[ClusterLabs] Required guidance w.r.t pacemaker

[Sridhar K]

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
<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
<https://wiki.clusterlabs.org/wiki/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.

In case of any other links w.r.t usage of bundle/examples, Please share the
same.

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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