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

Thanks very much for the detailed explanation. This is exactly what we're looking for! We have enough time in advance to do some "greedy pre-loading"!

> To: squid-users_at_squid-cache.org
> Date: Thu, 26 May 2011 16:35:50 +1200
> From: squid3_at_treenet.co.nz
> Subject: Re: [squid-users] How Squid behaves if we turn off Apache‏
>
> 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
>
                                               
Received on Thu May 26 2011 - 18:13:31 MDT