Motivation:
Due to the complexity of handling deregistration and re-registration of
a channel, we previously decided to remove the deregister() operation
completely to simplify our code. However, we realized that it shouldn't
be that complicated to implement it during our discussion about making
I/O scheduling more flexible and more customizable [1], and thus the
removal of deregistration and re-registration is unnecessary now.
Modification:
- Revert commit c149f4bcc0c0d02aa1abcd5e39c155a9e598822e
- Revert commit e743a27e752f0badaf71688457793d0aa365a3ac
- Make some additional adjustments
Result:
- deregister(), fireChannelUnregistered(), and channelRegistered() were
added back..
- Channel constructors do not require an EventLoop anymore.
[1] https://github.com/netty/netty/issues/2250
- Related: #2163
- Add ResourceLeakHint to allow a user to provide a meaningful information about the leak when touching it
- DefaultChannelHandlerContext now implements ResourceLeakHint to tell where the message is going.
- Cleaner resource leak report by excluding noisy stack trace elements
- Fixes#1808
- Move all methods in ChannelInboundHandler and ChannelOutboundHandler up to ChannelHandler
- Remove ChannelInboundHandler and ChannelOutboundHandler
- Deprecate ChannelInboundHandlerAdapter, ChannelOutboundHandlerAdapter, and ChannelDuplexHandler
- Replace CombinedChannelDuplexHandler with ChannelHandlerAppender
because it's not possible to combine two handlers into one easily now
- Introduce 'Skip' annotation to pass events through efficiently
- Remove all references to the deprecated types and update Javadoc
- Fixes#1912
- Add ChannelHandlerInvoker and its default implementation
- Add pipeline manipulation methods that accept ChannelHandlerInvoker
- Rename Channel(Inbound|Outbound)Invoker to
Channel(Inbound|Outbound)Ops to avoid confusion
- Remove the Javadoc references to the package-private interfaces
Introduce a new interface called MessageSizeEstimator. This can be specific per Channel (via ChannelConfig). The MessageSizeEstimator will be used to estimate for a message that should be written. The default implementation handles ByteBuf, ByteBufHolder and FileRegion. A user is free to plug-in his/her own implementation for different behaviour.
This fixes#1664 and revert also the original commit which was meant to fix it 3b1881b523e61496d9bc50e44927f7b58fa449e6 . The problem with the original commit was that it could delay handlerRemove(..) calls and so mess up the order or forward bytes to late.
- Remove unnecessary ascending traversal of pipeline in DefaultChannelHandlerContext.freeInbound()
- Move DefaultChannelHandlerContext.teardownAll() to DefaultChannelPipeline
- Merge MessageList into ChannelOutboundBuffer
- Make ChannelOutboundBuffer a queue-like data structure so that it is nearly impossible to leak a message
- Make ChannelOutboundBuffer public so that AbstractChannel can expose it to its subclasses.
- TODO: Re-enable gathering write in NioSocketChannel
- write() now accepts a ChannelPromise and returns ChannelFuture as most
users expected. It makes the user's life much easier because it is
now much easier to get notified when a specific message has been
written.
- flush() does not create a ChannelPromise nor returns ChannelFuture.
It is now similar to what read() looks like.
DefaultChannelHandlerContext does not trigger exceptionCaught() immediately when ChannelOutboundHandler.write() raises an exception. It just records the exception until flush() is triggered. On invokeFlush(), if there's any exception recorded, DefaultChannelHandlerContext will fail the promise without calling ChannelOutboundHandler.flush(). If more than one exception were raised, only the first exception is used as the cause of the failure and the others will be logged at warn level.
- Remove channelReadSuspended because it's actually same with messageReceivedLast
- Rename messageReceived to channelRead
- Rename messageReceivedLast to channelReadComplete
We renamed messageReceivedLast to channelReadComplete because it
reflects what it really is for. Also, we renamed messageReceived to
channelRead for consistency in method names.
I must admit MesageList was pain in the ass. Instead of forcing a
handler always loop over the list of messages, this commit splits
messageReceived(ctx, list) into two event handlers:
- messageReceived(ctx, msg)
- mmessageReceivedLast(ctx)
When Netty reads one or more messages, messageReceived(ctx, msg) event
is triggered for each message. Once the current read operation is
finished, messageReceivedLast() is triggered to tell the handler that
the last messageReceived() was the last message in the current batch.
Similarly, for outbound, write(ctx, list) has been split into two:
- write(ctx, msg)
- flush(ctx, promise)
Instead of writing a list of message with a promise, a user is now
supposed to call write(msg) multiple times and then call flush() to
actually flush the buffered messages.
Please note that write() doesn't have a promise with it. You must call
flush() to get notified on completion. (or you can use writeAndFlush())
Other changes:
- Because MessageList is completely hidden, codec framework uses
List<Object> instead of MessageList as an output parameter.
This reverts commit a1a86b9de48e4696e3496904dd972336f57b4a0b because the
semantic of ctx.isRemoved() is confusing to a user - why is
ctx.isRemoved() false when handlerRemoved() is invoked? A better
solution would be check if the connection is inactive and mark the
promise as failure before attempting to write anything.
The API changes made so far turned out to increase the memory footprint
and consumption while our intention was actually decreasing them.
Memory consumption issue:
When there are many connections which does not exchange data frequently,
the old Netty 4 API spent a lot more memory than 3 because it always
allocates per-handler buffer for each connection unless otherwise
explicitly stated by a user. In a usual real world load, a client
doesn't always send requests without pausing, so the idea of having a
buffer whose life cycle if bound to the life cycle of a connection
didn't work as expected.
Memory footprint issue:
The old Netty 4 API decreased overall memory footprint by a great deal
in many cases. It was mainly because the old Netty 4 API did not
allocate a new buffer and event object for each read. Instead, it
created a new buffer for each handler in a pipeline. This works pretty
well as long as the number of handlers in a pipeline is only a few.
However, for a highly modular application with many handlers which
handles connections which lasts for relatively short period, it actually
makes the memory footprint issue much worse.
Changes:
All in all, this is about retaining all the good changes we made in 4 so
far such as better thread model and going back to the way how we dealt
with message events in 3.
To fix the memory consumption/footprint issue mentioned above, we made a
hard decision to break the backward compatibility again with the
following changes:
- Remove MessageBuf
- Merge Buf into ByteBuf
- Merge ChannelInboundByte/MessageHandler and ChannelStateHandler into ChannelInboundHandler
- Similar changes were made to the adapter classes
- Merge ChannelOutboundByte/MessageHandler and ChannelOperationHandler into ChannelOutboundHandler
- Similar changes were made to the adapter classes
- Introduce MessageList which is similar to `MessageEvent` in Netty 3
- Replace inboundBufferUpdated(ctx) with messageReceived(ctx, MessageList)
- Replace flush(ctx, promise) with write(ctx, MessageList, promise)
- Remove ByteToByteEncoder/Decoder/Codec
- Replaced by MessageToByteEncoder<ByteBuf>, ByteToMessageDecoder<ByteBuf>, and ByteMessageCodec<ByteBuf>
- Merge EmbeddedByteChannel and EmbeddedMessageChannel into EmbeddedChannel
- Add SimpleChannelInboundHandler which is sometimes more useful than
ChannelInboundHandlerAdapter
- Bring back Channel.isWritable() from Netty 3
- Add ChannelInboundHandler.channelWritabilityChanges() event
- Add RecvByteBufAllocator configuration property
- Similar to ReceiveBufferSizePredictor in Netty 3
- Some existing configuration properties such as
DatagramChannelConfig.receivePacketSize is gone now.
- Remove suspend/resumeIntermediaryDeallocation() in ByteBuf
This change would have been impossible without @normanmaurer's help. He
fixed, ported, and improved many parts of the changes.
- Fixes#1366: No elegant way to free non-in/outbound buffers held by a handler
- handlerRemoved() is now also invoked when a channel is deregistered, as well as when a handler is removed from a pipeline.
- A little bit of clean-up for readability
- Fix a bug in forwardBufferContentAndRemove() where the handler buffers are not freed (mainly because we were relying on channel.isRegistered() to determine if the handler has been removed from inside the handler.
- ChunkedWriteHandler.handlerRemoved() is unnecessary anymore because ChannelPipeline now always forwards the content of the buffer.
- Fixes#1308
freeInboundBuffer() and freeOutboundBuffer() were introduced in the early days of the new API when we did not have reference counting mechanism in the buffer. A user did not want Netty to free the handler buffers had to override these methods.
However, now that we have reference counting mechanism built into the buffer, a user who wants to retain the buffers beyond handler's life cycle can simply return the buffer whose reference count is greater than 1 in newInbound/OutboundBuffer().
- Fixes#1292
- Replace DefaultChannelPipeline.inbound/outboundShutdown flag with per-context flags
- Update the flags in free() / freeInbound() / freeOutbound() for clarity
