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 Post subject: Re: Server hiccups
PostPosted: Sun Apr 27, 2008 2:12 pm 
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Forum Regular
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Joined: Sat Oct 08, 2005 8:18 pm
Posts: 705
Location: Windermere, FL
Are you running any control panel, like cPanel? It could be a service like ClamAV or the common pkgacct process that is known to hang for long periods of time and cause higher server loads.

Is there a spiked server load when the site slows down?

Have you considered that it may be a problem with your host? In other words, you may be on a bad vlan (do you share an uplink?), or they may be rebooting their switches due to constant ddos attacks, etc.. and some of these switches have bad table routing. The IP that devnet is on... is it shared with any other websites? If so, it could be a DNS issue... your DNS could be incorrectly cached for various points in various DNS servers. This likely isn't the issue if you use custom nameservers and host your own DNS zone files... but if your host manages DNS for you... they could be mucking it up using zone files that are automatically regenerated every X minutes on their DNS server.


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 Post subject: Re: Server hiccups
PostPosted: Sun Apr 27, 2008 9:25 pm 
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Breakbeat Nuttzer
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Joined: Wed Mar 24, 2004 8:57 am
Posts: 13098
Location: Melbourne, Australia
We found out the cause. A crap load of apache processes were exhausting our memory and also our swap. This causes all kinds of issues. The reason for such a high number of apache processes is still unknown, and perhaps a tad suspicious, but what we've done is:

a) Increase the amount of swap space
b) Reduce the number of allowed apache processes significantly (this means you'll get the occassional "hang" while the page is loading because your request is queued; but that's only when we're crazy busy)
c) Reduced PHP's memory limit. God knows why, but phpBB3 cannot run under 8MB of memory so we have to set it higher. Something to look into
d) Set up a squid reverse proxy. Instead of ~20 requests to load the "Post a reply" page for example, there will now only be one request hitting apache. The rest will come from Squid's cache.

All in all we seem to running a lot more smoothly. We get the occasional "hang" for 10-15 seconds, but it subsides gracefully and it's nothing out of the ordinary. We are still optimizing however.


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 Post subject: Re: Server hiccups
PostPosted: Mon May 19, 2008 12:08 pm 
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Site Administrator
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Joined: Tue Sep 09, 2003 6:04 pm
Posts: 14293
Location: Fremont, CA, USA
The hang issue is actually a subset of a larger issue that we are looking for an appropriate window of time to correct. Right now, when the site hangs, there is a good chance that it will at some point pop back as we are now using a proxy to serve up pages. However there are times when things still go alittle wobbly and at times like this we usually have an admin around to get things back on track.


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 Post subject: Re: Server hiccups
PostPosted: Thu Feb 12, 2009 2:40 pm 
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DevNet Master

Joined: Wed Feb 11, 2004 4:23 pm
Posts: 4872
Location: Palm beach, Florida
I'm unable to send PMs?


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 Post subject: Re: Server hiccups
PostPosted: Thu Feb 12, 2009 2:42 pm 
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Site Admin
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Joined: Tue Dec 23, 2003 3:10 am
Posts: 11470
Location: Toronto
josh wrote:
I'm unable to send PMs?


What happens?


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 Post subject: Re: Server hiccups
PostPosted: Thu Feb 12, 2009 3:31 pm 
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DevNet Master

Joined: Wed Feb 11, 2004 4:23 pm
Posts: 4872
Location: Palm beach, Florida
After I hit send it goes to a blank page. I'll test real quick again on your name
Edit: worked. Don't know? Im not cryin wolf! I tried it several times before.


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