Anypoint MQ Messages Stuck in Inflight Status for Extended Periods After a Restart

SYMPTOM

The Mule application has stopped consuming messages, and this issue persists even after a restart. The number of inflight messages remains constant, indicating that these messages are not being released for hours.

CAUSE

This behavior can occur when the acknowledgment timeout for the queue or MQ subscriber operation is set to an extended duration (i.e., hours). While the maximum acknowledgment timeout can be configured to 12 hours, it is strongly discouraged to set the timeout to 2 or 3 hours or more. When the acknowledgment timeout is excessively high, inflight messages may remain in the inflight for hours before being returned to the queue for reprocessing.

SOLUTION

It is crucial to understand the implications of setting a high acknowledgment timeout. The default acknowledgment timeout is set to 2 minutes, and it is generally recommended to adjust this value only when necessary, typically to durations like 3, 5, or 10 minutes, to avoid unnecessary message reprocessing.

For best practices, consider keeping the acknowledgment timeout to a more reasonable duration. Setting the acknowledgment timeout to several hours (e.g., 7 or 10 hours) is quite abnormal and may result in messages remaining in inflight status for an extended period if the consumer does not issue ACK or NACK calls.

For additional information, please refer to the following link: Anypoint MQ Message Getting Processed Twice.