alluxio.worker.grpc

Class BlockReadHandler

java.lang.Object

alluxio.worker.grpc.BlockReadHandler

All Implemented Interfaces:

io.grpc.stub.StreamObserver<ReadRequest>

@NotThreadSafe
public class BlockReadHandler
extends Object
implements io.grpc.stub.StreamObserver<ReadRequest>

This class handles BlockReadRequests. Protocol: Check GrpcDataReader for additional information. 1. Once a read request is received, the handler creates a DataReader which reads chunks of data from the block worker and pushes them to the buffer. 2. The DataReader pauses if there are too many packets in flight, and resumes if there is room available. 3. The channel is closed if there is any exception during the data read/write. Threading model: Only two threads are involved at a given point of time: gRPC event thread, data reader thread. 1. The gRPC event thread accepts the read request, handles write callbacks. If any exception occurs (e.g. failed to read from stream or respond to stream) or the read request is cancelled by the client, the gRPC event thread notifies the data reader thread. 2. The data reader thread keeps reading from the file and writes to buffer. Before reading a new data chunk, it checks whether there are notifications (e.g. cancel, error), if there is, handle them properly. See more information about the notifications in the javadoc of BlockReadRequestContext about CANCEL, EOF, and ERROR flags.

See Also:

BlockReadRequestContext

Method Summary

Modifier and Type	Method and Description
protected BlockReadRequestContext	createRequestContext(ReadRequest request)
void	onCompleted()
void	onError(Throwable cause)
void	onNext(ReadRequest request)
void	onReady() Ready to restart data reader.
boolean	tooManyPendingChunks()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

onNext

public void onNext(ReadRequest request)

Specified by:

onNext in interface io.grpc.stub.StreamObserver<ReadRequest>

tooManyPendingChunks

public boolean tooManyPendingChunks()

Returns:

true if there are too many chunks in-flight

onError

public void onError(Throwable cause)

Specified by:

onError in interface io.grpc.stub.StreamObserver<ReadRequest>

onCompleted

public void onCompleted()

Specified by:

onCompleted in interface io.grpc.stub.StreamObserver<ReadRequest>

createRequestContext

protected BlockReadRequestContext createRequestContext(ReadRequest request)

Parameters:

request - the block read request

Returns:

an instance of read request based on the request read from channel

onReady

public void onReady()

Ready to restart data reader.