Motivation:
At the moment it is possible to see a NPE when the LocalSocketChannels doRegister() method is called and the LocalSocketChannels doClose() method is called before the registration was completed.
Modifications:
Make sure we delay the actual close until the registration task was executed.
Result:
No more NPE
Motivation:
At the moment an IllegalArgumentException will be thrown if a ChannelPromise is cancelled while propagate through the ChannelPipeline. This is not correct, we should just stop to propagate it as it is valid to cancel at any time.
Modifications:
Stop propagate the operation through the ChannelPipeline once a ChannelPromise is cancelled.
Result:
No more IllegalArgumentException when cancel a ChannelPromise while moving through the ChannelPipeline.
- Fixes#2060
- Ensure to return a future/promise implementation that does not fail with 'not registered to an event loop' error for registration operations
- If there is no usable event loop available, GlobalEventExecutor.INSTANCE is used as a fallback.
- 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.
- 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.
- SimpleChannelInboundHandler now has a constructor parameter to let a
user decide to enable automatic message release. (the default is to
enable), which makes ChannelInboundConsumingHandler of less value.
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.
- Use the local transport in a correct way (i.e. no need to trigger channelActive et al by ourselves)
- Use Promise/Future instead of CountDownLatch where they simplifies
shutdownGracefully() provides two optional parameters that give more
control over when an executor has to be shut down.
- Related issue: #1307
- Add shutdownGracefully(..) and isShuttingDown()
- Deprecate shutdown() / shutdownNow()
- Replace lastAccessTime with lastExecutionTime and update it after task
execution for accurate quiet period check
- runAllTasks() and runShutdownTasks() update it automatically.
- Add updateLastExecutionTime() so that subclasses can update it
- Add a constructor parameter that tells not to add an unncessary wakeup
task in execute() if addTask() wakes up the executor thread
automatically. Previously, execute() always called wakeup() after
addTask(), which often caused an extra dummy task in the task queue.
- Use shutdownGracefully() wherever possible / Deprecation javadoc
- Reduce the running time of SingleThreadEventLoopTest from 40s to 15s
using custom graceful shutdown parameters
- Other changes made along with this commit:
- takeTask() does not throw InterruptedException anymore.
- Returns null on interruption or wakeup
- Make sure runShutdownTasks() return true even if an exception was
raised while running the shutdown tasks
- Remove unnecessary isShutdown() checks
- Consistent use of SingleThreadEventExecutor.nanoTime()
Replace isWakeupOverridden with a constructor parameter
- 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().
This change also introduce a few other changes which was needed:
* ChannelHandler.beforeAdd(...) and ChannelHandler.beforeRemove(...) were removed
* ChannelHandler.afterAdd(...) -> handlerAdded(...)
* ChannelHandler.afterRemoved(...) -> handlerRemoved(...)
* SslHandler.handshake() -> SslHandler.hanshakeFuture() as the handshake is triggered automatically after
the Channel becomes active
This commit splits bridge into two parts. One is NextBridgeFeeder,
which provides ByteBuf and MessageBuf that are local to the context
whose next*Buffer() has been invoked on. The other is a thread-safe
queue that stores the data fed by NextBridgeFeeder.feed().
By splitting the bridge into the two parts, the data pushed by a handler
is not lost anymore when the next handler who provided the next buffer
is removed from the pipeline.
- Fixes#1272
- Count the number of select() calls made to wait until reaching at the expected dead line, and rebuild selectors if too many select() calls were made.
- Similar to @normanmaurer's fix in that this commit also makes Bootstrap.init(Channel) asynchronous, but it is simpler and less invasive.
- Also made sure a connection attempt failure in the local transport does not trigger an exceptionCaught event
- The offending test case is annotated with `@Ignore`
- Also fixed a bug where channel initialization failure swallows the original cause of initialization failure
- Add ChannelHandlerUtil and move the core logic of ChannelInbound/OutboundMessageHandler to ChannelHandlerUtil
- Add ChannelHandlerUtil.SingleInbound/OutboundMessageHandler and make ChannelInbound/OutboundMessageHandlerAdapter implement them. This is a backward incompatible change because it forces all handler methods to be public (was protected previously)
- Fixes: #1119
- Rename ChannelHandlerAdapter to ChannelDuplexHandler
- Add ChannelHandlerAdapter that implements only ChannelHandler
- Rename CombinedChannelHandler to CombinedChannelDuplexHandler and
improve runtime validation
- Remove ChannelInbound/OutboundHandlerAdapter which are not useful
- Make ChannelOutboundByteHandlerAdapter similar to
ChannelInboundByteHandlerAdapter
- Make the tail and head handler of DefaultChannelPipeline accept both
bytes and messages. ChannelHandlerContext.hasNext*() were removed
because they always return true now.
- Removed various unnecessary null checks.
- Correct method/field names:
inboundBufferSuspended -> channelReadSuspended
This pull request adds two new handler methods: discardInboundReadBytes(ctx) and discardOutboundReadBytes(ctx) to ChannelInboundByteHandler and ChannelOutboundByteHandler respectively. They are called between every inboundBufferUpdated() and flush() respectively. Their default implementation is to call discardSomeReadBytes() on their buffers and a user can override this behavior easily. For example, ReplayingDecoder.discardInboundReadBytes() looks like the following:
@Override
public void discardInboundReadBytes(ChannelHandlerContext ctx) throws Exception {
ByteBuf in = ctx.inboundByteBuffer();
final int oldReaderIndex = in.readerIndex();
super.discardInboundReadBytes(ctx);
final int newReaderIndex = in.readerIndex();
checkpoint -= oldReaderIndex - newReaderIndex;
}
If a handler, which has its own buffer index variable, extends ReplayingDecoder or ByteToMessageDecoder, the handler can also override discardInboundReadBytes() and adjust its index variable accordingly.
This pull request introduces a new operation called read() that replaces the existing inbound traffic control method. EventLoop now performs socket reads only when the read() operation has been issued. Once the requested read() operation is actually performed, EventLoop triggers an inboundBufferSuspended event that tells the handlers that the requested read() operation has been performed and the inbound traffic has been suspended again. A handler can decide to continue reading or not.
Unlike other outbound operations, read() does not use ChannelFuture at all to avoid GC cost. If there's a good reason to create a new future per read at the GC cost, I'll change this.
This pull request consequently removes the readable property in ChannelHandlerContext, which means how the traffic control works changed significantly.
This pull request also adds a new configuration property ChannelOption.AUTO_READ whose default value is true. If true, Netty will call ctx.read() for you. If you need a close control over when read() is called, you can set it to false.
Another interesting fact is that non-terminal handlers do not really need to call read() at all. Only the last inbound handler will have to call it, and that's just enough. Actually, you don't even need to call it at the last handler in most cases because of the ChannelOption.AUTO_READ mentioned above.
There's no serious backward compatibility issue. If the compiler complains your handler does not implement the read() method, add the following:
public void read(ChannelHandlerContext ctx) throws Exception {
ctx.read();
}
Note that this pull request certainly makes bounded inbound buffer support very easy, but itself does not add the bounded inbound buffer support.
- Fixes#826
Unsafe.isFreed(), free(), suspend/resumeIntermediaryAllocations() are not that dangerous. internalNioBuffer() and internalNioBuffers() are dangerous but it seems like nobody is using it even inside Netty. Removing those two methods also removes the necessity to keep Unsafe interface at all.
This pull request introduces the new default ByteBufAllocator implementation based on jemalloc, with a some differences:
* Minimum possible buffer capacity is 16 (jemalloc: 2)
* Uses binary heap with random branching (jemalloc: red-black tree)
* No thread-local cache yet (jemalloc has thread-local cache)
* Default page size is 8 KiB (jemalloc: 4 KiB)
* Default chunk size is 16 MiB (jemalloc: 2 MiB)
* Cannot allocate a buffer bigger than the chunk size (jemalloc: possible) because we don't have control over memory layout in Java. A user can work around this issue by creating a composite buffer, but it's not always a feasible option. Although 16 MiB is a pretty big default, a user's handler might need to deal with the bounded buffers when the user wants to deal with a large message.
Also, to ensure the new allocator performs good enough, I wrote a microbenchmark for it and made it a dedicated Maven module. It uses Google's Caliper framework to run and publish the test result (example)
Miscellaneous changes:
* Made some ByteBuf implementations public so that those who implements a new allocator can make use of them.
* Added ByteBufAllocator.compositeBuffer() and its variants.
* ByteBufAllocator.ioBuffer() creates a buffer with 0 capacity.
testConcurrentMessageBufferAccess() assumes the outbound/inbound byte buffers are unbounded. Because PooledByteBuf is bounded, the test did not pass.
The fix makes an assumption that ctx.flush() or fireInboundBufferUpdated() will make the next buffer consumed immediately, which is not the case in the real world. Under network congestion, a user will see IndexOutOfBoundsException if the user's handler implementation writes boundlessly into inbound/outbound buffers.
* UnsafeByteBuf is gone. I added ByteBuf.unsafe() back.
* To avoid extra instantiation, all ByteBuf implementations implement the ByteBuf.Unsafe interface.
* To hide this implementation detail, all ByteBuf implementations are package-private.
* AbstractByteBuf and SwappedByteBuf are public and they do not implement ByteBuf.Unsafe because they don't need to.
* unwrap() is not an unsafe operation anymore.
* ChannelBuf also has unsafe() and Unsafe. ByteBuf.Unsafe extends ChannelBuf.unsafe(). ChannelBuf.unsafe() provides free() operation so that a user does not need to down-cast the buffer in freeInbound/OutboundBuffer().
When a Netty application shuts down, a user often sees a REE
(RejectedExecutionException).
A REE is raised due to various reasons we don't have control over, such
as:
- A client connects to a server while the server is shutting down.
- An event is triggered for a closed Channel while its event loop is
also shutting down. Some of them are:
- channelDeregistered (triggered after a channel is closed)
- freeIn/OutboundBuffer (triggered after channelDeregistered)
- userEventTriggered (triggered anytime)
To address this issue, a new method called confirmShutdown() has been
added to SingleThreadEventExecutor. After a user calls shutdown(),
confirmShutdown() runs any remaining tasks in the task queue and ensures
no events are triggered for last 2 seconds. If any task are added to
the task queue before 2 seconds passes, confirmShutdown() prevents the
event loop from terminating by returning false.
Now that SingleThreadEventExecutor needs to accept tasks even after
shutdown(), its execute() method only rejects the task after the event
loop is terminated (i.e. isTerminated() returns true.) Except that,
there's no change in semantics.
SingleThreadEventExecutor also checks if its subclass called
confirmShutdown() in its run() implementation, so that Netty developers
can make sure they shut down their event loop impementation correctly.
It also fixes a bug in AioSocketChannel, revealed by delayed shutdown,
where an inboundBufferUpdated() event is triggered on a closed Channel
with deallocated buffers.
Caveats:
Because SingleThreadEventExecutor.takeTask() does not have a notion of
timeout, confirmShutdown() adds a dummy task (WAKEUP_TASK) to wake up
takeTask() immediately and instead sleeps hard-coded 100ms. I'll
address this issue later by modifying takeTask() times out dynamically.
Miscellaneous changes:
SingleThreadEventExecutor.wakeup() now has the default implementation.
Instead of interrupting the current thread, it simply adds a dummy task
(WAKEUP_TASK) to the task queue, which is more elegant and efficient.
NioEventLoop is the only implementation that overrides it. All other
implementations' wakeup()s were removed thanks to this change.
This commit introduces a new API for ByteBuf allocation which fixes
issue #643 along with refactoring of ByteBuf for simplicity and better
performance. (see #62)
A user can configure the ByteBufAllocator of a Channel via
ChannelOption.ALLOCATOR or ChannelConfig.get/setAllocator(). The
default allocator is currently UnpooledByteBufAllocator.HEAP_BY_DEFAULT.
To allocate a buffer, do not use Unpooled anymore. do the following:
ctx.alloc().buffer(...); // allocator chooses the buffer type.
ctx.alloc().heapBuffer(...);
ctx.alloc().directBuffer(...);
To deallocate a buffer, use the unsafe free() operation:
((UnsafeByteBuf) buf).free();
The following is the list of the relevant changes:
- Add ChannelInboundHandler.freeInboundBuffer() and
ChannelOutboundHandler.freeOutboundBuffer() to let a user free the
buffer he or she allocated. ChannelHandler adapter classes implement
is already, so most users won't need to call free() by themselves.
freeIn/OutboundBuffer() methods are invoked when a Channel is closed
and deregistered.
- All ByteBuf by contract must implement UnsafeByteBuf. To access an
unsafe operation: ((UnsafeByteBuf) buf).internalNioBuffer()
- Replace WrappedByteBuf and ByteBuf.Unsafe with UnsafeByteBuf to
simplify overall class hierarchy and to avoid unnecesary instantiation
of Unsafe instances on an unsafe operation.
- Remove buffer reference counting which is confusing
- Instantiate SwappedByteBuf lazily to avoid instantiation cost
- Rename ChannelFutureFactory to ChannelPropertyAccess and move common
methods between Channel and ChannelHandlerContext there. Also made it
package-private to hide it from a user.
- Remove unused unsafe operations such as newBuffer()
- Add DetectionUtil.canFreeDirectBuffer() so that an allocator decides
which buffer type to use safely
