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

[Nishant Kumar]

I didn't get time to write standalone program to reproduce it but with new
version 3.7.7-Final, i am not able to survive for more than an hour. With
the older default xnio version of Undertow (xnio 3.3.8-Final) i can run
server for few days until it stops working with error i mentioned in first
email.

Just FYI, i am using OpenJDK 11 with OpenJ9 JVM.

On Wed, Mar 4, 2020, 10:54 AM Flavia Rainone <frainone at redhat.com> wrote:

> Can someone provide a reproducer for this error?
>
> As for the old version of XNIO, it will be upgraded in Undertow
> 2.1.0.Final.
>
> On Mon, Mar 2, 2020 at 8:47 PM Stuart Douglas <sdouglas at redhat.com> wrote:
>
>> Hmm, maybe this is a bug in the HTTP/2 close code then, and somehow the
>> connection is not being closed if the client hangs up abruptly. I had a
>> quick look at the code though and I think it looks ok, but maybe some more
>> investigation is needed.
>>
>> Stuart
>>
>> On Tue, 3 Mar 2020 at 03:41, Nishant Kumar <nishantkumar35 at gmail.com>
>> wrote:
>>
>>> Yes, i have no control on client side. I am using HTTP2. I have tried
>>> increasing open file limit to 400k but that consumes all memory and system
>>> hangs. I will probably try to put a nginx in front of Undertow and test.
>>>
>>> setServerOption(UndertowOptions.ENABLE_HTTP2, true)
>>>
>>> On Mon, Mar 2, 2020, 7:48 PM David Lloyd <david.lloyd at redhat.com> wrote:
>>>
>>>> On Mon, Mar 2, 2020 at 7:56 AM Stan Rosenberg <stan.rosenberg at acm.org>
>>>> wrote:
>>>> >
>>>> > Stuck in CLOSE_WAIT is a symptom of the client-side not properly
>>>> shutting down [1].
>>>>
>>>> I would partially disagree.  In the article you linked: "It all starts
>>>> with a listening application that leaks sockets and forgets to call
>>>> close(). This kind of bug does happen in complex applications."  This
>>>> seems to be essentially what's happening here: the server isn't
>>>> completing the connection (for some reason), stranding the socket in
>>>> `CLOSE_WAIT`.
>>>>
>>>> We can't assume that the client is abandoning the connection after
>>>> `FIN_WAIT2` (the titular RFC violation); if the server stays in
>>>> `CLOSE_WAIT`, then even if the client dutifully stays in `FIN_WAIT2`
>>>> forever, the resolving condition still needs to be that the server
>>>> shuts down its side of the connection.
>>>>
>>>> This diagram is a useful visual aid, mapping TCP states to the XNIO
>>>> API:
>>>> https://www.lucidchart.com/publicSegments/view/524ec20a-5c40-4fd0-8bde-0a1c0a0046e1/image.png
>>>>
>>>> --
>>>> - DML
>>>>
>>>> _______________________________________________
>> undertow-dev mailing list
>> undertow-dev at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/undertow-dev
>
>
>
> --
>
> Flavia Rainone
>
> Principal Software Engineer
>
> Red Hat <https://www.redhat.com>
>
> frainone at redhat.com
> <https://www.redhat.com>
>
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