HAST and CARP

[hiroshi at soupacific.com]

Hi Mikolaj!


>
> I don't think resolving split-brain by script is a good idea. You can detect
> split-brain on primary monitoring provider status and then resolve it
> manually. It is much better to have scripts/setup that prevent split-brain
> situations than scripts that resolve it :-)
I agree with you solving split-brain by script.

Today I was thinking about this situation resolving, and conclusion is 
some thing like hastctl role secondary -f xxx
But this command can be used only for emergency situation and not inside 
script.

ifstated is enabled in rc.conf, once reboot ServerB without ServerA 
connection. Such case ServerB became CARP's MASTER then ifstated also 
set hast as primary. This may happen often when setting hast testing time.

So I think some rescue command may help to get out split-brain situation 
caused by any accident or mistake.

>
> You should have a setup so when the master is rebooted after the reboot it
> checks the status of other node and sets its own role accordingly (so there
> would not be two masters simultaneously). Software I use in my setup (our home
> made application) does this well. sysutils/heartbeat should work fine too. As
> for me carp might not do well for this but I am not very experienced with carp
> so I can be wrong.
>

By CARP, ifconfig carp0 advskew {bigger value than secondary} on console 
sets CARP as secondary.

How do you think this idea ?

Hiroshi