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

[Nishant Kumar]

I have tried XNIO 3.7.7-Final  with jboss.threads 2.3.3.Final in
Undertow 2.0.30.Final
and it looks good so far. I am running it in production for the last 2 days
and no issues so far :). I am monitoring it and will report if find
anything.

The reason I changed jboss thread version is that I observed a high CPU
load in XNIO 3.7.7.Final comparing XNIO 3.3.8.Final which I reported in the
last email. However, I have not done any extensive tests for it.

On Thu, Mar 12, 2020 at 1:37 PM Nishant Kumar <nishantkumar35 at gmail.com>
wrote:

> I have also observed that the CPU load increases significantly on
> 3.7.7-Final (load average 50 on 48 core machine) on moderate load but it's
> very low (load average 20) on 3.3.8-Final on the same QPS (20k Req/sec) and
> it (3.7.7-Final) starts refusing connection on high load.
>
> On Thu, Mar 12, 2020 at 7:20 AM Nishant Kumar <nishantkumar35 at gmail.com>
> wrote:
>
>> 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>
>>>
>>
>
> --
> Nishant Kumar
> Bangalore, India
> Mob: +91 80088 42030
> Email: nishantkumar35 at gmail.com
>


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