private SyncReplicationState getSyncReplicationState(String peerId, String path)
    throws ReplicationException {
    try {
      byte[] data = ZKUtil.getData(zookeeper, path);
      if (data == null || data.length == 0) {
        if (ZKUtil.checkExists(zookeeper, getPeerNode(peerId)) != -1) {
          // should be a peer from previous version, set the sync replication state for it.
          ZKUtil.createSetData(zookeeper, path, NONE_STATE_ZNODE_BYTES);
          return SyncReplicationState.NONE;
        } else {
          throw new ReplicationException(
            "Replication peer sync state shouldn't be empty, peerId=" + peerId);
        }
      }
      return SyncReplicationState.parseFrom(data);
    } catch (KeeperException | InterruptedException | IOException e) {
      throw new ReplicationException(
        "Error getting sync replication state of path " + path + " for peer with id=" + peerId, e);
    }
  }
The name of the znode that contains a list of all remote slave (i.e. peer) clusters.
hbase-replication/src/main/java/org/apache/hadoop/hbase/replication/ZKReplicationPeerStorage.java