Queue Holding Memory even with 0 queue size

[Priyatham]

Hi,

 Please help how to overcome this issue, We have as RHEL 9 system with Rabbitmq 3.12.13 and erlang 26.2.2

Below is the overall Memory breakdown  and queue memory shows >400Mb for each queue 

how can i clear this and fix it permanently

[root@]# rabbitmq-diagnostics memory_breakdown
Reporting memory breakdown on node rabbit@...
queue_procs: 10.7166 gb (65.23%)
reserved_unallocated: 5.5706 gb (33.91%)
allocated_unused: 0.0431 gb (0.26%)
code: 0.0376 gb (0.23%)
other_system: 0.0235 gb (0.14%)
other_proc: 0.0229 gb (0.14%)
plugins: 0.0043 gb (0.03%)
other_ets: 0.0027 gb (0.02%)
mgmt_db: 0.0018 gb (0.01%)
atom: 0.0015 gb (0.01%)
metrics: 0.0015 gb (0.01%)
msg_index: 0.0012 gb (0.01%)
binary: 0.001 gb (0.01%)
mnesia: 0.001 gb (0.01%)
quorum_ets: 0.0 gb (0.0%)
connection_other: 0.0 gb (0.0%)
quorum_queue_procs: 0.0 gb (0.0%)
quorum_queue_dlx_procs: 0.0 gb (0.0%)
stream_queue_procs: 0.0 gb (0.0%)
stream_queue_replica_reader_procs: 0.0 gb (0.0%)
connection_readers: 0.0 gb (0.0%)
connection_writers: 0.0 gb (0.0%)
connection_channels: 0.0 gb (0.0%)
queue_slave_procs: 0.0 gb (0.0%)
stream_queue_coordinator_procs: 0.0 gb (0.0%)

[jo...@cloudamqp.com]

Hi,

Perform a GC (rabbitmqctl force_gc)

Set a policy to use classic queues version 2.

Upgrade to RabbitMQ 3.13.6.

/Johan

[Priyatham]

Hi Johan,

Thanks for you inputs, would like to know more.

What is the data that is holding the RAM.

why is that varying along with OS , we didn't observe such issue in Centos.

[jo...@cloudamqp.com]

It is probably not the change in OS, but something else. 

You can query the individual queues to (potentially) learn more, along the lines of:

rabbitmqctl eval 'Vhost = <<"vhostnamehere">>, QName = <<"queuenamehere">>, QPid = rabbit_amqqueue:pid_of(Vhost, QName), QInfo = recon:info(QPid), QState = recon:get_state(QPid), io:format("QUEUE INFO:~n~p~n~nQUEUE STATE:~n~p~n", [QInfo, QState]).'

But the main point is to upgrade and to cqv2 and 3.13.x and monitoring: https://www.rabbitmq.com/docs/monitoring

If it happens again then, we can try to reproduce the issue.