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San Francisco (Time to First Byte) - Printable Version

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San Francisco (Time to First Byte) - TDF - 10-04-2011 11:41 PM

Hi,

I've ran tests from all available locations and the site loads almost perfectly worldwide.

However the test from San Francisco is really bad. The time to first byte is terribly long.

http://www.webpagetest.org/result/111004_JT_1SN78/

For comparison here are two tests from Dulles, VA and Bangalore, India

http://www.webpagetest.org/result/111004_KG_1SNAE/

http://www.webpagetest.org/result/111004_95_1SNCD/

What can possibly be the cause of this? Any thoughts?


RE: San Francisco (Time to First Byte) - pmeenan - 10-05-2011 12:27 AM

I ran a sanity test just to make sure there wasn't a problem with the agent: http://www.webpagetest.org/result/111004_G7_ff7ccb5350ffc3b90381af52bfe53457/

The only guesses I have are:
1 - some form of server DOS protection that is holding down the connections from the SF agent
2 - some really screwy routing between the SF agent and your server (though I'd expect that to show up in the socket connect time)
3 - a problem with the test agent that only manifests itself on your site

I grabbed a packet capture to get a better idea of what is going on: http://www.webpagetest.org/result/111004_6A_c9edcb6f78e4b9f598a2c3f570bb4db8/

It looks like the server ACK'd the actual HTTP request and then 20 seconds later the response started coming so from a network perspective it looks fine (but slow).

If you don't already have it turned on, you can add the server response time to your access log and then tail the access log with a grep filter for PTST which will only show requests from WebPagetest. That way you can at least tell if it is somewhere in the application or in front of it.

Thanks,

-Pat


RE: San Francisco (Time to First Byte) - TDF - 10-05-2011 01:50 AM

Thanks @pat,

I'll look into it. Meanwhile here are the results (screenshots) provided by Uptrends (full html web page test) and Pingdom (Check type: HTTP).

Uptrends
[attachment=141]

Pingdom
[attachment=140]

From the above I think that the problem it's not on the server (website) end at all.


RE: San Francisco (Time to First Byte) - TDF - 10-05-2011 04:19 AM

It's confirmed. It's not the server, nor the website. Double checked with the hosting company, they've also tested the site from SF and there is no problem.

Obviously it's a problem with the SF test agent that only manifests itself on the site.


RE: San Francisco (Time to First Byte) - pmeenan - 10-05-2011 05:55 AM

ok, thanks. I'll try several other sites to see if I can track it down. Could be an issue going out from the fastsoft node.


RE: San Francisco (Time to First Byte) - pmeenan - 10-13-2011 01:34 AM

The San Jose agent is now online with IE 8, 9, Chrome, Firefox 3.6 and Firefox 7. Sorry about the issues with the San Francisco agent (which I also took offline).

Thanks,

-Pat