[Mono-dev] WebRequest timeouts after ThreadPool exhaustion

Fri Feb 12 14:07:31 UTC 2016

I tried the testcase on master and couldn't reproduce there. I could,
however, reproduce it on the 4.3.2 build I had installed
(mono-4.3.2-branch/0df254d). I'm downloading a later 4.3.2 build right now
to see if it still happens there, if it does then we need to backport
something from master.

- Alex

2016-02-12 15:04 GMT+01:00 Seif Attar <iam at seifattar.net>:

> Great, I'll try it out. Is the console app in that gist enough for a test
> case?
>
> @Mike @Jonathan we've faced bugs with previous versions of libc and
> networking before, also some kernel issues. Update to latest if you can. I
> can't reproduce with 3.12. I get timeouts but then it recovers when there
> are available threads unlike with 4.x
>
> On Fri, 12 Feb 2016 13:50 Alan <alan.mcgovern at gmail.com> wrote:
>
>> It's also worth pointing out that the threadpool implementation has
>> changed completely since mono 4.0. I believe the new threadpool
>> implementation shipped as the default starting with mono 4.2 (or
>> thereabouts). If you're on older Monos the odds are high whatever issue you
>> have has been fixed already.
>>
>> Alan
>>
>> On 12 February 2016 at 13:48, Alan <alan.mcgovern at gmail.com> wrote:
>>
>>> Hey,
>>>
>>> We have just fixed some issues in that area. They are expected to ship
>>> as part of a the next mono 4.3+ release. If you want to test them out in
>>> the meantime you could try building mono with this PR [0] and see if it
>>> resolves all your issues. If it doesn't then a testcase and bug report on
>>> http://bugzilla.xamarin.com would be awesome!
>>>
>>> Thanks!
>>>
>>> [0] https://github.com/mono/mono/pull/2576
>>>
>>> On 12 February 2016 at 12:33, Mike Horsley <mhorsley at vqcomms.com> wrote:
>>>
>>>> we’ve also seen instances of webrequest timeouts that don’t recover
>>>> (but curl worked) as well but haven’t got to the bottom of it yet.
>>>>
>>>>
>>>>
>>>> we ran your test app and see the same issue with mono 3.12 on OpenSUSE
>>>> 13.2 (kernel 3.16.7, libc 2.19).
>>>>
>>>>
>>>>
>>>> we’ll add the diagnostics from your test app into ours and this will
>>>> tell us whether we are seeing the same issue with the threadpool.
>>>>
>>>>
>>>>
>>>> regards
>>>>
>>>> Mike
>>>>
>>>>
>>>>
>>>> *From:* mono-devel-list-bounces at lists.ximian.com [mailto:
>>>> mono-devel-list-bounces at lists.ximian.com] *On Behalf Of *Seif Attar
>>>> *Sent:* Friday, February 12, 2016 10:43 AM
>>>> *To:* mono-devel-list at lists.ximian.com
>>>> *Subject:* [Mono-dev] WebRequest timeouts after ThreadPool exhaustion
>>>>
>>>>
>>>>
>>>> Hi,
>>>>
>>>> We are running mono 4.2.2 in prod and the VM that the process was
>>>> running on had SAN failure and after storage recovered, all outgoing
>>>> requests were timing out, even though doing a curl was working fine.
>>>>
>>>> Theory was that thread pool starved and somehow things didn't recover
>>>> properly.
>>>>
>>>> Managed to reproduce with:
>>>>
>>>>
>>>> https://gist.githubusercontent.com/seif/ae2defbfa5afa26fa8f6/raw/bef351eded56c882658a4bad60fa4818ad32d629/timeout.cs
>>>>
>>>> Even after ThreadPool finishes the tasks and has available threads, it
>>>> never recovers and subsequent webrequests all timeout.
>>>>
>>>> Running on mono 4.2.2, linux kernel 4.2.0-27 and libc 2.21.
>>>>
>>>> Output from gdb is:
>>>>
>>>> (gdb) info threads
>>>>   Id   Target Id         Frame
>>>>   13   Thread 0x7fca903ff700 (LWP 27944) "cli" pthread_cond_wait@@GLIBC_2.3.2
>>>> () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
>>>>   12   Thread 0x7fca90b34700 (LWP 27945) "Finalizer" 0x00007fca911d70c9
>>>> in futex_abstimed_wait (cancel=true, private=<optimised out>, abstime=0x0,
>>>> expected=0, futex=0x948ae0) at sem_waitcommon.c:42
>>>>   11   Thread 0x7fca8dfff700 (LWP 27946) "Timer-Scheduler"
>>>> pthread_cond_timedwait@@GLIBC_2.3.2 () at
>>>> ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
>>>>   10   Thread 0x7fca91ba1700 (LWP 27947) "cli" __clock_nanosleep
>>>> (clock_id=1, flags=1, req=0x7fca91ba0dc0, rem=0x7fca90f134aa
>>>> <__clock_nanosleep+138>) at ../sysdeps/unix/sysv/linux/clock_nanosleep.c:48
>>>>   9    Thread 0x7fca8ddfe700 (LWP 27948) "Threadpool work"
>>>> pthread_cond_timedwait@@GLIBC_2.3.2 () at
>>>> ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
>>>>   8    Thread 0x7fca8dbfd700 (LWP 27949) "Threadpool work"
>>>> pthread_cond_timedwait@@GLIBC_2.3.2 () at
>>>> ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
>>>>   7    Thread 0x7fca8d7fb700 (LWP 27951) "Threadpool work"
>>>> pthread_cond_timedwait@@GLIBC_2.3.2 () at
>>>> ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
>>>>   6    Thread 0x7fca8d3f9700 (LWP 27953) "Threadpool work"
>>>> pthread_cond_timedwait@@GLIBC_2.3.2 () at
>>>> ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
>>>>   5    Thread 0x7fca8d1f8700 (LWP 27954) "Threadpool work"
>>>> pthread_cond_timedwait@@GLIBC_2.3.2 () at
>>>> ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
>>>>   4    Thread 0x7fca8cff7700 (LWP 27955) "Threadpool work"
>>>> pthread_cond_timedwait@@GLIBC_2.3.2 () at
>>>> ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
>>>>   3    Thread 0x7fca8cdf6700 (LWP 27956) "Threadpool work"
>>>> pthread_cond_timedwait@@GLIBC_2.3.2 () at
>>>> ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
>>>>   2    Thread 0x7fca8cbf5700 (LWP 27957) "Threadpool work"
>>>> pthread_cond_timedwait@@GLIBC_2.3.2 () at
>>>> ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
>>>> * 1    Thread 0x7fca91cf0780 (LWP 27942) "cli" 0x00007fca911d7e0d in
>>>> read () at ../sysdeps/unix/syscall-template.S:81
>>>>
>>>> Could not reproduce on mono 3.12, but it happens on 4.0.3 and 4.2.2
>>>>
>>>> Is this a known issue? any workarounds? Tried setting MONO_DNS=1 to use
>>>> the clr dns, but that didn't help.
>>>>
>>>> Let me know if there is any more info I need to provide.
>>>>
>>>> Thanks,
>>>>
>>>> Seif
>>>>
>>>> _______________________________________________
>>>> Mono-devel-list mailing list
>>>> Mono-devel-list at lists.ximian.com
>>>> http://lists.ximian.com/mailman/listinfo/mono-devel-list
>>>>
>>>>
>>>
>>
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