[asterisk-bugs] [JIRA] (ASTERISK-23719) Asterisk locks, UDP buffer overflow, 1000+ spawns of 'chan_iax2.c find_idle_thread()'

[Rusty Newton (JIRA)]

     [ https://issues.asterisk.org/jira/browse/ASTERISK-23719?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Rusty Newton updated ASTERISK-23719:
------------------------------------

    Assignee: SteelPivot  (was: Rusty Newton)
      Status: Waiting for Feedback  (was: Triage)

> Asterisk locks, UDP buffer overflow, 1000+ spawns of 'chan_iax2.c find_idle_thread()'
> -------------------------------------------------------------------------------------
>
>                 Key: ASTERISK-23719
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-23719
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Channels/chan_iax2
>    Affects Versions: 11.6.1
>         Environment: CentOS 6.4min
>            Reporter: SteelPivot
>            Assignee: SteelPivot
>            Severity: Critical
>         Attachments: 1399319401-core-show-locks.txt, 1399324201-backtrace-threads.txt, 1399324201-core-show-threads.txt, 1399324201-netstat.txt, 1399750801-backtrace-threads.txt, 1399750801-core-show-taskprocessors.txt, 1399750801-core-show-threads.txt, 1399750801-netstat.txt, 1400606323-backtrace-threads.txt, 1400606323-client-iax2-debug.txt, 1400606323-client-iax2.pcap, 1400606323-core-show-taskprocessors.txt, 1400606323-core-show-threads.txt, 1400606323-host-iax2-debug.txt, 1400606323-host-iax2.pcap, 1400606323-netstat.txt
>
>
> We've been experience an issue for a few months concerning IAX2 peers which has recently gotten more severe after upgrading from 11.2 to 11.6cert2.
> The initial symptom was all (100+) IAX2 peers going UNREACHABLE. However, after inspecting further it seems that what will happen is the UDP queues will sharply increase (seen by netstat -antup), the number of asterisk threads increases (to over 1000 threads in some cases), and Asterisk, of course, stops responding to inbound/outbound calls from any channel (SIP or IAX2).
> After recompiling with DEBUG_THREADS and BETTER_BACKTRACES, I discovered that issuing a "gdb -ex "thread apply all bt"...(etc) " to grab a backtrace will free up the UDP queues, and Asterisk will then become responsive again. Currently I have a script running each 5 minutes that pulls the UDP queues for asterisk processes, and upon seeing a queue above 300,000packets, I issue a "netstat -antup", "core show locks", "core show threads", and "gdb -ex "thread apply all bt" --batch asterisk `pidof asterisk` > $debugdir/$date-backtrace-threads.txt".
> I have previously increased the kernel UDP maximums in sysctl.conf, and added options for iaxthreadcount/iaxmaxthreadcount in iax.conf.
> I cannot repeat this issue at will, but it happens every hour or so (sometimes every few minutes). I have debug logs and backtraces for each occurrence.



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