[ClusterLabs] Coming in Pacemaker 2.1.0: OCF resource agent path

[Andrei Borzenkov]

On 20.05.2021 00:33, kgaillot at redhat.com wrote:
> Hi all,
> 
> We squeezed one more feature into the Pacemaker 2.1.0 release for rc2:
> the ability to search multiple directories for OCF resource agents.
> 
> Previously, the OCF root (typically /usr/lib/ocf) could be specified at
> build time via ./configure --with-ocfdir, and all resource agents had
> to be in the resource.d directory below that.
> 
> Now, the configure script will have three related options:
> 
> * --with-ocfdir: This establishes the OCF_ROOT variable that is passed
> to resource agents, which is used to find the ocf-shellfuncs include
> files.
> 
> * --with-ocfrainstalldir: This specifies where the ocf:pacemaker
> resource agents will be installed.
> 
> * --with-ocfrapath: This is a colon-separated path of directories that
> will be searched for OCF resource agents (like PATH for agents).
> 
> All default to values provided by the resource-agents package, if
> available. Otherwise, they default to the current behavior.
> 
> Example:
> 
> ./configure --with-ocfdir=/usr/libexec/ocf \
>   --with-ocfrapath=/usr/libexec/ocf/resource.d:/usr/lib/ocf/resource.d:/srv/ocf/resource.d
> 
> The above will define the OCF_ROOT as /usr/libexec/ocf instead of the
> usual /usr/lib/ocf. The ocf:pacemaker agents will be installed in
> /usr/libexec/ocf/resource.d (via default).
> 
> When a resource agent needs to be executed, Pacemaker will search in
> three locations: first, /usr/libexec/ocf/resource.d, and if not found
> there, /usr/lib/ocf/resource.d, and if not found in either location,
> /srv/ocf/resource.d.
> 

The agent name must still be unique across all directories? Is it
possible to explicitly refer to /srv/ocf/resource.d?

Will pacemaker print search path on startup or how it possible to query
it at runtime?

Will pacemaker print full path to resource agent in logs? Because now
actual agent binary may change from invocation to invocation - consider
path /override/ocf/resoyrce.d:/usr/libexec/ocf/resource.d. If I drop
binary into /override and restart pacemaker it will use new binaries,
correct?

When path is searched - on every invocation of agent or once on startup?
Can I change binary without restarting pacemaker?


> An example use case might be installing custom agents beneath /srv to
> keep them separate from OS-provided agents. Or, agents installed in
> various temporary directories for Continuous Integration (CI) testing.
> Or, a third-party provider installing agents beneath /opt.
> 
> In the 2.1.0 release, the path will be a build-time option, for
> simplicity. If there is demand, it should be possible to make it a run-
> time option, but that would have some drawbacks, so we're currently not
> planning to.
>