[users@httpd] Re: mod_fcgid random freeze

[kr...@cflinux.hu]

Dear users,

Finally, I think I've found the problem. On freebsd, devel/apr1 chooses 
apr lock method as flock. Thus,
a file is used for synchronization purposes. mod_fcgid creates a 
temporary file in fcgid_mutex_create() using tmpnam(), which effectively 
creates a temporary file in /tmp. And in my freebsd setup, I've enabled 
/tmp cleaning as well, which removes the lock files after a fix amount 
of time. As apache/apr only opens the file for writing, but actually not 
writing anything to it, the files {a,c,m}time parameters dont change, so 
the /tmp cleaning process cannot detect if the files are still in use, 
it simply removes them.

Either mod_fcgid should use a file located elsewhere, or be 
configurable, or maybe apr could choose another lock method on freebsd. 
As on a gnu system, it chooses systemv semaphores, as I've noticed.

Please comment my investigation.

Regards,


2013-11-04 18:08 időpontban Richard Kojedzinszky ezt írta:
> Dear Users,
> 
> I am having issues when installing mod_fcgid under freebsd. I have
> installed www/apache22 from ports, as well as www/mod_fcgid. After
> some days of running, many of this error message appeared in
> httpd-error.log:
> 
> [Sat Nov 02 09:49:28 2013] [emerg] (2)No such file or directory:
> mod_fcgid: apr_global_mutex_child_init error
> 
> And after hours passed, the entire httpd process stopped working. Only
> two httpd processes left running, but they were not accepting
> connections. I had to restart apache, then it worked again.
> 
> I am using prefork mpm, and have set MaxRequestsPerChild to a non-zero 
> value.
> 
> Unfortunately, right now I cannot reproduce the problem, unfortunately
> it arises randomly.
> 
> Because I did not find any useful regarding this on the web, I am
> requesting help here. What could I do to investigate the problem?
> 
> Thanks in advance,
> Kojedzinszky Richard

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Re: [users@httpd] Re: mod_fcgid random freeze

[Jeff Trawick <tr...@gmail.com>]

On Sat, Nov 16, 2013 at 8:37 AM, <kr...@cflinux.hu> wrote:

> Dear users,
>
> Finally, I think I've found the problem. On freebsd, devel/apr1 chooses
> apr lock method as flock. Thus,
> a file is used for synchronization purposes. mod_fcgid creates a temporary
> file in fcgid_mutex_create() using tmpnam(), which effectively creates a
> temporary file in /tmp. And in my freebsd setup, I've enabled /tmp cleaning
> as well, which removes the lock files after a fix amount of time. As
> apache/apr only opens the file for writing, but actually not writing
> anything to it, the files {a,c,m}time parameters dont change, so the /tmp
> cleaning process cannot detect if the files are still in use, it simply
> removes them.
>
> Either mod_fcgid should use a file located elsewhere, or be configurable,
> or maybe apr could choose another lock method on freebsd. As on a gnu
> system, it chooses systemv semaphores, as I've noticed.
>
> Please comment my investigation.
>

* Good investigation!
* There is good configurability of this mutex (and anything in bundled
httpd modules) using the Mutex directive if you use mod_fcgid with httpd
2.4.
* Perhaps "/tmp cleaning" is broken if it removes files that processes are
holding open.  Try following that thread.
* As you probably already found, you can patch fcgid_mutex_unix.c to change
"apr_lockmech_e mechanism = APR_LOCK_DEFAULT;" to set it to some other
mutex type (see
http://apr.apache.org/docs/apr/1.4/group__apr__proc__mutex.html; probably
not all of the choices will work).
** Maybe the FreeBSD package maintainer would find that appropriate.
* You can file a bug at http://issues.apache.org/bugzilla/.  I'm not aware
of other people reporting mutex problems, so personally I'm not sure it is
justified to make mod_fcgid's mutex configurable with httpd 2.2, except
perhaps with a compile-time definition.
** But other developers may have a different opinion, so file the bug.


> Regards,
>
>
> 2013-11-04 18:08 időpontban Richard Kojedzinszky ezt írta:
>
>  Dear Users,
>>
>> I am having issues when installing mod_fcgid under freebsd. I have
>> installed www/apache22 from ports, as well as www/mod_fcgid. After
>> some days of running, many of this error message appeared in
>> httpd-error.log:
>>
>> [Sat Nov 02 09:49:28 2013] [emerg] (2)No such file or directory:
>> mod_fcgid: apr_global_mutex_child_init error
>>
>> And after hours passed, the entire httpd process stopped working. Only
>> two httpd processes left running, but they were not accepting
>> connections. I had to restart apache, then it worked again.
>>
>> I am using prefork mpm, and have set MaxRequestsPerChild to a non-zero
>> value.
>>
>> Unfortunately, right now I cannot reproduce the problem, unfortunately
>> it arises randomly.
>>
>> Because I did not find any useful regarding this on the web, I am
>> requesting help here. What could I do to investigate the problem?
>>
>> Thanks in advance,
>> Kojedzinszky Richard
>>
>
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