spark-NettyBlockRpcServer.adoc

NettyBlockRpcServer — NettyBlockTransferService’s RpcHandler

NettyBlockRpcServer is a RpcHandler that handles messages for NettyBlockTransferService.

NettyBlockRpcServer is created when…​FIXME

NettyBlockRpcServer uses a OneForOneStreamManager for…​FIXME

Table 1. NettyBlockRpcServer Messages

Message	Behaviour
OpenBlocks	Obtaining local blocks and registering them with the internal OneForOneStreamManager
UploadBlock	Deserializes a block and stores it in BlockDataManager

Tip	Enable TRACE logging level to see received messages in the logs.

Tip	Enable TRACE logging level for org.apache.spark.network.netty.NettyBlockRpcServer logger to see what happens inside. Add the following line to conf/log4j.properties: log4j.logger.org.apache.spark.network.netty.NettyBlockRpcServer=TRACE Refer to Logging.

Obtaining Local Blocks and Registering with Internal OneForOneStreamManager — OpenBlocks Message Handler

When OpenBlocks arrives, NettyBlockRpcServer requests block data (from BlockDataManager) for every block id in the message. The block data is a collection of ManagedBuffer for every block id in the incoming message.

Note	BlockDataManager is given when NettyBlockRpcServer is created.

NettyBlockRpcServer then registers a stream of ManagedBuffers (for the blocks) with the internal StreamManager under streamId.

Note	The internal StreamManager is OneForOneStreamManager and is created when NettyBlockRpcServer is created.

You should see the following TRACE message in the logs:

TRACE NettyBlockRpcServer: Registered streamId [streamId]  with [size] buffers

In the end, NettyBlockRpcServer responds with a StreamHandle (with the streamId and the number of blocks). The response is serialized as a ByteBuffer.

Deserializing Block and Storing in BlockDataManager — UploadBlock Message Handler

When UploadBlock arrives, NettyBlockRpcServer deserializes the metadata of the input message to get the StorageLevel and ClassTag of the block being uploaded.

Note	metadata is serialized before NettyBlockTransferService sends a UploadBlock message (using the internal JavaSerializer) that is given as serializer when NettyBlockRpcServer is created.

NettyBlockRpcServer creates a BlockId for the block id and requests the BlockDataManager to store the block.

Note	The BlockDataManager is passed in when NettyBlockRpcServer is created.

In the end, NettyBlockRpcServer responds with a 0-capacity ByteBuffer.

Note	UploadBlock is sent when NettyBlockTransferService uploads a block.

Creating NettyBlockRpcServer Instance

NettyBlockRpcServer takes the following when created:

• Application ID

• Serializer

• BlockDataManager

NettyBlockRpcServer initializes the internal registries and counters.

Receiving RPC Messages — receive Method

receive(
  client: TransportClient,
  rpcMessage: ByteBuffer,
  responseContext: RpcResponseCallback): Unit

Note	receive is part of RpcHandler Contract to…​FIXME.

receive…​FIXME