Re: [squid-users] squid cache TCP_REFRESH_MODIFIED

On 18/02/2012 12:26 a.m., parashuram wrote:
> Hi all,
> I am using squid to cache dynamic responses from my particular server
>
> everything working fine,
> When I make first request access.log has
> 1329473470.110 0 192.168.0.40 TCP_MISS/200 856 GET
> http://[ipv6address]:8080/.well-known/core - DIRECT/::1 text/html
>
> Next request it logs following
> 1329473479.050 0 192.168.0.40 TCP_REFRESH_MODIFIED/200 856 GET
> http://[ipv6address]:8080/.well-known/core - DIRECT/::1 text/html
>
> request is in cache but due to resources being changed response is
> from origin server( I've ignored must revalidated in refresh pattern).
> I wanted request should be served from cache even if its modified and
> log TCP_HIT or TCP_MEM_HIT in access.log.
> any idea what might be going wrong??? suggestion how to tell squid not
> send revalidiate signal to origin server to cross check for resource
> modification???
>
> server header response is as follows
>
> (Status-Line) HTTP/1.0 200 OK
> Date Fri, 17 Feb 2012 10:11:19 GMT
> Content-Type text/html
> Last-Modified Wed, 15 Feb 2012 07:48:34 GMT
> Accept-Ranges bytes
> Content-Lenght 8334
> Cache-Control max-age=86400,public

Notice how "must-revalidate" is not present. Your override turing it off
does nothing.

What is happening here is that max-age is specifying that the object is
stale when older than 1 day, and needs revalidatating. (Date minus
Last-Modified) is stating that it is currently 2 days old.

Squid is only performing a REFRESH (if-modified-since) check, this is
very efficient if the server supports them. Your service should be
checking the last-modified and returning 304 status response if it is
older. It can in that response update the max-age and Expires values to
push the expiry time forward if it wants to.

Amos
Received on Sat Feb 18 2012 - 04:32:11 MST