Re: [squid-users] Offline mode with a parent cache doesn't work

londoner1_at_hushmail.com wrote:
> On Thu, 25 Jun 2009 05:44:24 -0700 Amos Jeffries
> <squid3_at_treenet.co.nz> wrote:
>> londoner1_at_hushmail.com wrote:
>>> Hi,
>>>
>>> I am trying to setup a local squid cache on my laptop so that I
>> can
>>> browse intranet pages when I am on a plane and don't have
>> network
>>> connection.
>>>
>>> I am therefore using the squid offline_toggle option via the
>>> 'squid3client mgr:offline_toggle' command.
>>>
>>> However, I am finding that pages are not being cached when I
>> have
>>> my Office proxy set as a parent to my local one.
>>>
>>> I am running ubuntu hardy with squid 3 STABLE.1 ubuntu package
>> on
>>> my local machine, with a parent proxy set using the following
>> lines
>>> in my squid.conf:
>>>
>>> cache_peer proxy.nectech.co.uk parent 8080 0 no-query
>>> prefer_direct off
>>>
>>> PS: The above two lines came from Squid wiki here:
>>> http://wiki.squid-cache.org/SquidFaq/ConfiguringSquid#head-
>>> c050a0a0382c01fbfb9da7e9c18d58bafd4eb027
>>>
>>> My approach to test this is as follows:
>>>
>>> 1 Set firefox to my localhost:3128 proxy
>>> 2 Start squid in online mode and browse to a website.
>>> 3 Close firefox
>>> 4 Set local squid into offline mode using 'squid3client
>>> mgr:offline_toggle'
>>> 5 Pull out the Network cable (to simulate being on a plane)
>>> 6 Reopen firefox and browse to same site as in step 2.
>>>
>>> After step six, the page does not load and eventually times out.
>>>
>>> If i take out the parent cache lines, the offline mode will
>> work.
>>> Please can anyone help?
>> 'offline_mode' means that Squid no longer attempts page validation
>> and
>> fetching of new pages. It does not means supplying content known
>> to be
>> past expiry.
>
> Hi Amos,
>
> Ok, please forgive me if I dont understand you correctly: you are
> saying that the local squid cache is NOT returning me the page that
> i previously went to a few minutes ago because it thinks it has
> expired?

Yes. From the info provided I believe that is what is happening.

>
> why would it be expired that quickly? and yet not be expired if my
> local squid cache does not use the parent cache?

HTTP contains things called If-Modified-Since requests. When squid
thinks something is expired it either uses them or a new request to
check for new content. Sometimes an IMS request sens back "no hasn't
chaged" so Squid updates its information and sends you the object again.

It's probably that the HTML part of the page has a short expiry time but
does not actually change (ie a dynamically created page).

Even if all the images etc on the page are available for months, without
an HTML part to say how they are displayed the page wont show up.

>
> Also, a poster on the following blog mentioned that squid offline
> mode ignores expiry data for cached items when in offline mode. Is
> this not the case in latest squid 3 versions?
>
> http://people.w3.org/~dom/archives/2006/09/offline-web-cache-with-
> squid/
>
> ps I appreciate your help on the subject.

Mark who replied there and others have made a lot of improvements to the
expiry and IMS sections of the latter Squid 2.6 releases and 2.7.

The Squid-3 code in the same areas is a lot older with not all of their
changes ported over. So I believe it would behave differently. Though
I'm not fully clued up on the finer grains of whats going on there.

Amos

-- 
Please be using
   Current Stable Squid 2.7.STABLE6 or 3.0.STABLE16
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