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

[Stuart Douglas]

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
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