Add support for rolling back snapshots

We supported creating snapshots, but not doing anything with them. This
removes the manual task of restoring a snapshot and replace it with a
PVC abstraction of rolling back to a snapshot.

While Ceph recommends cloning a snapshot instead of rolling back, due to
the time taken, in our usecase I don't think that is an optimal
strategy, as it will leave dangling clones that we'd then have to
manage.

Closes #183

client-cli/pvc/cli/cli.py

@@ -4372,6 +4372,32 @@ def cli_storage_volume_snapshot_remove(pool, volume, name):
     finish(retcode, retmsg)
 
 
+###############################################################################
+# > pvc storage volume snapshot rollback
+###############################################################################
+@click.command(name="rollback", short_help="Roll back RBD volume to snapshot.")
+@connection_req
+@click.argument("pool")
+@click.argument("volume")
+@click.argument("name")
+@confirm_opt("Roll back to snapshot {name} for volume {pool}/{volume}")
+def cli_storage_volume_snapshot_rollback(pool, volume, name):
+    """
+    Roll back the Ceph RBD volume VOLUME in pool POOL to the snapshot NAME.
+
+    DANGER: All data written to the volume since the given snapshot will be permanently lost.
+
+    WARNING: A rollback cannot be performed on an RBD volume with active I/O. Doing so will cause
+    undefined behaviour and possible corruption. Ensure that any VM(s) using this RBD volume are
+    stopped or disabled before attempting a snapshot rollback.
+    """
+
+    retcode, retmsg = pvc.lib.storage.ceph_snapshot_rollback(
+        CLI_CONFIG, pool, volume, name
+    )
+    finish(retcode, retmsg)
+
+
 ###############################################################################
 # > pvc storage volume snapshot list
 ###############################################################################
@@ -6349,6 +6375,7 @@ cli_storage_volume.add_command(cli_storage_volume_list)
 cli_storage_volume_snapshot.add_command(cli_storage_volume_snapshot_add)
 cli_storage_volume_snapshot.add_command(cli_storage_volume_snapshot_rename)
 cli_storage_volume_snapshot.add_command(cli_storage_volume_snapshot_remove)
+cli_storage_volume_snapshot.add_command(cli_storage_volume_snapshot_rollback)
 cli_storage_volume_snapshot.add_command(cli_storage_volume_snapshot_list)
 cli_storage_volume.add_command(cli_storage_volume_snapshot)
 cli_storage.add_command(cli_storage_volume)

client-cli/pvc/lib/storage.py

@@ -1544,6 +1544,30 @@ def ceph_snapshot_add(config, pool, volume, snapshot):
     return retstatus, response.json().get("message", "")
 
 
+def ceph_snapshot_rollback(config, pool, volume, snapshot):
+    """
+    Roll back Ceph volume to snapshot
+
+    API endpoint: POST /api/v1/storage/ceph/snapshot/{pool}/{volume}/{snapshot}/rollback
+    API arguments:
+    API schema: {"message":"{data}"}
+    """
+    response = call_api(
+        config,
+        "post",
+        "/storage/ceph/snapshot/{pool}/{volume}/{snapshot}/rollback".format(
+            snapshot=snapshot, volume=volume, pool=pool
+        ),
+    )
+
+    if response.status_code == 200:
+        retstatus = True
+    else:
+        retstatus = False
+
+    return retstatus, response.json().get("message", "")
+
+
 def ceph_snapshot_remove(config, pool, volume, snapshot):
     """
     Remove Ceph snapshot