io.netty.handler.codec.http2

Class WeightedFairQueueByteDistributor

java.lang.Object

io.netty.handler.codec.http2.WeightedFairQueueByteDistributor

All Implemented Interfaces:

StreamByteDistributor

@UnstableApi
public final class WeightedFairQueueByteDistributor
extends Object
implements StreamByteDistributor

A StreamByteDistributor that is sensitive to stream priority and uses Weighted Fair Queueing approach for distributing bytes.

Inspiration for this distributor was taken from Linux's Completely Fair Scheduler to model the distribution of bytes to simulate an "ideal multi-tasking CPU", but in this case we are simulating an "ideal multi-tasking NIC".

Each write operation will use the allocationQuantum(int) to know how many more bytes should be allocated relative to the next stream which wants to write. This is to balance fairness while also considering goodput.

Nested Class Summary

Nested classes/interfaces inherited from interface io.netty.handler.codec.http2.StreamByteDistributor

StreamByteDistributor.StreamState, StreamByteDistributor.Writer

Constructor Summary

Constructors

Constructor and Description
WeightedFairQueueByteDistributor(Http2Connection connection)
WeightedFairQueueByteDistributor(Http2Connection connection, int maxStateOnlySize)

Method Summary

Modifier and Type	Method and Description
void	allocationQuantum(int allocationQuantum) Sets the amount of bytes that will be allocated to each stream.
boolean	distribute(int maxBytes, StreamByteDistributor.Writer writer) Distributes up to maxBytes to those streams containing streamable bytes and iterates across those streams to write the appropriate bytes.
void	updateDependencyTree(int childStreamId, int parentStreamId, short weight, boolean exclusive) Explicitly update the dependency tree.
void	updateStreamableBytes(StreamByteDistributor.StreamState state) Called when the streamable bytes for a stream has changed.

Methods inherited from class java.lang.Object

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

Constructor Detail

WeightedFairQueueByteDistributor

public WeightedFairQueueByteDistributor(Http2Connection connection)

WeightedFairQueueByteDistributor

public WeightedFairQueueByteDistributor(Http2Connection connection,
                                        int maxStateOnlySize)

Method Detail

updateStreamableBytes

public void updateStreamableBytes(StreamByteDistributor.StreamState state)

Description copied from interface: StreamByteDistributor

Called when the streamable bytes for a stream has changed. Until this method is called for the first time for a give stream, the stream is assumed to have no streamable bytes.

Specified by:

updateStreamableBytes in interface StreamByteDistributor

updateDependencyTree

public void updateDependencyTree(int childStreamId,
                                 int parentStreamId,
                                 short weight,
                                 boolean exclusive)

Description copied from interface: StreamByteDistributor

Explicitly update the dependency tree. This method is called independently of stream state changes.

Specified by:

updateDependencyTree in interface StreamByteDistributor

Parameters:

childStreamId - The stream identifier associated with the child stream.

parentStreamId - The stream identifier associated with the parent stream. May be 0, to make childStreamId and immediate child of the connection.

weight - The weight which is used relative to other child streams for parentStreamId. This value must be between 1 and 256 (inclusive).

exclusive - If childStreamId should be the exclusive dependency of parentStreamId.

distribute

public boolean distribute(int maxBytes,
                          StreamByteDistributor.Writer writer)
                   throws Http2Exception

Description copied from interface: StreamByteDistributor

Distributes up to maxBytes to those streams containing streamable bytes and iterates across those streams to write the appropriate bytes. Criteria for traversing streams is undefined and it is up to the implementation to determine when to stop at a given stream.

The streamable bytes are not automatically updated by calling this method. It is up to the caller to indicate the number of bytes streamable after the write by calling StreamByteDistributor.updateStreamableBytes(StreamState).

Specified by:

distribute in interface StreamByteDistributor

Parameters:

maxBytes - the maximum number of bytes to write.

Returns:

true if there are still streamable bytes that have not yet been written, otherwise false.

Throws:

Http2Exception - If an internal exception occurs and internal connection state would otherwise be corrupted.

allocationQuantum

public void allocationQuantum(int allocationQuantum)

Sets the amount of bytes that will be allocated to each stream. Defaults to 1KiB.

Parameters:

allocationQuantum - the amount of bytes that will be allocated to each stream. Must be > 0.