[undertow-dev] Too many open files: Exception accepting request, closing server channel TCP server (NIO)

[Nishant Kumar]

Generally, clients also close the connection after a few thousand requests
other than normal fatal conditions. There might be other cases too but I am
not aware of it. They keep initiating new connections if we are not
responding within the threshold time frame. This is a server to server
communication system.

On Mon, Mar 2, 2020 at 10:26 AM Stuart Douglas <sdouglas at redhat.com> wrote:

> This sounds like a bug, when the client closes the connection it should
> wake up the read listener, which will read -1 and then cleanly close the
> socket.
>
> Are the clients closing idle connections or connections processing a
> request?
>
> Stuart
>
> On Mon, 2 Mar 2020 at 14:31, Nishant Kumar <nishantkumar35 at gmail.com>
> wrote:
>
>> I agree that it's a load-balancing issue but we can't do much about it at
>> this moment.
>>
>> I still see issues after using the latest XNIO (3.7.7) with Undertow.
>> what I have observed it that when there is a spike in request
>> and CONNECTION_HIGH_WATER is reached, the server stops accepting new
>> connection as expected and the client starts to close the connection
>> because of delay (we have strict low latency requirement < 100ms) and try
>> to create new connection again (which will also not be accepted) but server
>> has not closed those connections (NO_REQUEST_TIMEOUT = 6000) and there will
>> be high number of CLOSE_WAIT connections at this moment. The server is
>> considering CLOSE_WAIT + ESTABLISHED for CONNECTION_HIGH_WATER (my
>> understanding).
>>
>> Is there a way that I can close all  CLOSE_WAIT connection at this moment
>> so that connection counts drop under CONNECTION_HIGH_WATER and we start
>> responding to newly established connections? or any other suggestions? I
>> have tried removing CONNECTION_HIGH_WATER and relying on the FD limit but
>> that didn't work.
>>
>> On Sun, Mar 1, 2020 at 7:47 AM Stan Rosenberg <stan.rosenberg at gmail.com>
>> wrote:
>>
>>> On Sat, Feb 29, 2020 at 8:18 PM Nishant Kumar <nishantkumar35 at gmail.com>
>>> wrote:
>>>
>>>> Thanks for the reply. I am running it under supervisord and i have
>>>> updated open file limit in supervisord config. The problem seems to be same
>>>> as what @Carter has mentioned. It happens mostly during sudden traffic
>>>> spike and then sudden increase (~30k-300k) of TIME_WAIT socket.
>>>>
>>>
>>> The changes in
>>> https://github.com/xnio/xnio/pull/206/files#diff-23a6a7997705ea72e4016c11bf9d214bR453 are
>>> likely to improve the exceptional case of exceeding the file descriptor
>>> limit. However, if you're already setting the limit too high (e.g., in our
>>> case it was 795588), then exceeding it is a symptom of not properly
>>> load-balancing your traffic; with that many connections, you'd better have
>>> a ton of free RAM available.
>>>
>>
>>
>> --
>> Nishant Kumar
>> Bangalore, India
>> Mob: +91 80088 42030
>> Email: nishantkumar35 at gmail.com
>> _______________________________________________
>> undertow-dev mailing list
>> undertow-dev at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/undertow-dev
>
>

-- 
Nishant Kumar
Bangalore, India
Mob: +91 80088 42030
Email: nishantkumar35 at gmail.com
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