spark 2.1 BlockManagerId

When block manager is created, it will generate a id without topology information.
and register itself with the block manager master.
the block manager master will return a id, and it will use this id if the id is not null.

val id =      BlockManagerId(executorId, blockTransferService.hostName, blockTransferService.port, None)    val idFromMaster = master.registerBlockManager(      id,      maxMemory,      slaveEndpoint)    blockManagerId = if (idFromMaster != null) idFromMaster else id

BlockManagerMasterEndpoint.register method

private def register(      idWithoutTopologyInfo: BlockManagerId,      maxMemSize: Long,      slaveEndpoint: RpcEndpointRef): BlockManagerId = {    // the dummy id is not expected to contain the topology information.    // we get that info here and respond back with a more fleshed out block manager id    val id = BlockManagerId(      idWithoutTopologyInfo.executorId,      idWithoutTopologyInfo.host,      idWithoutTopologyInfo.port,      topologyMapper.getTopologyForHost(idWithoutTopologyInfo.host))    val time = System.currentTimeMillis()    if (!blockManagerInfo.contains(id)) {      blockManagerIdByExecutor.get(id.executorId) match {        case Some(oldId) =>          // A block manager of the same executor already exists, so remove it (assumed dead)          logError("Got two different block manager registrations on same executor - "              + s" will replace old one $oldId with new one $id")          removeExecutor(id.executorId)        case None =>      }      logInfo("Registering block manager %s with %s RAM, %s".format(        id.hostPort, Utils.bytesToString(maxMemSize), id))      blockManagerIdByExecutor(id.executorId) = id      blockManagerInfo(id) = new BlockManagerInfo(        id, System.currentTimeMillis(), maxMemSize, slaveEndpoint)    }    listenerBus.post(SparkListenerBlockManagerAdded(time, id, maxMemSize))    id  }