Re: [squid-users] Initial squid impressions (and questions)

vda wrote:
>
> Hi squid people,
>
> [I subscribed 43 seconds ago ;), please CC me just in case
> subscription went wrong]
>
> Just installed squid (squid-2.5.STABLE1-20021119).
> I'd like to configure it to be aggressively caching,
> so I'm suspicious to any events when it goes to the Net
> seemingly without need.
>
> Here: my browser has http://www.xfree86.org/isc.gif
> in it's cache, so it asks Squid:
> "If-Modified-Since: Tue, 08 Oct 2002 19:50:42 GMT; length=3768" ?
> Squid does not have it in the cache (I just recreated empty cache
> directories), so it goes to the www.xfree86.org, asks the same,
> receives "HTTP/1.1 304 Not Modified", reports that to the browser.
>
> The problem is, it will go to www.xfree86.org again and again
> whenever I visit the site as long as browser has that .gif internally
> cached. This looks suboptimal for me. "Clear all caches of all

 Does it ? Note that the hole process is of fetching objects
is browser driven.
If the browser has the object in it's cache, the only thing
it has to be sure off , is that it has the latest version.
So the browser must make sure that the object is fresh.
There is no other alternative to make then to make an if-modified-since
request to the cache.

UNLESS 'freshness' information is being returned from the remote
webserver.
Apparently this information is not available for this object, so
the browser and subsequent cache-chain are behaving correctly.

Checkout

 http://www.ircache.net/cgi-bin/cacheability.py

  You may want this tool usefull.

> browsers on each and every client machine whenever you recreate
> your squid cache" type recipe is wrong: I have far too many of them.
>
> Okay, now I'll purge browser cache. Go for the .gif again.
> First time, it gets cached (TCP_MISS in access.log).
> Next time? TCP_REFRESH_HIT! From the FAQ: "TCP_REFRESH_HIT:
> The requested object was cached but STALE. The IMS query for
> the object resulted in '304 not modified'".
>
> I had similar problems when squid's box had wildly wrong
> system date (~1992 ;), but now date is correct.
>
> What's even more puzzling, http://www.xfree86.org/xfree86.logo.gif
> does NOT exhibit this. I get TCP_IMS_HIT on second and subsequent
> accesses, which is normal. Why?! Anyone with cluebat?

 The only difference between the 2 cases I can see is that for
 the first object it was already in the browser cache.
 And for the second it is in the SQUID cache already,hence
 the different access states.

 But for neither objects the remote webserver is giving
 freshness information.
 
 M.

>
> I'm interested in any comments. Full access.log and squid.conf
> are attached if you want to know the details (tar.gz).
>
> Abridged access.log:
> ====================
> TCP_MISS/304 192 GET http://www.xfree86.org/isc.gif - DIRECT/204.152.184
> TCP_MISS/304 192 GET http://www.xfree86.org/isc.gif - DIRECT/204.152.184
> TCP_MISS/304 192 GET http://www.xfree86.org/isc.gif - DIRECT/204.152.184
> TCP_MISS/200 4065 GET http://www.xfree86.org/isc.gif - DIRECT/204.152.18
> TCP_REFRESH_HIT/304 191 GET http://www.xfree86.org/isc.gif - DIRECT/204.
> TCP_REFRESH_HIT/304 191 GET http://www.xfree86.org/isc.gif - DIRECT/204.
> TCP_REFRESH_HIT/304 191 GET http://www.xfree86.org/isc.gif - DIRECT/204.
> TCP_MISS/200 27349 GET http://www.xfree86.org/xfree86.logo.gif - DIRECT/
> TCP_IMS_HIT/304 214 GET http://www.xfree86.org/xfree86.logo.gif - NONE/-
> TCP_IMS_HIT/304 214 GET http://www.xfree86.org/xfree86.logo.gif - NONE/-
> TCP_IMS_HIT/304 214 GET http://www.xfree86.org/xfree86.logo.gif - NONE/-
>
> Startup squid messages:
> =======================
> 2002/01/02 13:59:56| Starting Squid Cache version 2.5.STABLE1-20021119 for i386-pc-linux-gnu...
> 2002/01/02 13:59:56| Process ID 9179
> 2002/01/02 13:59:56| With 1024 file descriptors available
> 2002/01/02 13:59:56| Performing DNS Tests...
> 2002/01/02 13:59:56| Successful DNS name lookup tests...
> 2002/01/02 13:59:56| DNS Socket created at 172.16.42.127, port 1027, FD 7
> 2002/01/02 13:59:56| Adding nameserver 172.16.42.127 from /etc/resolv.conf
> 2002/01/02 13:59:56| Unlinkd pipe opened on FD 12
> 2002/01/02 13:59:56| Swap maxSize 102400 KB, estimated 7876 objects
> 2002/01/02 13:59:56| Target number of buckets: 393
> 2002/01/02 13:59:56| Using 8192 Store buckets
> 2002/01/02 13:59:56| Max Mem size: 8192 KB
> 2002/01/02 13:59:56| Max Swap size: 102400 KB
> 2002/01/02 13:59:56| Rebuilding storage in /var/app/squid-2.5.STABLE1-20021119/cache (CLEAN)
> 2002/01/02 13:59:56| Using Least Load store dir selection
> 2002/01/02 13:59:56| Set Current Directory to /var/app/squid-2.5.STABLE1-20021119/cache
> 2002/01/02 13:59:56| Loaded Icons.
> 2002/01/02 13:59:56| Accepting HTTP connections at 172.16.42.127, port 3128, FD 13.
> 2002/01/02 13:59:56| WCCP Disabled.
> 2002/01/02 13:59:56| Ready to serve requests.
> 2002/01/02 13:59:59| Done scanning /var/app/squid-2.5.STABLE1-20021119/cache swaplog (0 entries)
> 2002/01/02 13:59:59| Finished rebuilding storage from disk.
> 2002/01/02 13:59:59| 0 Entries scanned
> 2002/01/02 13:59:59| 0 Invalid entries.
> 2002/01/02 13:59:59| 0 With invalid flags.
> 2002/01/02 13:59:59| 0 Objects loaded.
> 2002/01/02 13:59:59| 0 Objects expired.
> 2002/01/02 13:59:59| 0 Objects cancelled.
> 2002/01/02 13:59:59| 0 Duplicate URLs purged.
> 2002/01/02 13:59:59| 0 Swapfile clashes avoided.
> 2002/01/02 13:59:59| Took 3.1 seconds ( 0.0 objects/sec).
> 2002/01/02 13:59:59| Beginning Validation Procedure
> 2002/01/02 13:59:59| Completed Validation Procedure
> 2002/01/02 13:59:59| Validated 0 Entries
> 2002/01/02 13:59:59| store_swap_size = 0k
> 2002/01/02 14:00:00| storeLateRelease: released 0 objects
> --
> vda
>
> ------------------------------------------------------------------------
> Name: access_conf.tar.gz
> access_conf.tar.gz Type: Unix Tape Archive (application/x-tar)
> Encoding: base64

-- 
 'Time is a consequence of Matter thus
 General Relativity is a direct consequence of QM
 (M.E. Mar 2002)