Currently, Sentry does not start HMSFollower when HDFS sync is disabled. This breaks PERM sync. For example, when a table/database is dropped, its permission should be removed when perm sync is enabled. Without HMSFollower, Sentry does not know when table/database is dropped, and therefore, cannot remove the permission accordingly.
Sentry needs to make updates to have the follow behavior
1) When HDFS sync is disabled + PERM sync is disabled, do not start HMSFollower
2) when HDFS sync is enabled or PERM sync is enabled, start HMSFollower (Sentry change).
3) when HDFS sync is enabled, we save path change and perm change. nothing more.
4) when perm sync is enabled, we update perm when table/database is created, dropped or altered, nothing more.