[Pacemaker] Dependency Trees

[Andrew Beekhof]

On Thu, Feb 21, 2013 at 3:06 PM, Donald Stahl <don at blacksun.org> wrote:
>> On the one hand, you say OraListener1 and OraInstance1 need to be on
>> the same node, but on the other you say they can start/stop
>> individually.
>
> There are maintenance reasons for some of these requirements- for
> example the listener can only ever be on the same box as the database,
> but I might want to take the listener down but keep the database up. I
> realize it's an odd requirement.
>
>> I hadn't read that part so closely when I said "shouldn't be too hard"
>> and indeed that is hard for us to express.
>> In Pacemaker, either A needs B or it doesn't.
> Fair enough. I'm not the database guy so I've been asked to replicate
> this VCS configuration as closely as possible. At the same time- I
> want to understand pacemaker as well as I can. I appreciate your
> feedback.
>
>> Other than that, you seem to want:
>>
>> order OraInstance1 OraBin1
>> order OraInstance1 OraData1
>>
>> order OraListener1 OraBin1
>> order OraListener1 OraData1
>> order OraListener1 OraIP1
>>
>> Do OraInstance1/OraListener1 need to live on the same host as OraBin1/OraData1 ?
>> If so, you can get the behaviour you're after by adding something like:
>>
>> colocate OraInstance1 OraBin1
>> colocate OraListener1 OraBin1
>> colocate OraBin1 OraData1
>>
>> So OraInstance1 and OraListener1 can go up/down individually but
>> always on the same host as OraBin1/OraData1.
>> Also, if OraBin1 or OraData1 go down they'll take OraInstance1 and
>> OraListener1 with them.
>>
>> Is that close?
> That is exactly what I am trying to accomplish. I started to think
> along those lines after your previous email (and doing a little more
> reading) but I hadn't gotten there.
>
> The only part I'm not clear on is - doesn't:
>> colocate OraListener1 OraBin1
>
> imply:
>> order OraListener1 OraBin1
> ?

No.

[quote]
If you say "colocate A with B" and there is nowhere B is allowed to
run, then A wont be allowed to run either.
But once the cluster has figured out where they go, it doesn't stop
them being started in parallel.
[/quote]

in this case, A = OraListener1 and B = OraBin1

You only get the "Start A then start B" part by adding the ordering constraint.

> Or to put it another way- I'm not sure I understand the difference between:
> colocate OraListener1 OraBin1
>
> and:
> colocate (OraListener1 OraBin1)
> order OraListener1 OraBin1
> ?
>
> Regardless of the answer- I should be able to get the config set up
> the way I need. Thanks again for all of the help.
>
> -Don
>
> _______________________________________________
> Pacemaker mailing list: Pacemaker at oss.clusterlabs.org
> http://oss.clusterlabs.org/mailman/listinfo/pacemaker
>
> Project Home: http://www.clusterlabs.org
> Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf
> Bugs: http://bugs.clusterlabs.org