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RE: How not to make an error page (was: OT: www.Amazon.com down?)

From: "Andy Litzinger" <Andy.Litzinger () theplatform com>
Date: Fri, 6 Jun 2008 11:49:42 -0700
I've no idea what Amazon uses for Load Balancers, but I'm pretty sure
that error message is the default error message served up by a Netscaler
LB if no web services are available in the pool...

-andy


-----Original Message-----
From: Kevin Day [mailto:toasty () dragondata com]
Sent: Friday, June 06, 2008 11:40 AM
To: Lasher, Donn
Cc: nanog () nanog org
Subject: How not to make an error page (was: OT: www.Amazon.com down?)


On Jun 6, 2008, at 1:24 PM, Lasher, Donn wrote:


Checked, and doublechecked, not just me

www.amazon.com returns:

Http/1.1 Service Unavailable

Anyone have a URL for a network/etc status page, or info on the
outage?
Been that way for a while this morning.

-donn




Even worse, the page they're displaying is actually a HTTP 200
response code(OK/no error), with no "Don't cache this" header - which
means their error page is considered cacheable by some browsers/
proxies. So, you may find users who tried to visit Amazon while they
were down are still seeing it down long after they fix it.

Lesson to high profile websites: add these to your error pages so you
don't have people complaining you're still down long after you're
fixed.

* Don't return a 200 response code. Use 500 or 503. Nothing from 2xx
or 4xx.
* Add a "Cache-control: no-cache, must-revalidate, max-age=0" header,
as well as an "Expires: 0" header for good measure.
* If your server is really borked and you can't add headers at all,
add '<META HTTP-EQUIV="Pragma" CONTENT="no-cache">' to the <head>
section. That's not as good, but helps at least on the browser end.
* If possible, add a timestamp to the page somewhere (even if it's in
an HTML comment) so you can troubleshoot with users still seeing the
error.

-- Kevin
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