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On one of my hosting I am sometimes getting error that generates 503 response.

[notice] [client mod_overload: Overloaded, 1 minute load average, current load: 101, max load allowed: 90

I have tried to google it but there is not much information about this error nor about mod_overload itself.

My guess is that this mod sends 503 code if the is more than allowed number of request at one time.

Could someone confirm if I am right or not and if not what does it do.

PS: I have send email to hosting company for explanation but would like to get answer from independent sources as well.

Edit:

Apache module which is checking load average and when it is higher then defined stops current request(has ability to stop other request too). Since 0.2 settings can be set per directory/virtualhost/location.

For me this one paragraph doesn't give much of explanation about how this mod works or to be more precise how it calculates load average. Which variables does it takes into account is it only CPU and memory usage, maybe number of parallel request? How big influence may have a website's code?

The website I have this problem with was not developed by me but I just got to modify it and find source of this error. It has some poor quality code, there was lots of PHP warnings at each request that were always written to log files. Could it be a reason of increased load?

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closed as off-topic by Falcon Momot, Ward, dawud, mdpc, Tim Brigham Aug 16 '13 at 20:34

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This is something your shared hosting provider, who are the system administrators, has configured. It is entirely theirs to explain. –  Falcon Momot Aug 16 '13 at 2:29
    
@FalconMomot they are not mod_overload developers so I guess someone here can explain a bit more about it. –  Gustek Aug 16 '13 at 9:43
    
@Gustek If you're not the sysadmin you need to ask your sysadmin, not us. (Or you could, yanno, Google -- the first result for mod_overload is sourceforge.net/projects/modoverload which explains what mod_overload does.) -- I'm really not trying to be mean, but a Google search is kind of the bare minimum standard of effort before posting questions here. –  voretaq7 Aug 16 '13 at 20:19

1 Answer 1

up vote 2 down vote accepted

Sounds like you're on a shared web-hosting server and it's unable to cope with the incoming http requests (not just for your site(s) but for everyones). One way to ensure this doesn't happen is to have a degree of dedicated resources and control over their allocation by using a VPS or Dedicated Server to host your site. Otherwise, there's not much you can do about these kinds of things; besides find a web host that won't overload their servers - and even then you're vulnerable to traffic spikes from sites that are sharing your same server.

If you don't understand what load average represents on a server, I suggest looking into that more to understand what resources are being contented for on this server and how it adversely affects your personal site performance. Apache is dropping http requests because the CPU is busy doing other things at the moment - most likely serving other http requests. From my reading of http://sourceforge.net/projects/modoverload/ that seems to be the exact purpose of this apache module, to basically provide a tunable element for virtual hosts and sites to ensure that no one of them or cluster of them starve off the rest of the sites on the server for essential resources.

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