[ClusterLabs] Required guidance w.r.t pacemaker

[Sridhar K]

Got it, Ken, Thanks a lot for the timely help, proceeded with the setup,
will complete and test the HA part

Thank you all once again, :)
Good Day!!

regards
Sridhar

On Wed, 8 Jun 2022 at 21:19, Ken Gaillot <kgaillot at redhat.com> wrote:

> On Wed, 2022-06-08 at 20:28 +0530, Sridhar K wrote:
> > Thanks a lot, Ken,Andrie for the time and guidance it was really
> > helpful.
> >
> > will proceed with the below approach
> >
> > [A preferred setup would be to run corosync and pacemaker on the VMs,
> > and configure bundles for the db containers.]
> >
> > I will try to get comfortable with bundle approach , referring
> > https://wiki.clusterlabs.org/wiki/Bundle_Walk-Through
> >
> > In above link, it's said at the start [Configure a test cluster of at
> > least two cluster nodes with Pacemaker 1.1.17 or later]
> > but in the section
> > Configure the cluster
> >  Our example needs the run-command option only because we are running
> > Pacemaker 1.1 inside the container:
> >
> > In short, we have a pacemaker cluster with 2 nodes(i,e full stack
> > pacemaker installed) and a bundle that has a  docker/podman image the
> > image has only pacemaker-remote installed in it.
> > i,e Line
> > RUN yum install -y httpd bind-utils curl lsof wget which pacemaker
> > pacemaker-remote resource-agents
> > Is my understanding correct, or in the image built we have a full-
> > stack pacemaker as well.
>
> You at least need the pacemaker-cli package as well.
>
> The container will only run pacemaker-remoted, but it's worthwhile to
> install the full pacemaker package because it has ancillary files that
> are useful.
>
> (In the just-released 2.1.3 version, the crm_attribute tool is now in
> the pacemaker-cli package, so that is not as big a deal anymore.)
>
> >
> > In case of any other links w.r.t usage of bundle/examples, Please
> > share the same.
>
> The walk-through is a good start. For fuller details, see:
>
>
> https://clusterlabs.org/pacemaker/doc/2.1/Pacemaker_Explained/singlehtml/index.html#bundles-containerized-resources
>
> >
> > Regards
> > Sridhar
> >
> >
> > On Wed, 8 Jun 2022 at 19:46, Andrei Borzenkov <arvidjaar at gmail.com>
> > wrote:
> > > On 08.06.2022 17:01, Ken Gaillot wrote:
> > > > On Wed, 2022-06-08 at 18:31 +0530, Sridhar K wrote:
> > > >> Hi Team,
> > > >>
> > > >> Required guidance w.r.t below problem statement
> > > >>
> > > >> Need to have a HA setup for SQLServer running as a docker
> > > container
> > > >> and HA managed by the Pacemaker which is running as a separate
> > > docker
> > > >> container.
> > > >>
> > > >> I have done a setup where pacemaker and SQL Server are running
> > > as a
> > > >> single docker container, able to achieve HA.
> > > >>
> > > >> How to achieve the same when Pacemaker , and Sqlserver are
> > > running in
> > > >> different containers.
> > > >
> > > > I suspect it's not feasible.
> > > >
> > > > At a minimum, the Pacemaker container needs to run corosync as
> > > well as
> > > > pacemaker (implying a custom pid 1 script that starts both) and
> > > needs
> > > > to be privileged. I'm not sure corosync has been successfully
> > > > containerized before.
> > > >
> > > > Bundles won't work because they can only run on Pacemaker nodes.
> > > >
> > > > The db container could be configured as a remote node, basically
> > > > reproducing how a bundle is created internally. The db container
> > > would
> > > > be configured with pacemaker-remoted as its pid 1, and an IP
> > > given to
> > > > it that both pacemaker containers can reach. Launching all the
> > > > containers would need to be done by the OS at boot or manually.
> > > >
> > > > An ocf:pacemaker:remote resource would be configured in the
> > > cluster to
> > > > allow the pacemaker containers to manage the db via pacemaker-
> > > remoted
> > > > in the db containers.
> > > >
> > > > A custom fence agent would be needed to allow a pacemaker
> > > container to
> > > > ask the VM to reboot (kill and relaunch) any other container.
> > > Each VM
> > >
> > > Actually there is fence_docker which should work in this case.
> > >
> > > > and VM host would become a single point of failure unless a
> > > pacemaker
> > > > container could fence the VM and then the host as fallback fence
> > > > mechanisms in a topology.
> > > >
> > > > E.g. try to fence the container -> if that fails, try to fence
> > > the VM
> > > > -> if that fails, try to fence the host. Without all of that
> > > working,
> > > > something becomes a single point of failure.
> > > >
> > > > A preferred setup would be to run corosync and pacemaker on the
> > > VMs,
> > > > and configure bundles for the db containers.
> > > >
> > > >>
> > > >> Checked remote node,bundle  concepts in Pacemaker unable to make
> > > HA
> > > >> setup work.
> > > >>
> > > >> Please let me know whether the above scenario can be handled,
> > > any
> > > >> links, examples would be of great help.
> > > >>
> > > >> Attaching a picture that depicts the scenario.
> > > >>
> > > >> Please do the needful, Thank you
> > > >>
> > > >> Regards
> > > >> Sridhar
> > > >
> > >
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> --
> Ken Gaillot <kgaillot at redhat.com>
>
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