How do you troubleshoot memory alarms in RabbitMQ?

A memory alarm fires when a node's memory use crosses vm_memory_high_watermark, and RabbitMQ responds by blocking publishers on the affected node until memory drops - a state visible in the management UI as flow control.

1. Confirm the alarm with rabbitmqctl status or the management UI's node page, which shows current memory use versus the watermark.
2. Find the culprit queues using rabbitmqctl list_queues name messages memory to spot queues holding an unexpectedly large backlog.
3. Check for stuck consumers - a large "unacked" count often means a consumer stopped acking, so messages pile up in memory waiting for acknowledgment.
4. Reduce memory pressure by draining the backlog, enabling lazy-queue-style behavior for large queues so messages page to disk sooner, or scaling out consumers.
5. Only as a last resort, raise vm_memory_high_watermark, and only after confirming the node actually has the physical RAM headroom to support it.

Treat the watermark increase as a temporary safety valve, not a fix - the underlying backlog or slow-consumer problem still needs addressing.

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