I would also check the syslog for any backends timing out on requests, that would push users to another backend. Also, if you have run out of file descriptors you would surely see "too many open files"

 

By the way it's also worth mentioning that if you don't solve this problem through pound, there is another solution which is to implement session replication accross your backend - then you would also never lose a session even if that backend timed out or went down.

 

/David

 

On 10/29/05, Russell Valentine <russ@altec.org> wrote:

Ohh sorry, yes I use session type of "IP". After I sent the email I
noticed I was reading the log files wrong and that the file descriptor
and thread count was not representative when we would see the problem.
So far I hadn't seen the problem since I've been keeping track of that
(two days). We get more load the beginning of the week, so I'll get new
numbers including request rate at that time.

Since you apparently seem to not have any problems if I don't find some
obvious solution then (like file descriptors) then I'll recheck the
application, however it was two separate applications that had been
observed to have this happening.

Thanks for your reply!


Russell Valentine

david walters said the following on 10/28/2005 12:52 PM:
>
> You don't mention what kind of session affinity you have configured... I
> only mention this because your key problem seems to be with session
> affinity - and pound offers several types...
>
> Personally I would think that a session type of "IP" (because a hashed
> lookup should be the fastest) would be a reasonable compromise for high
> performance against equal balance in order handle peak loads the best on
> a modest server.
>
> The drawback is "if" you have lot of users from a single IP, then your
> cluster will not be 'perfectly' balanced. i.e. some backend servers will
> have to handle more load than others.
>
> We have 10 times your traffic _average_ by the way on a _very_ modest
> (single CPU) server and no problems whatsover :-)
>
> /David
>
>
> On 10/28/05, *Russell Valentine* <russ@altec.org
> <mailto:russ@altec.org>> wrote:
>
>     Hi, I've been using pound for about two years, thanks for the great
>     program. I have a question concerning sessions. I've been noticing
>     during our busiest times it seems after a certain point pound can't
>     remember new sessions anymore, so new sessions cannot be maintained on
>     the web server.
>
>     1) User hits pound
>     2) pound sends request to certain backend
>     3) session gets made on backend
>     4) user hits pound again
>     5) pound sends request to a different backend, now backend has no idea
>     about the session
>
>     I only see this problem during times when we have most of our traffic,
>     when we get around 1000 requests per minute.
>
>     I tried to see if we were perhaps maxing on threads or file descriptors.
>     I counted the treads with ps and used lsof for file descriptor and
>     counted those periodically in a cron job.
>
>     Max I see from lsof: ~200
>     Max # of threads I see is ~100
>
>     These are no where near the limit as shown in ulimit.
>     I'm using pound v1.9 on Linux 2.4 kernel. Does anyone have ideas?
>
>
>     Russell Valentine
>
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> --
> Regards,
> David Walters


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