NettyBlockRpcServer — NettyBlockTransferService’s RpcHandler-spark技术分享

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

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

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

receive(

client: TransportClient,

rpcMessage: ByteBuffer,

responseContext: RpcResponseCallback): Unit

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

receive…FIXME

NettyBlockRpcServer — NettyBlockTransferService’s RpcHandler