On Tue, Jun 21, 2005 at 10:04:13AM -0400, Vivek Khera wrote:
> 
> On Jun 20, 2005, at 2:21 PM, 31337 .. wrote:
> 
> >Are there any other easier ways to detect when the master node has  
> >gone down?
> 
> Your first step is to define *precisely* what you consider "down".   
> Try enumerating all scenarios relative to each machine that could be  
> connecting to any of your db servers, and how you would notify all of  
> those hosts to switch to another "master", and how you would tell the  
> master it is no longer the master should it become undead.
> 
> This will be very hard.

You might want to take a look at the capabilities offered by a project
such as Linux HA (www.linux-ha.org) or the Red Hat Cluster Suite. There
are many failure & failover scenarios & you don't really want to have
thing of them all yourself, so better to leverage existing code. Ultimately
the real key to a reliable failover is some sort of STONITH (Shoot The
Other Node In The Head) capability to ensure that, when a failover 
occurrs, there is absolutely no way the original master can come back 
to life. Hardware power switches are the preferrable, but software
NMI watchdogs could be used to do an automatic reboot of the failed
node. The Linux-HA / RH Cluster Suite agents, also take care of issues
such as quorum & split-brain to ensure optimal choice of slave to fail
over too.

Regards,
Dan.
-- 
|=-            GPG key: http://www.berrange.com/~dan/gpgkey.txt       -=|
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|=-   berrange at redhat.com  -  Daniel Berrange  -  dan at berrange.com    -=|
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