Mailing List Archive: [mod_backhand-users] backhand configuration (2 httpd's on one system)

I am having problems with the following 2 machine configuration:

1) "light" httpd listening on port 80 of the external IP and 10.0.0.99
2) mod_perl enabled httpd on the same server, listening on ports 8001-8003
of 10.0.0.1 and 127.0.0.1
3) mod_perl enabled httpd on a second server, listening on ports 8001-8003
of 10.0.0.2

mod_backhand-1.1.1pre4 configuration:

httpd 1:
UnixSocketDir /var/run/backhand
MulticastStats 10.0.0.99 10.0.0.255:4445
AcceptStats 10.0.0.0/24

httpd 2:
UnixSocketDir /var/run/backhand-fat (same machine as httpd 1!)
MulticastStats 10.0.0.1 10.0.0.255:4445
AcceptStats 10.0.0.0/24

httpd 3:
UnixSocketDir /var/run/backhand
MulticastStats 10.0.0.2 10.0.0.255:4445
AcceptStats 10.0.0.0/24

The basic idea is to distribute requests to the 2 "fat" httpd's from the
light httpd. However, backhand-status reports:
httpd1: httpd1 (10.0.0.99:80) and httpd3 (10.0.0.2:8003) visible
httpd2: nothing visible!
httpd3: httpd3 (10.0.0.2:8003) visible

Any ideas? This logfile excerpt from httpd2 looks suspicious:

[Fri Mar 23 16:29:38 2001] [notice] backhand_init(33916) spawning moderator
(PID 3260)
[Fri Mar 23 16:29:38 2001] [notice] mod_backhand moderator ready to go
[Fri Mar 23 16:29:38 2001] [notice] Apache/1.3.19 (Unix)
balanced_by_mod_backhand/1.1.1pre4 mod_perl/1.24 configured -- resuming
normal operations
[Fri Mar 23 16:29:38 2001] [warn] long lost child came home! (pid 3260)

It would be extremely useful if the mod_backhand web pages contained some
sort of repository with examples of common, working configurations ... (the
examples in the FAQ are useful, but don't cover many cases)

Thanks,
Marinos
--
Marinos J. Yannikos
Preisvergleich Internet Services AG, Linke Wienzeile 4/2/5, A-1060 Wien
Tel/Fax: (+431) 5811609-52/-55

This is a limitation of mod_backhand. It currently will not allow you to run
two mod_bachand enabled Apache servers on the same machine with the same
broadcast port -- and yes, they have to have the same port to see each other.

Solutions. Don't run mod_backhand on httpd 2 and the multicast stats line for
httpd 1 should be MulticastStats 10.0.0.1 10.0.0.255:4445.

This will cause thttpd 1 to advertise itself as if it were httpd 2.

Also use: "BackhandSelfRedirect On"

So effectively, the front end server will not see "itself" for rather the two
backend servers. This is fine because one of the back end servers is on the
same machine.

Also, 10.0.0.255 isn't the standard IP broadcast address. The 10 network is,
by default, a /8 on most systems. Be sure that you have explicitly set you
broadcast to 10.0.0.255 and your netmask to 0xff000000 as be default it will
be something else.

"Marinos J. Yannikos" wrote:
> I am having problems with the following 2 machine configuration:
>
> 1) "light" httpd listening on port 80 of the external IP and 10.0.0.99
> 2) mod_perl enabled httpd on the same server, listening on ports 8001-8003
> of 10.0.0.1 and 127.0.0.1
> 3) mod_perl enabled httpd on a second server, listening on ports 8001-8003
> of 10.0.0.2
>
> mod_backhand-1.1.1pre4 configuration:
>
> httpd 1:
> UnixSocketDir /var/run/backhand
> MulticastStats 10.0.0.99 10.0.0.255:4445
> AcceptStats 10.0.0.0/24
>
> httpd 2:
> UnixSocketDir /var/run/backhand-fat (same machine as httpd 1!)
> MulticastStats 10.0.0.1 10.0.0.255:4445
> AcceptStats 10.0.0.0/24
>
> httpd 3:
> UnixSocketDir /var/run/backhand
> MulticastStats 10.0.0.2 10.0.0.255:4445
> AcceptStats 10.0.0.0/24
>
> The basic idea is to distribute requests to the 2 "fat" httpd's from the
> light httpd. However, backhand-status reports:
> httpd1: httpd1 (10.0.0.99:80) and httpd3 (10.0.0.2:8003) visible
> httpd2: nothing visible!
> httpd3: httpd3 (10.0.0.2:8003) visible
>
> Any ideas? This logfile excerpt from httpd2 looks suspicious:
>
> [Fri Mar 23 16:29:38 2001] [notice] backhand_init(33916) spawning moderator
> (PID 3260)
> [Fri Mar 23 16:29:38 2001] [notice] mod_backhand moderator ready to go
> [Fri Mar 23 16:29:38 2001] [notice] Apache/1.3.19 (Unix)
> balanced_by_mod_backhand/1.1.1pre4 mod_perl/1.24 configured -- resuming
> normal operations
> [Fri Mar 23 16:29:38 2001] [warn] long lost child came home! (pid 3260)
>
> It would be extremely useful if the mod_backhand web pages contained some
> sort of repository with examples of common, working configurations ... (the
> examples in the FAQ are useful, but don't cover many cases)

--
Theo Schlossnagle
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