[sr-dev] MySQL weirdness - timeout does not work

[Daniel-Constantin Mierla]

On 18/05/15 13:31, Klaus Darilion wrote:
>
> On 15.05.2015 22:48, Daniel-Constantin Mierla wrote:
>>
>> On 15/05/15 21:55, Klaus Darilion wrote:
>>> Am 15.05.2015 um 17:54 schrieb Klaus Darilion:
>>>> Hi Daniel!
>>>>
>>>> On 08.05.2015 15:33, Daniel-Constantin Mierla wrote:
>>>>> Hello,
>>>>>
>>>>> On 08/05/15 15:13, Klaus Darilion wrote:
>>>>>> Hi!
>>>>>>
>>>>>> (Kamailio 4.2.2 on Debian Squeeze with libmysqlclient16 5.1.73)
>>>>>>
>>>>>> I have a problem that a lost TCP connection is not detected by
>>>>>> Kamailio/MySQL-CLient and this blocks the Kamailio process for 15
>>>>>> minutes until Linux reports the TCP connection as broken.
>>>>>>
>>>>>> I am using db_mysql with the default settings. Thus, according to the
>>>>>> db_mysql README, the default timeout_interval() of 2 seconds should
>>>>>> be used.
>>>>>>
>>>>>> As this is not the case I took a look at the code and got confused: it
>>>>>> seems there are 2 different mysql modules in modules/db_mysql, eg: the
>>>>>> interface is defined in mysql_mod.c and km_db_mysql.c. Which one is
>>>>>> actually used? I see they have different timeout setting code.
>>>>>>
>>>>>> Any hints on why the timeout is not working?
>>>>> the files starting with km_* are used by kamailio modules. The other
>>>>> are
>>>>> for db api v2, used by few modules inherited from ser (those prefixed
>>>>> with uid_*).
>>>> I checked the code and the timeouts are correctly initialized.
>>>>
>>>> During all my tests Kamailio behaves correct and the lost TCP connection
>>>> is detected after the configured timeout.
>>>>
>>>> But what drives my nuts is: it does not work on my production server. Do
>>>> you have any ideas what could be the case that the timeout is not
>>>> detected?
>>> I think it is related to the debugger module. First tests show that
>>> the mysql timeout works if the debugger module is not loaded. Is there
>>> a known issue, e.g. with signal handlers, when the debugger module is
>>> loaded?
>>>
>> I am not aware of issues and I don't remember debugger module
>> overwriting any signal handler. What parameters do you set for debugger
>> module?
> It seems that I was wrong. After I enabled the debugger module again, it
> still works. Maybe it only worked due to the restart and the problem
> starts only after a certain uptime.
>
> Once I connected with strace to the process which waited for a mysql
> timeout and the timeout did not worked. The strace output was (a few
> times per second):
>
> sigreturn()                             = ? (mask now [])
> read(6, 0xa395f60, 16384)               = -1 EINTR (Interrupted system call)
> --- SIGALRM (Alarm clock) @ 0 (0) ---
> sigreturn()                             = ? (mask now [])
> read(6, 0xa395f60, 16384)               = -1 EINTR (Interrupted system call)
> --- SIGALRM (Alarm clock) @ 0 (0) ---
> sigreturn()                             = ? (mask now [])
> read(6, 0xa395f60, 16384)               = -1 EINTR (Interrupted system call)
> --- SIGALRM (Alarm clock) @ 0 (0) ---
>
> Do you have an idea what that could be related too?
Just a guess now, it might be the non-blocking read inside the
libmysqlclient.

Cheers,
Daniel

-- 
Daniel-Constantin Mierla
http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda
Kamailio World Conference, May 27-29, 2015
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