[squid-users] How to disable TCP_NEGATIVE_HIT?

Hi Squid Users,

I use squid to accelerate my website, for example www.example.com. In the
access.log, I found such

222.xx.yy.zz - - [22/Jul/2008:15:02:26 +0800] "GET http://www.example.com/
HTTP/1.1" 503 858 "-" "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2;
.NET CLR 1.1.4322)" TCP_NEGATIVE_HIT:NONE

Though I am sure that the backend web server is up and can provide service,
still the browser got 503 Service Unavailable error display.

I check the book 'Squid: The definitive guide', and found

TCP_NEGATIVE_HIT
        When a request to an origin server results in an HTTP error, Squid
may cache the response anyway. Repeated requests for these resources, within
a short amount of time, result in negative hits. The negative_ttl directive
controls the amount of time these errors may be cached. Also note that
errors are cached only in memory and never written to disk. The following
HTTP status codes may be negatively cached, subject to additional
constraints: 204, 305, 400, 403, 404, 405, 414, 500, 501, 502, 503, 504.

In Squid 2.6 configuration manual, it says, we can use negative_ttl to
control Time-to-Live (TTL) for failed requests.

My question is ,can we use
negative_ttl 0
to disable caching of failed requests, so the following visitors will not
get the TCP_NEGATIVE_HIT responses?

Best regards,
Xu Feng
Shanghai,China
Received on Wed Jul 23 2008 - 00:49:39 MDT