Ceph » rbd

If the 'rbd-mirror' daemon is falling behind, it can fail to unlink itself from any intermediate snapshots that it decides to skip over:

2020-12-09T21:40:43.798-0500 7f1359597700 10 rbd::mirror::image_replayer::snapshot::Replayer: 0x5651c7f0d800 scan_remote_mirror_snapshots: 
2020-12-09T21:40:43.798-0500 7f1359597700 15 rbd::mirror::image_replayer::snapshot::Replayer: 0x5651c7f0d800 scan_remote_mirror_snapshots: remote mirror snapshot: id=2397, mirror_ns=[mirror state=primary, complete=1, mirror_peer_uuids=94b2df87-aec9-4bba-b7e9-2561c537ab0c, primary_mirror_uuid=, primary_snap_id=head, last_copied_object_number=0, snap_seqs={}]
2020-12-09T21:40:43.798-0500 7f1359597700 15 rbd::mirror::image_replayer::snapshot::Replayer: 0x5651c7f0d800 scan_remote_mirror_snapshots: skipping synced remote snapshot 2397
2020-12-09T21:40:43.798-0500 7f1359597700 15 rbd::mirror::image_replayer::snapshot::Replayer: 0x5651c7f0d800 scan_remote_mirror_snapshots: remote mirror snapshot: id=5175, mirror_ns=[mirror state=primary, complete=1, mirror_peer_uuids=94b2df87-aec9-4bba-b7e9-2561c537ab0c, primary_mirror_uuid=, primary_snap_id=head, last_copied_object_number=0, snap_seqs={}]
2020-12-09T21:40:43.798-0500 7f1359597700 15 rbd::mirror::image_replayer::snapshot::Replayer: 0x5651c7f0d800 scan_remote_mirror_snapshots: remote mirror snapshot: id=5176, mirror_ns=[mirror state=primary, complete=1, mirror_peer_uuids=94b2df87-aec9-4bba-b7e9-2561c537ab0c, primary_mirror_uuid=, primary_snap_id=head, last_copied_object_number=0, snap_seqs={}]
2020-12-09T21:40:43.798-0500 7f1359597700 10 rbd::mirror::image_replayer::snapshot::Replayer: 0x5651c7f0d800 scan_remote_mirror_snapshots: unlinking from remote snapshot 5176
2020-12-09T21:40:43.798-0500 7f1359597700 10 rbd::mirror::image_replayer::snapshot::Replayer: 0x5651c7f0d800 unlink_peer: remote_snap_id=5176
2020-12-09T21:40:43.849-0500 7f1352d8a700 10 rbd::mirror::image_replayer::snapshot::Replayer: 0x5651c7f0d800 handle_unlink_peer: r=0

This results in the most up-to-date snapshot getting unlinked improperly which leaves a mirrored snapshot with an empty set of peers. This results in several other bugs.