comments box indicating your name, organisation, email address and proposed usage. We would be grateful if you could take the time to provide any of this information.
You must install your Replay Server on the same operating system image as a WebSphere Business Integration Event/Message Broker. This means that your Replay Server can use the same DB2 database as your WebSphere Business Event/Integration Message Broker (although the Java runtime environment must be version 1.4 or higher). Performance and backup should be considered before you choose this option, however.
Unzip the “io03.zip” file, or untar and uncompress the “io03.tar.Z” file into your chosen installation directory, and follow the configuration instructions in:
(See also '<install-dir>/doc/readme.txt' for any late additions to the documentation).
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Category 3 WebSphere MQ SupportPacs are supplied under the standard terms and conditions provided by the International Program License Agreement (IPLA) and thus carry program defect service.
Please read the license files that accompany the SupportPac to ensure you understand the conditions under which the SupportPac is provided. No Proof of Entitlement is required for this SupportPac.
If you encounter what you believe to be a defect with the SupportPac you may request Program Services by reporting the problem via the same defect reporting channel you employ for the WebSphere MQ server product with which you are using the SupportPac.
This SupportPac has service support for as long as the WebSphere Business Integration Broker V6.0 or V6.1 remains in service. Refer to http://www.ibm.com/software/info/supportlifecycle/ for the relevant service information. It is only supported with MQ platforms which are themselves supported.