Hi! I'm working on adding HBase 3 support for Phoenix.
RegionObserver#preWalRestore has been removed in HBASE-28480 <https://issues.apache.org/jira/browse/HBASE-28480> This feature is use by the Phoenix indexing code, and is also needed by the in development Phoenix High Availability Consistent failover feature PHOENIX-7562 <https://issues.apache.org/jira/browse/PHOENIX-7562> . Phoenix does have a replacement for the old indexing code, so breaking that is not necessarily a critical issue, however the upcoming Phoenix HA Rearchitecture for Consistent Failover feature also depends on the existence of this hook.
