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Primitives running on multiple hosts

 

 

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Dominik.Epple at EMEA

Mar 27, 2012, 2:17 AM

Post #1 of 2 (353 views)
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Primitives running on multiple hosts

Hello,

I have a primitive resource (in my case, a IPaddr2 simple failover IP). Now I happen to find the resource running on both of the members of the HA cluster. Well, pacemaker says he has started it only on one of the nodes, but the IP address which is managed by this resource is configured on both nodes of the cluster.

Since I don't know what strange events may have lead to this situation (perhaps it was a manual manipulation), I created the following testcase to investigate this: configure a cluster, add some failover IP address primitive resource, let pacemaker start in on one host. Configure this IP address manually on the other host. Hope that pacemaker will detect it and react somehow (stop the resource, or do some stonith, or whatever).

But even with some monitoring op defined, pacemaker seems only to check that the resource is running on the host it is scheduled for, and it does not check that the resource is not running on the host where it should not run. (I verified that the resource agent itself determines the status correctly, i.e. on the started resource, the monitoring action returns 0, on the stopped resource, it returns 7.)

Is this observation correct? Is this the expected behavior? Is it possible to configure the resource such that it is checked that the resource is stopped where it is expected to be stopped?

Regards
Dominik

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Project Home: http://www.clusterlabs.org
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lmb at suse

Mar 27, 2012, 4:29 AM

Post #2 of 2 (350 views)
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Re: Primitives running on multiple hosts [In reply to]

On 2012-03-27T09:17:15, Dominik Epple <Dominik.Epple [at] EMEA> wrote:

> Since I don't know what strange events may have lead to this situation (perhaps it was a manual manipulation), I created the following testcase to investigate this: configure a cluster, add some failover IP address primitive resource, let pacemaker start in on one host. Configure this IP address manually on the other host. Hope that pacemaker will detect it and react somehow (stop the resource, or do some stonith, or whatever).
>
> But even with some monitoring op defined, pacemaker seems only to check that the resource is running on the host it is scheduled for, and it does not check that the resource is not running on the host where it should not run. (I verified that the resource agent itself determines the status correctly, i.e. on the started resource, the monitoring action returns 0, on the stopped resource, it returns 7.)
>
> Is this observation correct? Is this the expected behavior? Is it possible to configure the resource such that it is checked that the resource is stopped where it is expected to be stopped?

Pacemaker will explicitly check for resources being active on start-up
on a node (we call that particular call to monitor "probe").

After that, we don't expect admins to manually mess things up. ;-)

You can, however, configure an explicit monitor for role="Stopped",
which will be able to detect primitives that are active where they
shouldn't be (within the configured interval). Yan added that on my
request for feature parity with another well-known cluster solution.

That will eventually catch them, but of course, if it really matters,
you'll already be looking at data/service corruption in the meantime.



Regards,
Lars

--
Architect Storage/HA
SUSE LINUX Products GmbH, GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer, HRB 21284 (AG Nürnberg)
"Experience is the name everyone gives to their mistakes." -- Oscar Wilde


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Project Home: http://www.clusterlabs.org
Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf
Bugs: http://bugs.clusterlabs.org

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