Re: [squid-users] How Squid behaves if we turn off Apache‏

store-stale might be useful too;
  http://www.squid-cache.org/Doc/config/refresh_pattern/

Cheers,

On 26/05/2011, at 2:35 PM, Amos Jeffries wrote:

> On Wed, 25 May 2011 10:16:46 -0700, melissa schellenberg wrote:
>> We're performing an upgrade on the CMS that is sitting behind Squid,
>> and we want Squid to serve up ALL pages from its cache during the
>> hour
>> or two of the upgrade, so that no requests are made to the CMS during
>> that time. Is there a "hero mode" setting that we can toggle in
>> Squid? Or should we be pre-loading all cached pages with long expiry
>> times beforehand?
>> I've been reading some rather old threads "offline mode" but that
>> seems to be applying only to forward proxying. Thanks in advance for
>> any help!
>
> There is a magic option. The very badly named "offline_mode" causes
> squid to grab things as greedily as possible for caching. Turn it ON for
> a while leading up to the outage, some days usually.
>
> Also, run a check of the Expires: headers being used by site content.
> That is an absolute limit on cache storage. Bumping up the short ones to
> after the outage is over will reduce unavailable objects for the
> duration.
>
> Check max_stale (if available in your Squid) is set much longer than
> the outage time. Several multiples of the outage period would probably
> be best, this has to cope with data stored at the start of the
> offline_mode turn-on as well as stuff requested just before outage.
>
> Remove "must-revalidate" and "proxy-revalidate" cache controls wherever
> possible for a while leading up to the outage. This trades problems with
> unavailable objects for problems with stale objects, so care is needed.
> In general if you can easily remove a must-revalidate safely you may
> benefit long-term by leaving it that way :)
>
> Also, maybe have a "sorry downtime" page to redirect posts to:
> acl POSTs method POST PUT
> deny_info http://example.com/sorry.html POSTs
> http_access deny POSTs
>
>
> You likely will miss some things. But those will help a lot.
>
>
> Alternatively, if this is super critical you could start the outage by
> taking a static mirror of the site then pointing Squid to use that
> temporarily. Sending this static copy with a fixed Expires: set to the
> end of the upgrade outage will make all new requests transition to the
> new site version at a easily determined time.
>
> Amos
>

--
Mark Nottingham       mnot_at_yahoo-inc.com