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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