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From Tom Evans <tevans...@googlemail.com>
Subject Re: [users@httpd] Cache issues
Date Mon, 28 Sep 2009 14:43:27 GMT
On Mon, 2009-09-28 at 06:25 -0400, Phil Pinkerton wrote:
> 
> Jonathan Zuckerman wrote:
> > On Fri, Sep 25, 2009 at 10:54 AM, Phil Pinkerton <pcpinkerton@gmail.com> wrote:
> >   
> >> On Fri, Sep 25, 2009 at 12:45 PM, Jonathan Zuckerman <j.zuckerman@gmail.com>
> >> wrote:
> >>     
> >>> On Fri, Sep 25, 2009 at 6:15 AM, Phil Pinkerton <pcpinkerton@gmail.com>
> >>> wrote:
> >>>       
> >>>> Anyone experience performance issues with regards to Apache cache ?
> >>>>
> >>>> Â From time to time we are experience access issues ( users accessing
> >>>> Subversion ) that seem to be due to an over loaded Apache cache. We
> >>>> suspect
> >>>> the cache because when we refresh (stop,start) the Apache server the
> >>>> problems goes away for a time. This happens so regularly we have set
> >>>> crontab
> >>>> to refresh every morning during our maintenance period. And this has
> >>>> reduced
> >>>> the number of problems.
> >>>>
> >>>> This is Apache 2.2.11 running on a Solaris Sparc server. Providing HTTPD
> >>>> services for or Subversion users,
> >>>>
> >>>> Any thoughts on managing Apache Cache ?
> >>>>
> >>>> --
> >>>> " The fundamental principle here is that the justification for a
> >>>> physical
> >>>> concept lies exclusively in its clear and unambiguous relation to the
> >>>> facts
> >>>> that it can be experienced" Â  AE
> >>>>
> >>>> Please Feed and Educate the Children... it's the least any of us can
do.
> >>>>
> >>>>
> >>>>         
> >>> Is there anything at all in the error log to suggest it's the cache? I
> >>> think that bouncing the web server affects a lot of other stuff
> >>> besides the cache..
> >>>
> >>>       
> >> Nothing in the logs tells us anything about why we get the "Other" error
> >> messages, but if it's not a cache problem (possibly related to LDAP), why
> >> would a recycle fix it?
> >>     
> >>> ---------------------------------------------------------------------
> >>> The official User-To-User support forum of the Apache HTTP Server Project.
> >>> See <URL:http://httpd.apache.org/userslist.html> for more info.
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> >>>
> >>>       
> >>
> >> --
> >> " The fundamental principle here is that the justification for a physical
> >> concept lies exclusively in its clear and unambiguous relation to the facts
> >> that it can be experienced" Â  AE
> >>
> >> Please Feed and Educate the Children... it's the least any of us can do.
> >>
> >>
> >>     
> >
> > When you restart the webserver every thread completes and stops
> > handling requests, every process ends, _everything_ about the
> > webserver stops and then starts again, this potentially affects more
> > than just the files used by mod_cache.
> > Have you looked at the diskspace used by mod_cache to see if there are
> > any patterns to it (size, usage, whatever) when the webserver stops
> > responding?  How about monitoring the health of the box to see if
> > anything else could be the issue (CPU pegged, RAM, disk..)?  Anything
> > at all in apache error logs.
> > I'm sorry that I don't have more suggestions; mod_cache might indeed
> > be the problem but from a troubleshooting standpoint it seems to me
> > that you're narrowing down the possible causes just a bit too
> > recklessly.
> >
> >   
> Not sure you need to be so abusive. When this issue arises  100's of 
> developers  cannot access Subversion, several automated scripts fail to 
> checkout from Subversion and it could literally halt production. We 
> quickly implemented this "band-aid" to keep production running and since 
> the refresh takes only about 3 seconds and works to clear the issue. I 
> would think letting production crash while taking detail RCA would be 
> much worse than reckless. We don't have the Apache expertise and we did 
> very well to at least find a short term solution. I asked this group for 
> help not criticism.
> 
> The unnecessary "reckless" comment aside your questions are valid and 
> maybe somewhat useful.
> 
> Thanks for the assistance.
> 
> Phil

How frequently does it occur if the cache is disabled?

Cheers

Tom


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