@Override
  public void unblockStateTransition() {
      this.blockStateTransitionLatch.countDown();
  }
With auto-registration instanceConfig is populated on participant registration, also triggering state transition
We have a latch that blocks state transition until this method is called, which is called after listeners of
StorageManager, StatsManager, and ReplicationManager is registered
ambry-clustermap/src/main/java/com/github/ambry/clustermap/HelixParticipant.java