What heresy is present? One uses the tools to do a job. If the open source 
tools aren't up to the job, one goes to all other sources of course.  

On Oct 30, 2012, at 6:28 PM, George Herbert wrote:

> 
> 
> 
> 
> On Oct 30, 2012, at 12:12 PM, David Gerard <[email protected]> wrote:
> 
>> On 29 October 2012 23:56, Dave Humphrey <[email protected]> wrote:
>> 
>>> As a rough guess at what to set MaxClients to use "top" and look at the
>>> difference between the RES and SHR columns of all httpd processes. I
>>> believe this is roughly the amount of non-shared memory each of the child
>>> Apache processes are using (for example, I'm averaging 10 MB per process).
>>> Take the maximum amount of RAM you want Apache to use and divide it by this
>>> memory to get a rough number for MaxClients. You can monitor memory usage
>>> and adjust this as needed or through load testing.
>> 
>> 
>> I just set MaxClients 50 (on the basis of fat apache2 processes having
>> ~50MB discrepancy between RES and SHR). Let's see what happens.
>> 
>> 
>>> Of course, this is a solution to the usage of swap and not the actual issue
>>> you are having. I would continue to look at what is causing the surge in
>>> requests. Is it a DoS of some sort (either accidental or on purpose) or is
>>> some part of the server stalling which is causing requests to pile up and
>>> overflow? For example, if the database is having an issue (a bunch of long
>>> queries) then all Apache requests will start piling up until you hit swap
>>> or the database issue resolves itself.
>> 
>> 
>> I see that in busy times, the CPU usage goes way up and a chunk of it
>> is MySQL. I could be wrong, but this suggests to me complex requests
>> to MediaWiki (e.g. logged in editors right-clicking diffs on an
>> obscure page). I should probably profile MediaWiki, given we have a
>> pile of custom extensions.
>> 
>> 
>>> Along these lines I would suggest some sort of monitoring/logging service
>>> like Zabbix or Nagois (to name just two, there are many similar options to
>>> choose from). This helps you on two fronts: 1) Logging of Parameters and 2)
>> 
>> 
>> I live on our Munin graphs :-)
> 
> I know it's heretically commercial software, but I believe in and have used 
> New Relic at several client sites, and their free "lite" service level might 
> well help diagnose further...
> 
> 
> George William Herbert
> Sent from my iPhone
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