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I have multiple virtual hosts set up. On one of them, let's say three out of ten page loads are basically instant. The other seven always take (pretty much) exactly 5 seconds of server lag (as opposed to data transfer).

It doesn't matter which page is loading, or whether or not it's a Drupal page.

There are a lot of requests each second, and I'm wondering if Apache is putting requests on standby until it's finished with the current queue, or something along those lines?


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Isn't something that is randomly predictable an oxymoron? –  Naftuli Tzvi Kay Aug 7 '11 at 22:02
I guess so, what I meant was that it was random when it happened but you knew it would happen soon ;-) –  Fela Maslen Aug 7 '11 at 22:37
Perhaps "recurring" or "recurrent" would be a better word. –  Naftuli Tzvi Kay Aug 7 '11 at 23:01
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2 Answers

It could be server queueing (server-status should tell you that), but from the precision and consistency of the delay, I'd be inclined to think it's probably rDNS lookups timing out -- which is why everyone turns it off (with HostnameLookups Off).

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How would I turn off rDNS lookups then? :P –  Fela Maslen Aug 7 '11 at 22:38
Hmm...hang on it looks like it is definitely a problem induced by high traffic from multiple sources. So I bet it must be server queuing. Maybe I could try raising the queue length, only thing is this is a single core 2.2GHz CPU... –  Fela Maslen Aug 7 '11 at 23:18
If your server is overloaded, reduce the load (optimize, load balance) or get a bigger server. –  womble Aug 7 '11 at 23:25
Sadly that's not an option so for now, I'm just going to live with the lag. Thanks for the help though :) –  Fela Maslen Aug 8 '11 at 0:56
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I'd have a look at mod_status to help debug the issue. It gives a good incite into what apache is up to, and can often indicate where to start debugging a problem (script/apache config/etc).

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I heard about that but could never get it going. –  Fela Maslen Aug 12 '11 at 0:16
@Fela - it should be pretty simple, once you have the module loaded just drop this config in: pastebin.com/vz5H5QyW –  Coops Aug 12 '11 at 5:14
Heh, I made a new directory and put that in the .htaccess and it finally works :P Thanks :) –  Fela Maslen Aug 14 '11 at 15:15
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