Support to get maximum op-version supported in a heterogeneous cluster

[samikshan]

gluster volume get <volname> cluster.op-version can provide the current op-version the cluster is running with. However there is no way for users to know the maximum value to which they can bump up the op-version. Given that auto op-version update doesn't happen on an upgrade, users might end up running the cluster with an older op-version. The focus area covered by this feature is 'user experience'

Related bug in bugzilla: #1365822

[joejulian]

Would be helpful if this could also return the max op-version for each connected client as well, along with the client address. Perhaps a two-form version of this command:

gluster volume get all cluster.max-op-version 

which would simply return a single entry with the max supported op-version, and

gluster volume get all cluster.max-op-version detail

Which would show the max op-version for each server and (known) client.

This would aid quite a few users that have asked how to track down which client doesn't support the op-version necessary for any given command.

[atinmu]

I think the right place holder for this would be gluster volume status client and BZ 1302944 is what this RFE tracks with.

[joejulian]

If we're building a way to get the max op-version, the client op-version is every bit as important. When a configuration management tool queries so it can automatically set the op-version, it's best if it's all in one place.

[atinmu]

If we'd have to do that, then we shouldn't use the cluster name space here as that indicates the op-version (glusterd) of the cluster.

[samikshan]

The purpose that is served from getting the maximum supported op-version in a running cluster is to let the admin/user know the maximum op-version to which the cluster can be bumped up to so that new features can be accessed. Since this op-version bump up wouldn't really affect the clients, I believe it would be better to keep the max-op-version data for clients out of this particular feature.

Having said that, the max-op-version data for clients can be added to the volume status <VOLNAME|all> clients command output that currently provides us with the following information on clients:

1. Brick name
2. Client count for each brick
3. hostname:port for each client
4. Bytes read and written for each client

http://review.gluster.org/#/c/16303/ aims to exactly do this by adding the maximum supported op-version in each client to the above list of data points.

[atinmu]

The patch is now into mainline.

[ShyamsundarR]

Part of release-3.10 as well.