[Pacemaker] Dependency Trees

[Jake Smith]

----- Original Message -----
> From: "Donald Stahl" <don at blacksun.org>
> To: "Jake Smith" <jsmith at argotec.com>, "The Pacemaker cluster resource manager" <pacemaker at oss.clusterlabs.org>
> Sent: Thursday, February 21, 2013 2:24:59 PM
> Subject: Re: [Pacemaker] Dependency Trees
> 
> > I think you may have missed a key piece - Sets.  Requires more than
> > 2 and assumes at least one will be sequential.
> 
> Not exactly. That may have been a poor example but what I was trying
> to achieve was the idea that these 2 services must run on the same
> host, but that neither one had to be running, or placed, first.
> 

I get what your trying for - I was more responding to your example.  And I *may* be wrong about requiring more than 2 w/one sequential.

> For example- if I create the following:
> 
> colocation OraLsnr03 inf: OraData3 OraBin3 OraIP3
> 
> # crm_mon -r --one-shot
>  OraData3       (ocf::heartbeat:Filesystem):    Started Host-A
>  OraBin3        (ocf::heartbeat:Filesystem):    Started Host-A
>  OraIP3 (ocf::heartbeat:IPaddr2):       Started Host-A
> 
> All three services are running. But now- if I shut down OraData3:
> 
> # crm resource stop OraData3
> # crm_mon -r --one-shot
>  OraData3       (ocf::heartbeat:Filesystem):    Stopped
>  OraBin3        (ocf::heartbeat:Filesystem):    Stopped
>  OraIP3 (ocf::heartbeat:IPaddr2):       Stopped
> 
> All three services are shut down. If I start OraData3- then all three
> resources start back up.
> 
> That was not the behavior I needed because there is a sort of implied
> order.
> 
> What I needed to do was put them in ()'s which sets sequential=false
> in the XML.
> 
> When I do that- I can stop and start individual services without
> affecting the other ones.
> 
> In short- I needed to be able to say:
> 
> These three services must always run on the same host- but not
> necessarily started.
> 
> Or perhaps more accurately- If any one of these services is running
> on
> a host- then the other related services must either be running on the
> same host _or_ not running at all.
> 
> colocation OraLsnr03 inf: \( OraData3 OraBin3 OraIP3 \)
> 
> Creates the behavior I have just described.

That's great - just to be sure it works as you expect did you try migrating/starting one of the resources on the other node and make sure the others didn't come up on the first node?

Jake

> 
> colocation OraLsnr03 inf: OraData3 OraBin3 OraIP3
> 
> Creates the dependency and ordering behavior I did not want.
> 
> > Here might explain better - have a look at the "Unversioned Docs"
> > at 'General Concepts' - ordering explained and colocation
> > explained.  Well into each of the documents they talk about
> > sequential/non-sequential:
> >
> > http://clusterlabs.org/doc/
> I will give this a more thorough read but I believe I finally have my
> head straight.
> 
> Thanks for all of the insight.
> -Don
> 
>