portforwarding to avoid downtime on apache-restart

the problem is that I have an application (mod_perl) that preloads huge
datastructures on serverstartup (500MB) to have it easily shared between
the forked apache-threads later. This is very efficient and convient,
cause all threads share the same datastructure and can access pretty fast.

Now the problem is, that a change in the datastructure means that I need
to restart apache to reload the datastructure. Shutting down and
restarting the server takes about 20seconds (the dataloading takes its
time) and in that time the server is offline which is something I would
like to avoid.

So how can I deal with this?

One solution would be to have apache listen on a different port and
portforward 80 to this port. On reload I first start a new apache on
another port. When its up I change the portforward to this port and then
I shut down the old apache. This would mean some swapping on the server,
cause 500MB are not taken that easily but it would work.

The other solution would be to have the clients "waiting" during the
20s-reboot of apache. They should merely timeout, but be disconnected.
How could I do this? As soon as apache is down, the client tell me that
there is no server instead of waiting and waiting ...

thnx for any idea, recommandation ...
peter




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> the problem is that I have an application (mod_perl) that preloads huge
> datastructures on serverstartup (500MB) to have it easily shared between
> the forked apache-threads later. This is very efficient and convient,
> cause all threads share the same datastructure and can access pretty fast.
>
> Now the problem is, that a change in the datastructure means that I need
> to restart apache to reload the datastructure. Shutting down and
> restarting the server takes about 20seconds (the dataloading takes its
> time) and in that time the server is offline which is something I would
> like to avoid.
>
> So how can I deal with this?

We have an application which needs to pre-load, pre-process, and
pre-compute large amounts of data as well, and we made it a standalone
daemon which listens for requests on a unix socket. That way, restarts of
Apache don't affect it at all, and here's the good part: If we need to
restart the daemon, we can start a new one first, let it do the
pre-processing, then kill the old one.

steve