io.netty.handler.flush

Class FlushConsolidationHandler

java.lang.Object

io.netty.channel.ChannelHandlerAdapter

io.netty.channel.ChannelInboundHandlerAdapter

io.netty.channel.ChannelDuplexHandler

io.netty.handler.flush.FlushConsolidationHandler

All Implemented Interfaces:

io.netty.channel.ChannelHandler, io.netty.channel.ChannelInboundHandler, io.netty.channel.ChannelOutboundHandler

public class FlushConsolidationHandler
extends io.netty.channel.ChannelDuplexHandler

ChannelDuplexHandler which consolidates Channel.flush() / ChannelHandlerContext.flush() operations (which also includes ChannelOutboundInvoker.writeAndFlush(Object) / ChannelOutboundInvoker.writeAndFlush(Object, ChannelPromise) and ChannelOutboundInvoker.writeAndFlush(Object) / ChannelOutboundInvoker.writeAndFlush(Object, ChannelPromise)).

Flush operations are generally speaking expensive as these may trigger a syscall on the transport level. Thus it is in most cases (where write latency can be traded with throughput) a good idea to try to minimize flush operations as much as possible.

If a read loop is currently ongoing, flush(ChannelHandlerContext) will not be passed on to the next ChannelOutboundHandler in the ChannelPipeline, as it will pick up any pending flushes when channelReadComplete(ChannelHandlerContext) is triggered. If no read loop is ongoing, the behavior depends on the consolidateWhenNoReadInProgress constructor argument:

• if false, flushes are passed on to the next handler directly;
• if true, the invocation of the next handler is submitted as a separate task on the event loop. Under high throughput, this gives the opportunity to process other flushes before the task gets executed, thus batching multiple flushes into one.

If explicitFlushAfterFlushes is reached the flush will be forwarded as well (whether while in a read loop, or while batching outside of a read loop).

If the Channel becomes non-writable it will also try to execute any pending flush operations.

The FlushConsolidationHandler should be put as first ChannelHandler in the ChannelPipeline to have the best effect.

Nested Class Summary

Nested classes/interfaces inherited from interface io.netty.channel.ChannelHandler

io.netty.channel.ChannelHandler.Sharable

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_EXPLICIT_FLUSH_AFTER_FLUSHES The default number of flushes after which a flush will be forwarded to downstream handlers (whether while in a read loop, or while batching outside of a read loop).

Constructor Summary

Constructors

Constructor and Description
FlushConsolidationHandler() Create new instance which explicit flush after 256 pending flush operations at the latest.
FlushConsolidationHandler(int explicitFlushAfterFlushes) Create new instance which doesn't consolidate flushes when no read is in progress.
FlushConsolidationHandler(int explicitFlushAfterFlushes, boolean consolidateWhenNoReadInProgress) Create new instance.

Method Summary

Modifier and Type	Method and Description
void	channelRead(io.netty.channel.ChannelHandlerContext ctx, Object msg)
void	channelReadComplete(io.netty.channel.ChannelHandlerContext ctx)
void	channelWritabilityChanged(io.netty.channel.ChannelHandlerContext ctx)
void	close(io.netty.channel.ChannelHandlerContext ctx, io.netty.channel.ChannelPromise promise)
void	disconnect(io.netty.channel.ChannelHandlerContext ctx, io.netty.channel.ChannelPromise promise)
void	exceptionCaught(io.netty.channel.ChannelHandlerContext ctx, Throwable cause)
void	flush(io.netty.channel.ChannelHandlerContext ctx)
void	handlerAdded(io.netty.channel.ChannelHandlerContext ctx)
void	handlerRemoved(io.netty.channel.ChannelHandlerContext ctx)

Methods inherited from class io.netty.channel.ChannelDuplexHandler

bind, connect, deregister, read, write

Methods inherited from class io.netty.channel.ChannelInboundHandlerAdapter

channelActive, channelInactive, channelRegistered, channelUnregistered, userEventTriggered

Methods inherited from class io.netty.channel.ChannelHandlerAdapter

ensureNotSharable, isSharable

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_EXPLICIT_FLUSH_AFTER_FLUSHES

public static final int DEFAULT_EXPLICIT_FLUSH_AFTER_FLUSHES

The default number of flushes after which a flush will be forwarded to downstream handlers (whether while in a read loop, or while batching outside of a read loop).

See Also:

Constant Field Values

Constructor Detail

FlushConsolidationHandler

public FlushConsolidationHandler()

Create new instance which explicit flush after 256 pending flush operations at the latest.

FlushConsolidationHandler

public FlushConsolidationHandler(int explicitFlushAfterFlushes)

Create new instance which doesn't consolidate flushes when no read is in progress.

Parameters:

explicitFlushAfterFlushes - the number of flushes after which an explicit flush will be done.

FlushConsolidationHandler

public FlushConsolidationHandler(int explicitFlushAfterFlushes,
                                 boolean consolidateWhenNoReadInProgress)

Create new instance.

Parameters:

explicitFlushAfterFlushes - the number of flushes after which an explicit flush will be done.

consolidateWhenNoReadInProgress - whether to consolidate flushes even when no read loop is currently ongoing.

Method Detail

handlerAdded

public void handlerAdded(io.netty.channel.ChannelHandlerContext ctx)
                  throws Exception

Specified by:

handlerAdded in interface io.netty.channel.ChannelHandler

Overrides:

handlerAdded in class io.netty.channel.ChannelHandlerAdapter

Throws:

Exception

flush

public void flush(io.netty.channel.ChannelHandlerContext ctx)
           throws Exception

Specified by:

flush in interface io.netty.channel.ChannelOutboundHandler

Overrides:

flush in class io.netty.channel.ChannelDuplexHandler

Throws:

Exception

channelReadComplete

public void channelReadComplete(io.netty.channel.ChannelHandlerContext ctx)
                         throws Exception

Specified by:

channelReadComplete in interface io.netty.channel.ChannelInboundHandler

Overrides:

channelReadComplete in class io.netty.channel.ChannelInboundHandlerAdapter

Throws:

Exception

channelRead

public void channelRead(io.netty.channel.ChannelHandlerContext ctx,
                        Object msg)
                 throws Exception

Specified by:

channelRead in interface io.netty.channel.ChannelInboundHandler

Overrides:

channelRead in class io.netty.channel.ChannelInboundHandlerAdapter

Throws:

Exception

exceptionCaught

public void exceptionCaught(io.netty.channel.ChannelHandlerContext ctx,
                            Throwable cause)
                     throws Exception

Specified by:

exceptionCaught in interface io.netty.channel.ChannelHandler

Specified by:

exceptionCaught in interface io.netty.channel.ChannelInboundHandler

Overrides:

exceptionCaught in class io.netty.channel.ChannelInboundHandlerAdapter

Throws:

Exception

disconnect

public void disconnect(io.netty.channel.ChannelHandlerContext ctx,
                       io.netty.channel.ChannelPromise promise)
                throws Exception

Specified by:

disconnect in interface io.netty.channel.ChannelOutboundHandler

Overrides:

disconnect in class io.netty.channel.ChannelDuplexHandler

Throws:

Exception

close

public void close(io.netty.channel.ChannelHandlerContext ctx,
                  io.netty.channel.ChannelPromise promise)
           throws Exception

Specified by:

close in interface io.netty.channel.ChannelOutboundHandler

Overrides:

close in class io.netty.channel.ChannelDuplexHandler

Throws:

Exception

channelWritabilityChanged

public void channelWritabilityChanged(io.netty.channel.ChannelHandlerContext ctx)
                               throws Exception

Specified by:

channelWritabilityChanged in interface io.netty.channel.ChannelInboundHandler

Overrides:

channelWritabilityChanged in class io.netty.channel.ChannelInboundHandlerAdapter

Throws:

Exception

handlerRemoved

public void handlerRemoved(io.netty.channel.ChannelHandlerContext ctx)
                    throws Exception

Specified by:

handlerRemoved in interface io.netty.channel.ChannelHandler

Overrides:

handlerRemoved in class io.netty.channel.ChannelHandlerAdapter

Throws:

Exception