Unresponsive OpenSDN API due to excessive Cassandra tombstone records

During HA operations such as hard node reboot and force node shutdown, when tf-api is under load, the number of Cassandra tombstone records may exceed the limit, causing the tf-config pods to become unresponsive.

To apply the issue resolution:

Manually trigger garbage collection and compaction as follows:

  1. Reduce the garbage collection grace period:

    ALTER TABLE config_db_uuid.obj_uuid_table WITH gc_grace_seconds = 10;
    
  2. After some time (10+ seconds), run the following commands to force deletion of tombstones and compact the database:

    nodetool garbagecollect -g CELL
    nodetool compact -s
    
  3. Restore default gc_grace_seconds = 864000 to avoid potential performance issues.