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From Toom Andreas <>
Subject RE: Ajp Nio-thread stuck in loop and consuming a lot of cpu
Date Mon, 22 Jan 2018 07:42:05 GMT
Hi Mark,

Thanks for the info - I think we will focus on migrating to the 8.5.x branch first. If we
experience the same issue on that branch I will restart our investigation and might come back
with additional debugging information to see if we can identify the root cause.

Thanks for your help!

Best regards,
-----Original Message-----
From: Mark Thomas [] 
Sent: den 19 januari 2018 18:46
To: Tomcat Users List <>
Subject: Re: Ajp Nio-thread stuck in loop and consuming a lot of cpu

On 19/01/2018 14:35, Toom Andreas wrote:
> Hi Mark,
> Sorry for the late reply, it has been a couple of busy days.
> We are running our application on two nodes and we have seen the issue on both nodes.
These machines are running quad core cpus. What we have usually seen is that the application
jvm process is consuming 100% (basically one core) on one machine and 200% (2 cores) on the
other machine. The cpu usage/core usage seems to correlate quite well with the number of looping
threads that we can observe via jmx.
> The load does not move between threads, it is pinned to the looping thread.
> We have only observed this behavior on one application and only in production. "Unfortunately"
we did a deployment this week so both nodes have been restarted which means that at the moment
the cpu usage is down to almost 0.
> We are planning to update to Tomcat 8.5.x in the coming week (planned update, not a forced
update related to this issue). Are you aware of any major code changes between the 8.0.x and
8.5.x branches related to this functionality  ?

There is a significant refactoring of the connectors between 8.0.x and 8.5.x to reduce code
duplication, improve consistency of behaviour between the implementations and to support HTTP/2.


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