Backward / forward compatibility tests for volumedriver

[redlicha]

Purpose: detect incompatibilities between VolumeDriver versions

Test description

Cover area

• VolumeDriver operation / maintainability

User story

VolumeDriver updates (temporarily) lead to different versions running next to each other in a vpool. This means that VolumeDriver updates need to be backward compatible (~ volumes can be migrated from instances running old versions to instances running new versions) and generally also forward compatible (~ volumes can be migrated from instances running new versions to instances running old versions).

Potential problem that might occur

Expected behaviour: volume migration back and forth between different versions should work, i.e. the volumes can still be written to / read from and they respond to mgmt requests. In case of a compatibility issue, a possible symptom is that the volume migration does not succeed, i.e. the volume is stopped successfully on the old owner but it's not restarted successfully on the new owner.

Setup

General idea:

• run two VolumeDriver instances, one with an old version (stable release) and one with a new version (unstable):
• backward compatibility:
  • create a new vpool with the old version, expand it with a new version
  • create a volume on the old instance
  • start I/O
  • move volume to the new instance
  • I/O should not report errors
• forward compatibility:
  • create a new vpool with the new version, expand it with an old version
  • create a volume on the new instance
  • start I/O
  • move volume to the old instance
  • I/O should not report errors

Note: the proposed test is not exhaustive in that it cannot not expose all potential incompatibilities, but only a first line of defense. Long running tests on mixed version vpools should still also be implemented.