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Date: Thu, 09 Dec 2010 10:22:24 -0800
From: "Craig A. James" <cjames@emolecules.com>
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Subject: Re: [users@httpd] Some VirtualHosts extremely slow, others very fast

On 12/8/10 10:15 PM, Igor Cicimov wrote:
> Check the dns resolution for the xyz host.

There is no problem with DNS.  All of the subdomains use the wildcard *.ourdomain.com, which resolves to both www and xzy.  The problem isn't with DNS.  Each TCP/IP conversation starts instantly.  But with xyz.ourdomain.com, every HTTP GET request ends up with a five-second delay in the middle of the TCP/IP stream.  It's very consistent.

Thanks,
Craig

>
> Sent from my phone
>
>> On Dec 9, 2010 1:24 PM, "Craig A. James" <cjames@emolecules.com <mailto:cjames@emolecules.com>> wrote:
>>
>> We operate one public web site and about 20 private web sites.  They're all the same server, running the same Apache server instance (2.2.14-5ubuntu8.3).
>>
>> Most customers get excellent performance, but two customers get terrible response times, but only on *some* of the VirtualHosts.  They get excellent responses from our public site, but the very same page served from a private site can take over a minute to load.
>>
>> The VirtualHosts are configured identically except for the "Allow from" and "ServerName" directives.  As far as I can tell, everything else is identical (except the specific database it uses, but for these tests we're only loading static HTML pages).
>>
>> It appears that "www.ourdomain.com <http://www.ourdomain.com>" VirtualHosts always work, but "xyz.ourdomain.com <http://xyz.ourdomain.com>" VirtualHosts give problems.
>>
>> Examining TCP/IP traffic using WireShark, it looks like the slow virtual hosts are dropping ACK packets.  Each TCP/IP conversation starts out fast, but then there's a 5-second gap in the middle of every HTTP response.  Yet if the very same user accesses a different VirtualHost, there is no problem at all.
>>
>> We've been trying to figure this out for weeks with no luck.  Any ideas would be greatly appreciated.
>>
>> Craig
>>
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