On Mon, 2011-02-07 at 08:42 +0100, Florian Haas wrote:
> Hello Holger,
>
> that would be excellent functionality to have, thanks very much for the
> contribution! Is there any chance this could be rolled into the existing
> db2 agent? You could use the ocf_is_ms() function to detect whether the
> resource is configured as a master/slave set or as a primitive, and
> based on that determine whether to use HADR or not. Does that sound
> feasible at all?
Hi Florian,
I thought about this as well. Unfortunately I don't consider this
feasible.
Some background:
DB2 has an instance and within the instances databases that can be
activated or not. That means databases can be activated (=started)
individually but they more or less fail or are (forced) shut down
together. Obviously best practice asks for an instance per db in
particular as an instance is pretty lightweight from a resource
perspective.
The existing db2 agent makes an *instance* highly available. As a result
once a *single* database fails the *whole* instance is bounced.
The multipartition support I brought in recently is not available at
all for HADR.
For HADR the situation is different. Ok, the instance must run but
tracking and moving an individual DB through all required state
transitions is the task. Therefore there it has a required parameter
"db" designating the DB at issue and individual commands for stopping
and start HADR are quite different from the standard case.
As conclusion:
1)
Rolling HADR into the existing agent seems impossible to me or
at least will end in a pollution of if and case statement and
over complex logic.
2)
Adding support for a standard database in the one instance / one
db model is feasible. As explained above this will not be
'binary' compatible to the existing agent.
3)
The db2 agent seems to have a long and complex heritage as agent
for different HA solutions or as standalone script so a major
refurbishment is on my To-Do list anyhow.
Moving common code into a helper script as 'library' to be
shared by both agents might be an idea.
Opinions ?
Regards
Holger
>
> Cheers,
> Florian
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