[Linux-ha-dev] Ordering of OCF Start, Stop and Monitor actions

[Doug Knight]

Yes, Thanks Alan. Let me digest it, and walk through my OCF script. I'll
see if I have any other questions after that.

Thanks for getting back to me.

Doug

On Wed, 2007-03-14 at 11:41 -0600, Alan Robertson wrote:
> Doug Knight wrote:
> > Hi All,
> > I currently am running a two node cluster (host1 and host2) with version
> > 2.0.8. I have a resource defined with a place constraint of "#uname eq
> > host1", so that it will start on host1 (using an OCF RA script,
> > including all of the required methods). The resource itself has
> > target_role set to "stopped".
> > 
> > Question 1: Is the monitor method called regularly on both nodes to make
> > sure the resource is not running?
> 
> No.  It is called on every node when we first start up (we call it a
> probe operation).  If you ask us to, we will run it periodically to
> ensure that a running copy continues to run.
> 
> You can also manually request to run this initial probe again to catch
> errors made by system administrators (but I don't know of anyone who
> does that).
> 
> 
> > Next, I change the target_role to "started" (i.e. I use the GUI and
> > click the start button).
> [Better yet, use the "outline" start button]
> 
> > Question 2: What is the order of OCF methods called to bring up the
> > resource? Is Monitor called before Start on host1? Does Stop and/or
> > Monitor ever get called on host2?
> 
> Monitor gets called when we first start up on every node.
> It also get called repeatedly on any node that we think is running it --
> if you ask us to monitor the resource.
> 
> > Resource is up and running on host1, and I decide to move the resource
> > to host2. I click the constraint and change it to "#uname eq host2". The
> > resource stops on host1 and starts on host2.
> > 
> > Question 3: Same idea, what are the sequence of method calls to migrate
> > the resource from host1 to host2?
> 
> In the past...
> 	monitor every resource on every node once to see what's already
> 		running
> 	start on "some node"
> 	monitor periodically on "some node" (if requested)
> 
> Request to move resource arrives...
> 	stop monitoring on "some node" (if it had been requested)
> 	stop resource on "some node"
> 	start resource on "some other" node
> 	monitor periodically on "some other node" (if requested)
> 
> > I'm trying to thoroughly understand the sequence of events that occurs
> > for each phase in support of the Postgres WAL file forwarding
> > configuration I posted last week ("[Linux-HA] Two node cluster with
> > Postgres in WAL file fwding mode", started March 1).
> 
> 
> Does that help?
> 
> 
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