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From:Reindl Harald Date:March 29 2012 5:33pm
Subject:Re: mysqld got signal 6 (problem why bigger than I initially realised)
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Am 29.03.2012 19:20, schrieb Rick James:
> I'll disagree with your disagreement.
> 
> Many web servers maintain persistent connections.  

this is a stupid idea for most workloads
i thought we are speaking about useful configured servers

persistent connections will not work on machines with
many websites / db-users, you describe the result of
using them - they are only useful on dedicated servers
with only one db-user

> This leads to eventually exceeding max_connections, even if
> connections are rare.  Once he hits 41, he will be issuing 404s, or other bad stuff.

that is why you have to find out a typical workload

my software is using a self written db-abstraction which
will try again if connect fails up to 10 times

this does usually not happen often

> Also, having 1000 http threads hanging around is a waste when you rarely have 10
> active at once.  Or do your
> threads somehow take a long time without taking much in resources (CPU, I/O, MySQL,
> etc)?  If each of 1000 threads
> took only 1% of the CPU, the CPU would be overloaded, even on an 8-core box.

what exactly did you not understadn in my last paragraph?

>> however - 1000 is much too high if we are speak
>> about a preforked server on most hardware - keep
>> in mind that a worker process with mod_php consumes
>> some MB of memory in a typical environment

with enough memory even this would be possible

i had a prjoect last year with 400 active httpd-workers
on a high dynamic webpage on a virtaul machine while
the host serves 10 other different guests with a mixed
workload of some webservers with > 500 domains, mail,
spamfirewall and vpn-gateway and the host did never get
higher than 70% CPU

ok, all the 500 domains are using a highly optimized
CMS which was inhouse developed and is maintained and
optimized since 10 years, but you see the workload
is possible without problems

> On 3/27/12 10:38 PM, Reindl Harald wrote:
>>
>> Am 27.03.2012 23:24, schrieb Rick James:
>>> MaxClients          1000
>>> could overwhelm  max_connections = 41 .  Strongly recommend you decrease
>>> MaxClients to less than max_connections
>>> (not the other way around).
>> totally wrong!
>>
>> not every http-connection implies a myql-connection
>> a website typically contains a lot of static files
>> like images, javascripts, stylesheets and you bring
>> down your httpd if MaxClients is set too low and
>> you are unable to serve waiting clients
>>
>> additionally if KeepAlive is used there are open
>> httpd-connections with NO db-connection after
>> serving a dynamic page using one out of MaxClients
>> for a timewindow based on KeepAliveTimeout
>>
>> MaxClients on httpd should never be lower than "max_connections"
>> "max_connections" is primary a question of RAM and typical load
>>
>> mysqltuner.pl:
>> [--] Total buffers: 2.4G global + 3.2M per thread (200 max threads)
>> [OK] Maximum possible memory usage: 3.0G (37% of installed RAM)
>> _____________________
>>
>> however - 1000 is much too high if we are speak
>> about a preforked server on most hardware - keep
>> in mind that a worker process with mod_php consumes
>> some MB of memory in a typical environment
>>
>> but this is all not mysql related
>>
> 

-- 

Mit besten Grüßen, Reindl Harald
the lounge interactive design GmbH
A-1060 Vienna, Hofmühlgasse 17
CTO / software-development / cms-solutions
p: +43 (1) 595 3999 33, m: +43 (676) 40 221 40
icq: 154546673, http://www.thelounge.net/

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Thread
mysqld got signal 6 (problem why bigger than I initially realised)Brent Clark27 Mar
  • Re: mysqld got signal 6 (problem why bigger than I initially realised)P.R.Karthik27 Mar
    • Re: mysqld got signal 6 (problem why bigger than I initially realised)Brent Clark27 Mar
      • Re: mysqld got signal 6 (problem why bigger than I initially realised)Rick James27 Mar
        • Re: mysqld got signal 6 (problem why bigger than I initially realised)Brent Clark27 Mar
          • Re: mysqld got signal 6 (problem why bigger than I initially realised)Rick James27 Mar
            • Re: mysqld got signal 6 (problem why bigger than I initially realised)Reindl Harald28 Mar
              • Re: mysqld got signal 6 (problem why bigger than I initially realised)Rick James29 Mar
                • Re: mysqld got signal 6 (problem why bigger than I initially realised)Reindl Harald29 Mar