[ic] question on mod_interchange socket closing (different fromprevious question)

[interchange-users@icdevgroup.org (Kevin Walsh)]

John Young [john_young@sonic.net]
> >
> > Well, that's the idea.  Mod_interchange also has failover support for
> > clustered environments, allowing Interchange to be taken offline on one
> > machine while still allowing mod_interchange, on the same machine, to
> > process requests via another machine.  It's not a lot of use, except if
> > Interchange fails for some reason, but it's a start.
> >
> But perhaps a round-robin load-balancing option might be...
> 
> That's something I was thinking of a while ago in looking over your
> mod_interchange code (and futiley struggling to write an Apache v2 mod
> without documentation or C programming experience).  I'm thinking that it
> would only be minor changes to perhaps:
> 
> * Have a config setting in httpd.conf of RoundRobin or somesuch,
>   and list the hosts to be used (sort of like InterchangeServerBackup
>   in a list context).
> * Mod_interchange would just cycle through that list of hosts as
>   it processed requests.
> 
> You could even introduce some sort of weighting factor if you wanted
> to get clever, whereby hostA is handed twice as many requests as
> hostB, or whatever.  Of course, it would be sweet if mod_ic was able
> to determine server load a little more dynamically.  While I hate to see
> application bloat, in this case I wonder about an IC config setting enabling
> IC to reply to mod_interchange with a load average (like w provides),
> and mod_interchange responding to that load average by dynamically
> adjusting this proposed weighting factor.
> 
> The round-robin idea, even if static, might be a neat little enhancement.
> That, combined with mod_interchange's existing ConnectTries and
> ConnectRetryDelay, would be pretty good.  I'm not sure about session,
> logging, and other issues, though.  And I worry about adding latency
> for something that might only be useful in rare circumstances.
> 
> I'll be away until Friday, but I look forward to hearing what you think
> about this.
> 
Mod_interchange is most efficient when using a UNIX mode socket to the
local Interchange server.  I only coded support for one failover to
allow for temporary local downtime; perhaps for upgrades etc.

There could be a list of backup servers, but I didn't feel that it was
necessary.  Mod_interchange's failover support wasn't designed to be a
substitute for proper clustering technology.  If the local server is
down, as well as its designated secondary, then there's something very
wrong that's in need urgent attention.

>
> Thanks for keeping mod_interchange in top shape, Kevin!
> 
No problem.  I'm just glad that there are a couple of people who find
it useful.

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