Re: [squid-users] Re: Stale-if-error , does it work?

Dingwell, Robert A. wrote:
>
>
> On 3/26/09 11:01 AM, "Dingwell, Robert A. (BOBD)" <bobd_at_mitre.org> wrote:
>
>> I¹ve been trying to get a caching architecture setup so that if a server I
>> am caching content for goes down or is more likely just unavailable to do
>> network issues I can have the cache serve up the stale content. In the
>> production environment that this will be used I will not have the ability to
>> have all of the services involved set cache control headers on their data. We
>> are operating on a wan with people all over the globe so it would be really
>> difficult to get everyone to do that. What I can do though is to make sure
>> that everything goes through apache acting as a reverse proxy which then sets
>> the Cache-Control header, which I have done and verified that it does indeed
>> do what I want it to.
>>
>> So now I fire up squid and apache and attempt to access a server I have
>> control over and I get back the data I expect to get back. Look in the squid
>> log file see the header in the log ³Cache-Control: stale-if-error=300² so I
>> know it¹s being sent. Now I shutdown the server I just accessed and attempt
>> to access the same url. I expect to get back the same data that I just got
>> back but instead I get back the error page saying the service is unavailable.
>> Shouldn¹t squid be serving up the stale content? Or am I missing a step. The
>> other odd thing is once I start the server back up it takes a couple of
>> minutes to get back the page from server as squid seams to be caching the
>> error page.
>>
>> I know that stale-if-error is only going to work for 500-504 errors but
>> looking through the squid logs again I see that I am getting an error code
>> back when I try to access the page when it¹s down ³HTTP/1.1 503 Service
>> Temporarily Unavailable².
>>
>> One last thing this article , http://www.mnot.net/blog/2007/12/12/stale ,
>> makes it sound like squid has a configuration parameter that is used to enable
>> stale-if-error even when the server does not send the control header. Does
>> anyone know if this exists or what the magic incantation is to get it working?
>>
>> Anybody have any ideas as to what I may be doing wrong, or an alternative
>> approach to accomplishing what I am trying to get working? I already tried
>> using offline mode which did not work and I think isn¹t really what I would
>> want to do anyway as I need squid to attempt to access the server and serve up
>> the stale data only when the server is down.
>>
>> Any help is appreciated ,
>>
>> Thanks
>> Rob
>

Depends.
Squid-2.7 supports it, the others do not yet though there is a patch for
Squid-3.1 in bugzilla awaiting someone to test it properly.

Amos

-- 
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