On Wed, 2021-04-28 at 18:14 +0200, Jehan-Guillaume de Rorthais wrote: > Hi all, > > It seems to me the concern raised by Ulrich hasn't been discussed: > > On Wed, 12 Apr 2021 Ulrich Windl wrote: > > > Personally I think an RA calling crm_mon is inherently broken: Will > > it ever > > pass ocf-tester?
Calling the command-line tools in an agent can be OK in some cases. The main concerns are: * Time-of-check/time-of-use: cluster status can change immediately, so the agent should behave reasonably if a query result is incorrect at the moment it's used. Ideally there would be no case where the agent could incorrectly report success for an action. * No commands that *change* the configuration (other than setting node attributes) should ever be used. Otherwise there's a potential for an infinite loop between the agent and scheduler. * It's best to use tools' XML output when available, because that should be stable across Pacemaker releases, while the text output may not be. Aside from crm_mon, XML output is a recent addition, so some consideration must be given to backward compatibility and/or requiring a minimum Pacemaker version. * Only the configuration section of the CIB has a guaranteed schema. The status section can theoretically change from release to release, although in practice it has changed very little over the years. I don't use ocf-tester so I can't speak to that, but I suspect it could work if you exported a CIB_file variable with a sample cluster status beforehand. (CIB_file makes the cluster commands act as if the specified file is the live CIB at the moment.) > Would it be possible to rely on the following command ? > > cibadmin --query --xpath "//status/node_state[@join='member']" | \ > grep -Po 'uname="\K[^"]+' > > > Regards, Only full cluster nodes will have a "join" attribute, so that query won't catch active remote nodes or guest nodes. Whether that's good or bad depends on what you're looking for. The plus side is that it's a query and it returns XML. The downsides are that node status can change quickly, so it could theoretically be inaccurate a moment later when you use it, and the status section is not guaranteed to stay in that format (though I expect that particular part will). A minor point: that query will return the entire node_state XML subtree; you can add -n/--no-children to return just the node_state element itself. -- Ken Gaillot <kgail...@redhat.com> _______________________________________________ Manage your subscription: https://lists.clusterlabs.org/mailman/listinfo/users ClusterLabs home: https://www.clusterlabs.org/
