[ClusterLabs] Need advice: deep pacemaker integration, best approach?

[Klaus Wenninger]

On Mon, Jun 10, 2024 at 6:12 PM Ken Gaillot <kgaillot at redhat.com> wrote:

> On Sun, 2024-06-09 at 23:13 +0300, alexey at pavlyuts.ru wrote:
> > Hi All,
> >
> > We intend to integrate Pacemaker as failover engine into a very
> > specific product. The handmade prototype works pretty well. It
> > includes a couple of dozens coordinated resources to implement one
> > target application instance with its full network configuration. The
> > prototype was made with pcs shell, but the process is very complex
> > and annoying for mass- rollout by field engineers.
> >
> > Our goal is to develop a kind of configuration shell to allow a user
> > to setup, monitor and manage app instance as entities, not as a set
> > of cluster resources. Means, user deals with app settings and status,
> > the shell translates it to resources configuration and status and
> > back.
> >
> > The shell be made with Python, as it is the best for us for now. The
> > question for me: what is the best approach to put Pacemaker under the
> > capote. I did not consider to build it over pcs as pcs output quite
> > hard to render, so I have to use more machine-friendly interface to
> > pacemaker for sure but the question is which ones fits our needs the
> > best.
>
> pcs, crm shell, and the Pacemaker command-line tools are the basic
> options
>
> > It seems like the best way is to use custom resource agents, XML
> > structures and cibadmin to manage configuration and get status
> > information. However, it is not clean: should cibadmin be used
> > exclusively, or there also other API to pacemaker config pull/push?
>
> If you're using the command-line tools, yes, cibadmin is the interface
> for CIB XML configuration changes. Other tools can perform certain
> configuration changes at a logically higher level (for example,
> crm_attribute can set node attributes in the CIB), but cibadmin can
> handle any XML changes.
>

If you should feel inclined using stuff exposed as C API check out what is
happening in pacemaker 3 (a lot of stuff that was publicly available
moved to private) as you probably don't want to be stuck with 2.1.x.

Klaus


> >
> > Also, it is not clear how to manage resource errors and cleanup? Are
> > there other ways that call to crm_resource for cleanup and failed
> > resource restart? Could it be made via CIB manipulation like force
> > lrm history records delete?
>
> That's what crm_resource --cleanup is for
>
> >
> > I understand that the source is the ultimate answer for any question,
> > but I will be very grateful for any advice from ones who has all the
> > answers on their fingertips.
> >
> > Thank you in advance for sharing your thoughts and experience!
> >
> > Sincerely,
> >
> > Alex
> >
> >
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> --
> Ken Gaillot <kgaillot at redhat.com>
>
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