Lucas Tétreault created AMQ-9107:
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Summary: Closing many consumers causes CPU to spike to 100%
Key: AMQ-9107
URL: https://issues.apache.org/jira/browse/AMQ-9107
Project: ActiveMQ
Issue Type: Bug
Reporter: Lucas Tétreault
Attachments: example.zip, image-2022-10-07-00-12-39-657.png,
image-2022-10-07-00-17-30-657.png
When there are many consumers (~188k) on a queue, closing them is incredibly
expensive and causes the CPU to spike to 100% while the consumers are closed.
Tested on an Amazon MQ mq.m5.large instance (2 vcpu, 8gb memory).
I have attached a minimal recreation of the issue where the following happens:
1/ Open 100 connections.
2/ Create consumers as fast as we can on all of those connections until we hit
at least 188k consumers.
3/ Sleep for 5 minutes so we can observe the CPU come back down after opening
all those connections.
4/ Start closing consumers as fast as we can.
5/ After all consumers are closed, sleep for 5 minutes to observe the CPU come
back down after closing all the connections.
In this example it seems 5 minutes wasn't actually sufficient time for the CPU
to come back down and the consumer count and cpu utilization seem to hit 0 at
the same time:
!image-2022-10-07-00-12-39-657.png|width=757,height=353!
In a previous test with more time sleeping after closing all the consumers we
can see the CPU come back down before we close the connections.
!image-2022-10-07-00-17-30-657.png|width=983,height=448!
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