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

[Stuart Douglas]

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
>>
>>
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