We should add an integration test to cover async wal replication to secondary regions.
Async wal replication to region replicas has been committed (
HBASE-11568) and flush /compaction handling ( HBASE-11569) and failover handling for secondary region replicas ( HBASE-11580) is in the works.
The test can use LoadTestTool over a table with region replicas. We can write to the primary regions, and read from the secondary region replicas in reader threads to do the verification.