public class FlowControlHandler extends ChannelDuplexHandler
FlowControlHandler ensures that only one message per read() is sent downstream.
Classes such as ByteToMessageDecoder or MessageToByteEncoder are free to emit as
many events as they like for any given input. A channel's auto reading configuration doesn't usually
apply in these scenarios. This is causing problems in downstream ChannelHandlers that would
like to hold subsequent events while they're processing one event. It's a common problem with the
HttpObjectDecoder that will very often fire a HttpRequest that is immediately followed
by a LastHttpContent event.
{@code
ChannelPipeline pipeline = ...;
pipeline.addLast(new HttpServerCodec());
pipeline.addLast(new FlowControlHandler());
pipeline.addLast(new MyExampleHandler());
class MyExampleHandler extends ChannelInboundHandlerAdapter {ChannelConfig.setAutoRead(boolean)| Modifier and Type | Class and Description |
|---|---|
private static class |
FlowControlHandler.RecyclableArrayDeque
A recyclable
ArrayDeque. |
ChannelHandler.Sharable| Modifier and Type | Field and Description |
|---|---|
private ChannelConfig |
config |
private static InternalLogger |
logger |
private FlowControlHandler.RecyclableArrayDeque |
queue |
private boolean |
releaseMessages |
private boolean |
shouldConsume |
| Constructor and Description |
|---|
FlowControlHandler() |
FlowControlHandler(boolean releaseMessages) |
| Modifier and Type | Method and Description |
|---|---|
void |
channelInactive(ChannelHandlerContext ctx)
Calls
ChannelHandlerContext.fireChannelInactive() to forward
to the next ChannelInboundHandler in the ChannelPipeline. |
void |
channelRead(ChannelHandlerContext ctx,
java.lang.Object msg)
Calls
ChannelHandlerContext.fireChannelRead(Object) to forward
to the next ChannelInboundHandler in the ChannelPipeline. |
void |
channelReadComplete(ChannelHandlerContext ctx)
Calls
ChannelHandlerContext.fireChannelReadComplete() to forward
to the next ChannelInboundHandler in the ChannelPipeline. |
private int |
dequeue(ChannelHandlerContext ctx,
int minConsume)
Dequeues one or many (or none) messages depending on the channel's auto
reading state and returns the number of messages that were consumed from
the internal queue.
|
private void |
destroy()
Releases all messages and destroys the
Queue. |
void |
handlerAdded(ChannelHandlerContext ctx)
Do nothing by default, sub-classes may override this method.
|
(package private) boolean |
isQueueEmpty()
Determine if the underlying
Queue is empty. |
void |
read(ChannelHandlerContext ctx)
Calls
ChannelHandlerContext.read() to forward
to the next ChannelOutboundHandler in the ChannelPipeline. |
bind, close, connect, deregister, disconnect, flush, writechannelActive, channelRegistered, channelUnregistered, channelWritabilityChanged, exceptionCaught, userEventTriggeredensureNotSharable, handlerRemoved, isSharableclone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, waitexceptionCaught, handlerRemovedprivate static final InternalLogger logger
private final boolean releaseMessages
private FlowControlHandler.RecyclableArrayDeque queue
private ChannelConfig config
private boolean shouldConsume
public FlowControlHandler()
public FlowControlHandler(boolean releaseMessages)
boolean isQueueEmpty()
Queue is empty. This method exists for
testing, debugging and inspection purposes and it is not Thread safe!private void destroy()
Queue.public void handlerAdded(ChannelHandlerContext ctx) throws java.lang.Exception
ChannelHandlerAdapterhandlerAdded in interface ChannelHandlerhandlerAdded in class ChannelHandlerAdapterjava.lang.Exceptionpublic void channelInactive(ChannelHandlerContext ctx) throws java.lang.Exception
ChannelInboundHandlerAdapterChannelHandlerContext.fireChannelInactive() to forward
to the next ChannelInboundHandler in the ChannelPipeline.
Sub-classes may override this method to change behavior.channelInactive in interface ChannelInboundHandlerchannelInactive in class ChannelInboundHandlerAdapterjava.lang.Exceptionpublic void read(ChannelHandlerContext ctx) throws java.lang.Exception
ChannelDuplexHandlerChannelHandlerContext.read() to forward
to the next ChannelOutboundHandler in the ChannelPipeline.
Sub-classes may override this method to change behavior.read in interface ChannelOutboundHandlerread in class ChannelDuplexHandlerjava.lang.Exceptionpublic void channelRead(ChannelHandlerContext ctx, java.lang.Object msg) throws java.lang.Exception
ChannelInboundHandlerAdapterChannelHandlerContext.fireChannelRead(Object) to forward
to the next ChannelInboundHandler in the ChannelPipeline.
Sub-classes may override this method to change behavior.channelRead in interface ChannelInboundHandlerchannelRead in class ChannelInboundHandlerAdapterjava.lang.Exceptionpublic void channelReadComplete(ChannelHandlerContext ctx) throws java.lang.Exception
ChannelInboundHandlerAdapterChannelHandlerContext.fireChannelReadComplete() to forward
to the next ChannelInboundHandler in the ChannelPipeline.
Sub-classes may override this method to change behavior.channelReadComplete in interface ChannelInboundHandlerchannelReadComplete in class ChannelInboundHandlerAdapterjava.lang.Exceptionprivate int dequeue(ChannelHandlerContext ctx, int minConsume)
minConsume argument is used to force dequeue() into
consuming that number of messages regardless of the channel's auto
reading configuration.