Snapshot Integration with GD2

[atinmu]

This github issue is going to track the overall snapshot integration related work required at GD2 workspace.

Checklist

• ReST APIs availibility in wiki
• CLI commands
• Sufficient logging
• Availibility of metrics data if applicable
• Xlator options table upto date?
• Test cases & test coverage of the functionality

[rafikc30]

Snapshot integration commands

• Snapshot-create

• Snapshot-activate

• Snapshot-deactivate

• Snapshot-list

• Snapshot-info

• Snapshot-status

• Snapshot-config

• Snapshot-clone

• Snapshot-resotre

• Snapshot-delete

First four will be targetting for mvp2

[aravindavk]

@rafikc30 please provide details about each snapshot command similar to #421 (comment)

[rafikc30]

A snapshot is always coupled with a volume, so when a volume is deleted we have to make sure that all snapshots are deleted prior to that.
To have an association we could have a list of snapshot in volinfo, but in this case any a creation or deletion of snapshot means you need to fetch the volume as well. Which can be a costly operation as we want to reduce the access to etcd.

So what I'm thinking to have a structured key in etcd store for each volume. Currently volinfos are stored as key gluster/volumes/{volname}, instead, if we could have a key like

for volinfo
gluster/volumes/{volname}/volinfo/info
for snapshot
gluster/volumes/{volname}/snapinfo/{snapname}

This is way, we can avoid updating the volinfo each time. With this method, we need to modify a little bit to get the list of volumes.

@prashanthpai @kshlm @aravindavk what is your thoughts about this ?

[atinmu]

@rafikc30 Are we blocked on the above discussions? Can we get to a consensus here asap?