[ovs-discuss] Questions: OVS-DB running raft mode

[Alexander Constantinescu]

Hi

My name is Alexander Constantinescu. I am working for Red Hat on
implementing OVN in a cloud environment (effectively working on
ovn-org/ovn-kubernetes) with an OVS database running in clustered mode.

We have a couple of questions concerning the expected behaviour of the DB
raft cluster w.r.t the amount of members during creation/runtime.

Background: the DB cluster will be deployed across X master nodes - which
is user defined (i.e the user can specify how much X is). Raft
consensus requires at least (n/2)+1 nodes.

   - What is expected from the OVS DB if a user decides to create only 1
   master node, for example? We are noticing that it deploys just fine
   (without any indication of issues in the logs), but is it *really *fine?
   Is it even running in cluster mode? Can we expect transactions to the DB to
   work fine? According to the consensus formula above it would just mean that
   the cluster cannot lose any member, but I would just like to confirm that
   my understanding is correct and aligned with the implementation.
   - What is the expected behaviour if a raft cluster is created with an
   amount of master nodes satisfying the requirement of raft consensus, but
   some nodes disappear during its lifecycle and this condition ceases to
   hold? We have noticed that the northbound/southbound databases ports close,
   is this a correct deduction according to the clustered implementation?

Thanks in advance for any answer(s)!

Best regards,


Alexander Constantinescu

Software Engineer, Openshift SDN

Red Hat <https://www.redhat.com/>

aconstan at redhat.com
<https://www.redhat.com/>
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