Re: [squid-users] running out of file descriptors (SOLVED!)

fre 2003-04-04 klockan 18.20 skrev Mike Rambo:

> There are three UW SCSI3 drives in the machine. One 18GB drive is
> dedicated to the cache. It is formatted reiser fs.

You might want to add a second cache drive in the long run..

> > You can also try the following settings to reduce the amount of
> > filedescriptors used:
> >
> > half_closed_clients off
> >
> > And if that does not help
> >
> > server_persistent_connections off
> >
> > and finally if still a problem
> >
> > client_persistent_connections off
>
> I tried all three of these. The first had no discernible effect. I tried
> both of the _persisent_connections options this morning together. This
> has been a HUGE win. The file descriptors problem went away and
> interactivity (read speed of access to web pages) has went up very, very
> noticeably. I can't hardly believe how much faster it's running. I
> noticed the requests per second we're servicing has went up by at least
> 25% and really it's up almost by a third. We're no longer showing
> anywhere near full useage of file descriptors - the vast majority are
> free.
>
> Is there a downside to these changes? Are there any other things I need
> to be on the alert for now that I've made them?

The first one has no negative effects for browsers. Basically only
people trying to fetch HTTP via scrips using telnet or netcat see any
difference from this one.. and when off Squid can immediately detect
when a client aborts a request and tear down the connection. This makes
a huge difference if there is problems reaching some frequently used web
sites (or if you have a virus/worm which successfully makes it via the
proxy hitting random targets..)

The other two are an optimization of the HTTP protocol to avoid
repetition the TCP handshake overhead on each request by keeping
connections open. But as you may have discovered, Squid is not very
clever in getting rid of unused such connections before they expire when
running short of filedescriptors (Bug #571).. Normally performance is
slightly increased by having these on (maybe 10% reduction in latency),
but if you run short of filedescriptors then the direct opposite effect
is seen due to the filedescriptor shortage making Squid no longer accept
new connections..

Regards
Henrik

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