Re: Redundancy

From: David J N Begley <>
Date: Fri, 7 Nov 1997 10:52:23 +1100 (EST)

On Thu, 6 Nov 1997, WWW server manager wrote:

> * when asked to load a new configuration, Squid rejects connections while
> it writes a new cache/log file containing details of the current cached
> objects. On our server, that takes a 2-5 minutes.

Ouch! Is this something that can be fixed in software without risking the
integrity of the data, or is it a problem at which "bigger iron" should be
thrown? How different is this process from what happens when Squid first
starts up (it's still reading the log file, yet it responds to requests

At midnight our logs are rotated - at this point, Squid does a
"storeWriteCleanLog" .. upon its conclusion it reports:

97/11/07 00:00:52| Finished. Wrote 968123 lines.
97/11/07 00:00:52| Took 52 seconds (18617.8 lines/sec).

During that 52 seconds, users trying to desparately "click 'n' shoot" may
have a couple of false starts, but for the majority of users the delay is
completely unnoticed (or by the time they hit "reload", everything is
running again). Total complaints after >12 months of doing this - zero.

> while Squid seems to continue accepting connections and to maintain
> existing ones, those connections are "on hold" until it's finished
> writing out cache/log, which again may take 2-5 minutes on our server.

As above - can this be solved (properly) in software, or should more
horsepower be thrown at the problem?

> indicated in the original query, liable to result in users bypassing the
> cache and never bothering to use it again.

If it matters not to the site if the users go direct or via the proxy,
then who cares? If it *does* matter, then there are alternatives:

- force users to use the proxy;
- if users are charged for traffic volume, provide discounts for use of
  the proxy (ie., it becomes cheaper for users to wait for the proxy than
  to impatiently go direct);
- provide properly redundant proxying systems (a single front-end to a
  single back-end proxy isn't "redundancy"); or,
- throw enough grunt at the one proxy you have so that it *does* stay up
  without imposing unbearable delays on proxy usage.

I know this sounds simplistic and there probably is something in Squid
that can be "tweaked" .. I just don't agree with the idea that whenever
something goes wrong it's automatically "Squid's fault".


Received on Thu Nov 06 1997 - 16:01:02 MST

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