Monday, October 25, 2021

MassTransit - Stop handling erroneous messages

By default when a MassTransit consumer fails to handle a message (and throws an exception), the message is moved to an _error queue (prefixed by the receive endpoint queue name). This is OK for transient exceptions but probably not what you want when you have a bug in your system or there is another reason why none of the messages can be handled succesfully.

In that case, another feature of MassTransit becomes handy; the kill switch.

A Kill Switch is used to prevent failing consumers from moving all the messages from the input queue to the error queue. By monitoring message consumption and tracking message successes and failures, a Kill Switch stops the receive endpoint when a trip threshold has been reached.

You can configure a kill switch for a specific endpoint or for all receiver endpoints on the bus.

Here is a short example on how to configure the kill switch for all receiver endpoints:


In the above example, the kill switch will activate after 10 messages have been consumed. If the ratio of failures/attempts exceeds 15%, the kill switch with trip and stop the receive endpoint. After 1 minute, the receive endpoint will be restarted. Once restarted, if exceptions are still observed, the receive endpoint will be stopped again for 1 minute.

If you want to learn more about this feature, check out this video by Chris Patterson, the creator of Masstransit: