Dear Rabbitters,<div><br></div><div>i was working with a client recently and they asked whether RabbitMQ had a journaling feature. The client was used to working with MSMQ which has such a feature and allows them to get a view of queue usage history, such as message deposited to queue, message read from queue, etc. The question came up in the context of debugging a message processing code path where we couldn't readily tell whether the message had been deposited to the queue and was being nabbed by a dispatcher faster than we could see or whether the message was never arriving at the queue at all. The client observed that with a journaling feature there would be no need to introduce more debugging statements into application code. So, i'm passing their question along to you.</div>
<div><br></div><div>In this connection i will raise a point i've made before to this community. With such a journaling log i can take off-the-shelf tools and probe message traces for correctness properties. Specifically, i have already demonstrated with a little project called XTrace that with an xml-based message history format we can use schema conformance to probe message trace for properties. The basic idea is to encode a property as a schema. The beauty of this approach is that it is post facto and does not require a specific schema to govern message trace history. Rather, an application programmer devises schema to investigate the message trace history to look for conformance to protocol or validate a guess about where/how things might be going awry.</div>
<div><br></div><div>i mention this latter point in connection with the client's question to amplify the argument for the feature. Their sense of the separation of concerns and independent value for RabbitMQ is right on track and only the tip of the iceberg of what can be done.</div>
<div><br></div><div>Best wishes,</div><div><br></div><div>--greg<br clear="all"><br>-- <br>L.G. Meredith<br>Managing Partner<br>Biosimilarity LLC<br>7329 39th Ave SW<div>Seattle, WA 98136<br><br>+1 206.650.3740<br><br><a href="http://biosimilarity.blogspot.com" target="_blank">http://biosimilarity.blogspot.com</a></div>
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