Re: {bb} failover configuration

[Philip Clark <bblist@cannae.uklinux.net>]

On Mon, 2006-08-28 at 23:13, steve sayler wrote:

> Hello brother(s) and sister(s);
>
> I'm setting up my server(s) for failover. While looking back through
> the archives, I see to see a mix of various documentation on failover
> configuration. While I'm setting up my server(s) initially, I'm
> trying to document everything (an ambitious idea, heh?). I'd like
> your feedback on my document detailing the Big Brother failover
> configuration. Here it is:
>
>
>   Big Brother Failover:
>
>   The Big Brother 'failover' service watches bb variables;  BBNET and
>   BBPAGER.  Big Brother BBNET is the Big Brother Network monitoring
>   machine/server, and BBPAGER is the machine/server that handles
>   notifications. A failover occurs whenever either the primary BBNET
>   or BBPAGER server become unavailable. The alternate/failover machine
>   takes over until the primary machine/server become available.
>
>   Configuration:
>
>   1). Add failover to the BBEXT variable in etc/bbdef.sh on the
>   failover server. 
>
>   Change BBEXT="" to BBEXT="failover" on the failover server.
>
>   2). Define both the primary and failover machines as BBPAGERS in
>   etc/bb-hosts
>
>   primary's etc/bb-hosts:
>   xxx.xxx.xxx.xxx primary # BBPAGER BBNET BBDISPLAY
>   yyy.yyy.yyy.yyy failover # BBPAGER
>
>   failover's etc/bb-hosts  (note: all machines should have identical
>   etc/bb-host files):
>   xxx.xxx.xxx.xxx primary # BBPAGER BBNET BBDISPLAY
>   yyy.yyy.yyy.yyy failover # BBPAGER
>
>   BBNET failover is automatic when we can't reach the BBNET machine.
>   BBNET should only be defined ONCE in the bb-hosts file, and should
>   not be defined on the failover machine. However, if the BBNET
>   machine is also your primary BBPAGER, then it best to have BBNET
>   failover when BBPAGER failsover. This is our case.
>  
>   3). It is useful to detect the situation when the BBNET machine is
>   still reachable but BBNET isn't working because someone turned BB
>   off... To enable this behavior, uncomment the following line
>   inext/failover  on the failover machine:
>
>   # FAILOVERBOTH=TRUE         # FAILOVER BBNET WITH BBPAGER

I see no errors so far, but you may like to add some a few items
just to make it a little clearer.

The failover script can also be defined in the bb-bbexttab file,
instead of bbdef.sh. This is the more modern way to do things and,
if you have multiple scripts running, might be less confusing.

The rule of "identical bb-hosts everywhere" has some limitations.
There are situations where it is necessary to use different files
on different machines. Unless you need a more complex installation
however, it is strongly recommended that you obey the rule.
Similarly with BBNET definition, it is possible to run more than
one. The point is that, on a failover BBNET server, this directive
should not be specified.

The reason for this is that BBNET and BBPAGER failover work in
slightly different ways. If the failover machine is handling both
functions, it runs the BBPAGER process even when the primary is
operational. That process is in a "standby" state and simply
discards any paging requests. For that reason, you also need to
change "bbwarn:" in bbwarnsetup.cfg to something other than TRUE.
Also, the script triggers BBPAGER failover by testing the
operation of the primary. It attempts to send a dummy page to
the primary and steps in if that fails.

Where BBNET is concerned, the failover machine does not run the
process when the primary is up. The script just tests that it can
ping the primary and will start the BBNET process if the primary
disappears. The FAILOVERBOTH option changes this behaviour so that
BBNET will start when the primary BBPAGER fails, even if the host
can still be pinged. 

Cheers, Phil.



-- 
Positive, adj.: Mistaken at the top of one's voice.
(Ambrose Bierce, "The Devil's Dictionary")

--
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-==-=-=-=-=-=-=-=-=-=-=-=
To unsubscribe from this list, or to subscribe to the bb-digest list
send e-mail to mailto:majordomo@bb4.com with unsubscribe bb -and/or-
subscribe bb-digest in the BODY of the message.