[horde] Too many httpd processes and no response

[ANANT S ATHAVALE]

  ----- Message from Arjen de Korte <arjen+horde at de-korte.org> ---------
   Date: Tue, 14 Jan 2014 13:49:41 +0100
   From: Arjen de Korte <arjen+horde at de-korte.org>
Subject: ***SPAM-UTM*** Re: [horde] Too many httpd processes and no
response
     To: horde at lists.horde.org

> Citeren ANANT S ATHAVALE <asa at isac.gov.in>:
>
>> ----- Message from Arjen de Korte <arjen+horde at de-korte.org> ---------
>>    Date: Tue, 14 Jan 2014 09:58:43 +0100
>>    From: Arjen de Korte <arjen+horde at de-korte.org>
>> Subject: Re: [horde] Too many httpd processes and no response
>>      To: horde at lists.horde.org
>>
>>> Citeren ANANT S ATHAVALE <asa at isac.gov.in>:
>>>
>>>> ----- Message from Arjen de Korte <arjen+horde at de-korte.org> ---------
>>>>    Date: Mon, 13 Jan 2014 15:52:03 +0100
>>>>    From: Arjen de Korte <arjen+horde at de-korte.org>
>>>> Subject: Re: [horde] Too many httpd processes and no response
>>>>      To: horde at lists.horde.org
>>>>
>>>>> Citeren ANANT S ATHAVALE <asa at isac.gov.in>:
>>>>>
>>>>>> Dear List,
>>>>>>
>>>>>> I have released HGWE 5.1.3 to my users from last 3 days.
>>>>>>
>>>>>> We are facing unusual problem.
>>>>>>
>>>>>> When there is not much load, there is no problem at all.
>>>>>>
>>>>>> But, during peak hours of usage on a working day, suddenly too many
>>>>>> httpd
>>>>>> processes start and user gets no response.  Only solution is to
>>>>>> restart
>>>>>> httpd.  By this, there won't any issue for atleast one hour and
>>>>>> problem
>>>>>> repeats.
>>>>>
>>>>> My first guess would be that you allow your server to spawn too many
>>>>> processes to serve the incoming requests. If this is more than the
>>>>> amount of memory allows, the result will be swapping and a dramatic
>>>>> decrease in performance. Users will try to reconnect then, worsening
>>>>> the
>>>>> problem. Which webserver are you using? If Apache, which MPM are you
>>>>> using?
>>>>
>>>> Using Apache.  prefork MPM.  Default, as provided by RHEL.
>>>
>>> What is the average process size of Apache? You may need to change
>>> 'httpd' in the below to whatever RHEL is using:
>>>
>>> ps -ylC httpd | awk '{x += $8;y += 1} END {print "Apache Memory Usage
>>> (MB): "x/1024; print "Average Proccess Size (MB): "x/((y-1)*1024)}'
>>
>> This is what I got on a minimal load condition. 
>> Apache Memory Usage (MB): 1651.5
>> Average Process Size (MB): 63.5191
>
> That's a process size about what I would expect for a system running
> Horde. You'll want to keep an eye on these figures when the load is
> higher too.
>
> OK.
>
>>> Make sure that the server is actually under load, to make sure the
>>> process sizes reported are representative. If the average process size
>>> multiplied by the value of MaxClients in your apache configuration is
>>> more than about 75-80% of the memory in the system, you're just waiting
>>> for a disaster to happen sooner or later.
>>
>> As per this, I should not have MaxClients somewhere around 400 or even
>> lesser.  Please correct me, if I am wrong.
>
> Assuming that the amount of free memory (without Apache running) would
> be about 24 GB (allowing for some additional memory for other
> applications), MaxClients should definitly not be higher than about 400.
>
> OK
>
>>> How many concurrent users do you expect to use Horde?
>>
>> I don't know, how to get concurrent users.  But, as soon as, office
>> hours start, at least 500 to 600 users will login.
>
> That should be manageable with MaxClients equal to 400 (and even quite a
> bit lower too), provided KeepAliveTimeout is set to a small enough
> number (not more than the default of 5 seconds, 2 seconds is better on a
> busy server).
>
> In our config of RHEL, default is 15 seconds.  I am changing it to 5
> seconds as suggested.
>
> What you should also check, is if under load the database (or IMAP)
> performance is not the limiting factor. If the database (or IMAP) is
> slow, the requests to Horde will take longer to complete and hence, the
> number of httpd processes will increase. There is nothing Apache or
> Horde can do about that.
>
> OK.
>
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----- End message from Arjen de Korte <arjen+horde at de-korte.org> -----

Thank you for sharing your valuable guidance.  I Will keep you and list
updated.
-- 
           Regards
            Anant
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