[squid-users] TCP_REFRESH_MISS and zero response code strangeness

Hello Squidheads!

We've got Squid running in http accel mode, and for the most part it's
working great. We add expires headers to the content generated by our
source server, and for the most part everything works really well. In the
normal case we see lots of TCP_REFRESH_HITs and everything seems happy.

However, under certain circumstances we see lots of TCP_REFRESH_MISS:DIRECT
and TCP_REFRESH_MISS:NONE codes in our logs, in both cases accompanied by 0
(vs 200, 404, etc) HTTP response codes in the Squid access logs.

When we start seeing these it seems to be accompanied by a big slowdown in
our system. There aren't any obvious error conditions showing up in our log
files however which point to a problem.

So, some questions:

1. Is a TCP_REFRESH_MISS:NONE with a 0 response code an expected, and
legal, condition for Squid? I'd think this would indicate a case in which
Squid thinks the image is stale, but it's in memory so it just returns it
without contacting a source server.

2. Is a TCP_REFRESH_MISS:DIRECT with a 0 response code an expected/legal
condition for Squid? I'm quite as sure how this would be generated--the
'DIRECT' indicates Squid contacted the source server, but
the 0 response code seems like it would indicates that it didn't get
anything back that it could understand. We don't believe that our source
server would do this to Squid.

3. What, in general, causes a 0 response code to show up in the Squid logs?
Does this always indicate an error condition, or are there normal conditions
for which this would
occur?

4. Are there scenarios associated with the above codes that could cause a
quite significant performance degradation, which is what we're seeing?

Thanks in advance for any help.

Squidless in Seattle

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Received on Tue Mar 26 2002 - 16:50:35 MST