@Override
    protected BlockingQueue<Long> createWriteKeysQueue(Configuration conf) {
      this.delayMs = conf.getLong(String.format("%s.%s",
        IntegrationTestRegionReplicaReplication.class.getSimpleName(), OPT_READ_DELAY_MS), 5000);
      return new ConstantDelayQueue<>(TimeUnit.MILLISECONDS, delayMs);
    }
This extends MultiThreadedWriter to add a configurable delay to the keys written by the writer
threads to become available to the MultiThradedReader threads. We add this delay because of the
async nature of the wal replication to region replicas.
hbase-it/src/test/java/org/apache/hadoop/hbase/IntegrationTestRegionReplicaReplication.java