Re: [squid-users] Squid Accellerator with ethernal cache for fault tollerance

On 19/04/2013 8:00 p.m., Daniele Segato wrote:
> Hi,
>
> my need is to have Squid caching request to my server like this:
> * do NOT bother the server more then once per minute to check if an
> update is available
> * if the server return a 500, go into timeout or something like this
> during an update keep sending the cached resource to the user
>
> Ideally I would like to be able to turn off the server for maintenance
> while the Squid frontend keep returning request.
>
> I've been trying to achieve this for a while now without success.
>
> Is this possible?

Yes. These are both HTTP features.

> Can you address me in the right direction?
>

The bit you are missing is the stale-* cache controls. See
http://www.mnot.net/blog/2007/12/12/stale

Squid supports stale-if-error since 3.2, but not yet
stale-while-revalidate. There is a bit more internal plumbing to be
created before that will work properly.

> Thanks.
>
> This is my configuration file (included in the main squid.conf):
> Which currently cache updating every minute but start givin error
> after that minute if the server is took down.
>
>
> # http://wiki.squid-cache.org/SquidFaq/ReverseProxy
> # http://www.visolve.com/squid/whitepapers/reverseproxy.php
> #
> http://www.howtoforge.com/how-to-set-up-a-caching-reverse-proxy-with-squid-2.6-on-debian-etch
> #
> http://www.linuxhomenetworking.com/wiki/index.php/Quick_HOWTO_:_Ch32_:_Controlling_Web_Access_with_Squid
>
> http_port localhost:280 accel ignore-cc defaultsite=localhost

Ah the good old localhost. Nice to know you have installed a web server
there for all clients to access your website http://localhost/ with ...

> cache_peer localhost parent 8080 0 no-query originserver no-digest
> default name=myAccel
>
> refresh_all_ims off
>
> # IP address of web server
> #httpd_accel_host 127.0.0.1
> # Port of web server
> #httpd_accel_port 8080
> # Forward uncached requests to single host
> #httpd_accel_single_host on
> #httpd_accel_with_proxy on
> #httpd_accel_uses_host_header off

The above are all config options from squid-2.5 an older. No time like
now to drop them completely.

> acl Safe_ports port 280
> http_access deny !Safe_ports
>
> acl our_sites dstdomain 127.0.0.1 localhost mobc3.local
> http_access allow our_sites
> cache_peer_access myAccel allow our_sites
> cache_peer_access myAccel deny all
<snip comments>
> # cache services
> refresh_pattern /alfresco/service/catalog 0 20% 4320
> refresh_pattern /alfresco/service/stream 0 20% 4320
> refresh_pattern /alfresco/service/news 0 20% 4320
> # do not cache everything else
> refresh_pattern . 0 20% 0

All of the values on refresh_pattern line has meaning and may be applied
independent of the other values. That 20% does something other than "do
not cache", so you probably want that to be "0%".

Amos
Received on Fri Apr 19 2013 - 10:16:32 MDT