[horde] apache cpu usage?

[Michael J Rubinsky]

Quoting Arjen de Korte <arjen+horde at de-korte.org>:

> Citeren avp at rokeyetee.com:
>
>> Quoting Michael J Rubinsky <mrubinsk at horde.org>:
>>
>>> Quoting avp at rokeyetee.com:
>>>
>>>> I'm running Horde on a AWS t2.medium instance - HORDE GROUPWARE WEBMAIL
>>>> EDITION 5.2.6
>>>>
>>>> I've got some funny apache behaviour that just doesn't seem right to
>>>> me...
>>>>
>>>> When I run "apache2ctl status", 99% of the time all threads are in the
>>>> "W"
>>>> (Sending Reply) state:
>>>>
>>>>    Current Time: Thursday, 18-Feb-2016 10:02:53 NST
>>>>    Restart Time: Thursday, 18-Feb-2016 09:49:25 NST
>>>>    Parent Server Config. Generation: 1
>>>>    Parent Server MPM Generation: 0
>>>>    Server uptime: 13 minutes 27 seconds
>>>>    Server load: 0.77 0.77 0.85
>>>>    Total accesses: 1382 - Total Traffic: 7.7 MB
>>>>    CPU Usage: u230.64 s11.47 cu0 cs0 - 30% CPU load
>>>>    1.71 requests/sec - 9.8 kB/second - 5.7 kB/request
>>>>    20 requests currently being processed, 8 idle workers
>>>>  
>>>> _WWWWWW_WWWWW__W_WWWWWW__W.K_...........
>>>>
>>>> It seems strange to me that "sending reply" would be the bottleneck?
>>>>
>>>> Also when I run top, I constantly see apache procs jumping to the top
>>>> with
>>>> up to 50% cpu usage.
>>>>
>>>> Most all the connections are ActiveSync.
>>>
>>> When an ActiveSync client is configured for "Push", the connection to
>>> the webserver remains open while it runs the PING command. These
>>> requests last up to the "hearbeat interval" that is negotiated between
>>> the server and client unless there is a change detected, when the PING
>>> requests ends and a new SYNC request is issued. It makes complete sense
>>> that you would see ActiveSync connections remaining open.
>>
>> Thanks for the quick reply.
>>
>> I'm not questioning that the ActiveSync connections remain open - I  
>> get that.  I'm questioning that the connections are in the "Sending  
>> Reply" state?  And that my CPU usage seems too high to me?  I'm  
>> wondering if there is some php being called to generate the reply  
>> that is being sent but it is taking abnormally long/excessive cpu?   
>> Just sort of guessing here...  How might I track down what is using  
>> the cpu or why the connections are in the sending state?
>>
>> Here are my activesync settings:
>>
>> $conf['activesync']['ping']['heartbeatmin'] = 60;
>> $conf['activesync']['ping']['heartbeatmax'] = 2700;
>> $conf['activesync']['ping']['heartbeatdefault'] = 480;
>> $conf['activesync']['ping']['deviceping'] = true;
>> $conf['activesync']['ping']['waitinterval'] = 10;
>>
>> I just changed waitinterval from 5 to 10.
>
> That is still an awfully short interval. It will mean that the PHP  
> process that is kept active for each device that is connected  
> through ActiveSync will poll the users mailbox every 10 seconds.  
> Depending on the number of users you have, this may constitute a  
> fairly significant load. Note that if you have a decent IMAP server  
> such a short interval is a waste of effort anyway, as the IMAP  
> server will notify that things have changed.

Why is it a waste of effort? It means that the sync client will be  
notified of the email sooner. Also, there is no way for the IMAP  
server to notify the activesync library about any changes OTHER than  
checking it for changes.  If you have a good server with  
MODSEQ/CONDSTORE/QRESYNC support, this is simply a check of the  
HIGHESTMODSEQ value and/or NEXTUID (depending on what we are  
checking). Performance is further improved by using the IMAP cache -  
which may already know about changes.

Not saying that the waitinterval shouldn't be raised, just be aware  
that a value like 60 seconds means it could take up to a full minute  
(possibly longer depending on where in the PING cycle the change  
occurs) before the change is detected and sent to the client.

>> Any suggestions on what these should be?
>
> If you have a significant number of users connected through  
> ActiveSync, increase waitinterval to something like 60 seconds (or  
> more).
>
>> Any other tips/advice to lower CPU usage?
>
> Which IMAP server are you using and how many ActiveSync devices do  
> you have connected?
>
>> Thanks again.
>>
>>>
>>>> What are recommended settings for apache when running Horde?
>>>>
>>>> Any other tips/advice to lower CPU usage?  
>>>> Thanks.
>>>>
>>>>  
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>>>
>>> --
>>> mike
>>> The Horde Project
>>> http://www.horde.org
>>> https://www.facebook.com/hordeprojecthttps://www.twitter.com/hordeproject
>>
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>
>
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-- 
mike
The Horde Project
http://www.horde.org
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