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
- Add Bootstrap.attr() and ServerBootstrap.attr()/childAttr() so that a
user can initialize the attribute map from the beginning.
- Replace newBootstrap() with duplicate()
- Ensure the event loop threads are never terminated before all tasks
submitted by JDK are executed
- Close all open connections before terminating an event loop
- Add ChannelOption.ALLOW_HALF_CLOSURE
- If true, ChannelInputShutdownEvent is fired via userEventTriggered()
when the remote peer shuts down its output, and the connection is
not closed until a user calls close() explicitly.
- If false, the connection is closed immediately as it did before.
- Add SocketChannel.isInputShutdown()
- Add & improve test cases related with half-closed sockets
- Use copy-on-write map
- Fix a potential bug where the old implementation assumed that one
Runnable type always wraps the same Runnable
- Cache offset value instead of Field in UnsafeAioChannelFinder
- Reimplemented the test
- Fixed various bugs related with read/accept suspension found while testing
- defaultInterestOps of NioServerSocketChannel should be OP_ACCEPT
- There's no need do deregister and re-register to suspend/resume accept()
- Occational infinite loop with 100% CPU consumption in OioEventLoop, caused by OioSocketChannel
- Even if read/accept is suspended, what's read or accepted should be notified to a user
- Clean up
- Do not stop reading when reached at maxCapacity.
- Just let handler drain the buffer and try again quickly.
- No more magic number in OIO buffer expansion
- Remove polling in SingleThreadEventExecutor
- Create a dedicated scheduled task scheduler called 'TaskScheduler'
- TaskScheduler is created per EventLoopGroup / EventExecutorGroup
- SingleThreadEventExecutor delegates all scheduled execution requests
to TaskScheduler provided as a constructor parameter
- TaskScheduler is a specialized form of single threaded
ScheduledExecutorService which requires an EventExecutor as a
parameter for all requests.
o Add ByteBuf.hasNioBuffers() method
o Promote CompositeByteBuf.nioBuffers() methods to ByteBuf
o Use ByteBuf.nioBuffers() methods from AioSocketChannel
- Add EventExecutorGroup and EventLoopGroup
- EventExecutor and EventLoop extends EventExecutorGroup and
EventLoopGroup
- They form their own group so that .next() returns itself.
- Rename Bootstrap.eventLoop() to group()
- Rename parameter names such as executor to group
- Rename *EventLoop/Executor to *EventLoop/ExecutorGroup
- Rename *ChildEventLoop/Executor to *EventLoop/Executor
