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From André Warnier (tomcat)>
Subject Re: 21 second pause that randomly happens
Date Mon, 16 Jul 2018 14:59:57 GMT
On 16.07.2018 16:35, David Cleary wrote:
> 2018-07-16 15:55 GMT+03:00 David Cleary <>:
>>> We have a customer who is experiencing a random, 21 second pause when using out
> based application server. We believe this may be during a TCP connect and timeout. Logging
> indicates the pause happens before the request makes it to our back end.

Logging where then ?

  It mostly happens
> when we create an initial logical connection, but we have also seen it elsewhere where
> believe the TCP Keep alive was expired and a new socket had to be established. However,
> do not know this and am hoping there is some logging I can turn on in the NIO connector
> collect more data. I tried turning on logging in the Endpoint class, but that did not
> anything useful.

If the connection request does not even reach the Tomcat back-end, that is also unlikely 
to provide much information. (Not being facetious here, just stating a fact).
Can you do a "netstat" command on your Tomcat server when this happens ?
If yes, maybe some part of the output would provide some information from the TCP level 
(such as a high number of connections, to the Tomcat NIO port, in some specific TCP state


  There is a NAT firewall between the client and server, so I'm looking for
> some TCP level logging that could point me in the proper direction.
>> Tomcat version = ?
> Sorry. Tomcat 8.5.27.

And on which kind of O.S. is this happening ?

Also maybe another question : is this happening on a Tomcat server which is dedicated to 
that particular customer ? or is the Tomcat server shared between different customers, and

only that particular customer experiences these delays ?

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