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

Kevin Day toasty at dragondata.com
Fri Jun 6 13:40:18 CDT 2008


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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