[ClusterLabs] Off-line build-time cluster configuration

Craig Johnston agspoon at gmail.com
Tue Apr 14 14:46:14 EDT 2020


Sorry if this has already been covered, but a perusal of recent mail
archives didn't turn up anything for me.

We are looking for help in configuring a pacemaker/corosync cluster at the
time the Linux root file system is built, or perhaps as part of a
"pre-pivot" process in the initramfs of a live-CD environment.

We are using the RHEL versions of the cluster products.  Current production
is RHEL7 based, and we are trying to move to RHEL8.

The issues we have stem from the configuration tools' expectation that they
are operating on a live system, with all cluster nodes available on the
network.  This is obviously not the case during a "kickstart" install and
configuration process.  It's also not true in an embedded environment where
all nodes are powered simultaneously and expected to become operational
without any human intervention.

We create the cluster configuration from a "system model", that describes
the available nodes, cluster managed services, fencing agents, etc..  This
model is different for each deployment, and is used as input to create a
customized Linux distribution that is deployed to a set of physical
hardware, virtual machines, or containers.  Each node, and it's root file
system, is required to be configured and ready to go, the very first time
it is ever booted.  The on-media Linux file system is also immutable, and
thus each boot is exactly like the previous one.

Under RHEL7, we were able to use the "pcs" command to create the
corosync.conf/cib.xml files for each node.
          pcs cluster setup --local --enable --force --name mycluster node1
node2 node3
          pcs -f ${CIB} property set startup-fencing=false
          pcs -f ${CIB} resource create tftp ocf:heartbeat:Xinetd
 service=tftp  --group grp_tftp

Plus a little "awk" "sed" on the corosync.conf file, and we were able to
create a working configuration that worked out of the box. It's not pretty,
but it works in spite of the fact that we feel like we're swimming up

Under RHEL8 however, the "pcs cluster" command no longer has a "--local"
option.  We can't find any tool to replace it's functionality.  We can use
"cibadmin --empty" to create a starting cib.xml file, but there is no way
to add nodes to it (or create the corosync.conf file with nodes".

Granted, we could write our own tools to create template
corosync.conf/cib.xml files, and "pcs -f" still works.  However, that
leaves us in the unenviable position where the cluster configuration schema
could change, and our tools would not be the wiser.  We'd much prefer to
use a standard and maintained interface for configuring the cluster.

Any suggestions would be very welcome.  While we have a non-standard
use-case, we don't believe it is unrealistic given the current environment
for cloud services, and automated deployment.

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