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From Honza Lefty Škoda <le...@multihost.cz>
Subject Re: [users@httpd] mod_fcgid ignoring both scores and process count
Date Mon, 22 Nov 2010 16:52:28 GMT
On 22.11.2010 02:55, Jeff Trawick wrote::
> 2010/11/21 Jeff Trawick <trawick@gmail.com>:
>> 2010/11/21 Honza Lefty Škoda <lefty@multihost.cz>:
>>> On 21.11.2010 16:57, Jeff Trawick wrote::
>>>> 2010/11/21 Honza Lefty Škoda <lefty@multihost.cz>:
>>>>> I am running performance benchmarks with ab2 on my server and I
>>>>> discovered that fcgid creates much more than FcgidMaxProcessesPerClass.
>>>>> And if I make 15 concurrent requests fcgi starts 15 php processes at
the
>>>>> same time without worrying about FcgidSpawnScoreUpLimit!
>>>>>
>>>>> I use mod_fcgid with suexec for php execution (via php-wrapper bash
>>>>> script, which does a lot of magic including execs, chroot and setuid).
>>>>>
>>>>> The configuration (for fcgid 2.3.6 on apache 2.2.15):
>>>>>
>>>>> /etc/apache2/modules.d/20_mod_fcgid.conf:
>>>>> 25: FcgidMinProcessesPerClass 0
>>>>> 26: FcgidMaxProcessesPerClass 10
>>>>>
>>>>> 33: FcgidSpawnScore 10
>>>>> 34: FcgidTerminationScore 20
>>>>> 35: FcgidTimeScore 1
>>>>> 36: FcgidSpawnScoreUpLimit 25
>>>>
>>>> I did find/fix one related issue this a.m.:  the first process created
>>>> didn't adjust the score, so you could in effect create one more
>>>> process than desired during ramp-up.  I didn't see your exact issue
>>>> though.
>>>>
>>>> Two things:
>>>>
>>>> Does your "magic" wrapper logic preserve the pid created by mod_fcgid
>>>> (i.e., use exec instead of fork)?  If not, the fcgid PM will be
>>>> confused and you're probably getting requests successfully processed
>>>> between the time fcgid forks a child and when it exits.  (That
>>>> probably isn't a workable explanation since an exiting child would add
>>>> a huge number -- 20 -- to the score.  But please confirm anyway :) )
>>> Yes, PID of php-cgi process matches the one in server-status worker list.
>>>
>>>>
>>>> If you are preserving the pid (i.e., fcgid PM can track what it has
>>>> created), turn on LogLevel info and see if you can get more insight
>>>> into what is happening with spawn score manipulation/checking.  Here's
>>>> what I get using the directives you posted and hammering on one script
>>>> with ab (>100 current clients):
>>>
>>> Good idea!
>>> I tried to run the tests again with surprising results. Some
>>> VirtualHosts break rules:
>>>
>>> Sun Nov 21 16:57:33 2010] [info] mod_fcgid: server
>>> *:/opt/hostik/webbin/php-wrapper.fcgi(11473) started
>>> [Sun Nov 21 16:57:33 2010] [info] mod_fcgid: server
>>> *:/opt/hostik/webbin/php-wrapper.fcgi(11474) started
>>> [Sun Nov 21 16:57:33 2010] [info] mod_fcgid: server
>>> *:/opt/hostik/webbin/php-wrapper.fcgi(11475) started
>> ...
>>>
>>> After several benchmarks I found out that it's caused by the
>>> FcgidMinProcessesPerClass which is set to 1 for some vhosts. When I set
>>> this, scores are completely ignored!
>>
>> Thanks for finding that; I've now duplicated it.  Hopefully it will be
>> easy to resolve.  (It acts like a classic merging bug, but the score
>> configurations are supposed to be taken from the main vhost so merging
>> is supposed to be irrelevant.)
>>
> 
> this fixes it for me:
> 
> Index: modules/fcgid/fcgid_spawn_ctl.c
> ===================================================================
> --- modules/fcgid/fcgid_spawn_ctl.c     (revision 1037483)
> +++ modules/fcgid/fcgid_spawn_ctl.c     (working copy)
> @@ -178,7 +178,7 @@
>          if (current_node->inode == command->inode
>              && current_node->deviceid == command->deviceid
>              && !strcmp(current_node->cmdline, command->cmdline)
> -            && current_node->vhost_id == sconf->vhost_id
> +            && current_node->vhost_id == command->vhost_id
>              && current_node->uid == command->uid
>              && current_node->gid == command->gid)
>              break;
> 

Works great! Now I am facing another score related issue - on gracefull
reload, the scores are kept, but the processes are killed (which results
in really high scores). After that, no fcgi processes are spawned for
quite a long time. It would be wise to reset scores. And as I don't know
any other (more official) way to submit bugs, I write it here again. :)

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