Motivation:
In commit f984870ccc I made a change which operated under invalide assumption that tasks executed by an EventExecutor will always be processed in a serial fashion. This is true for SingleThreadEventExecutor sub-classes but not part of the EventExecutor interface contract.
Because of this change implementations of EventExecutor which not strictly execute tasks in a serial fashion may miss events before handlerAdded(...) is called. This is strictly speaking not correct as there is not guarantee in this case that handlerAdded(...) will be called as first task (as there is no ordering guarentee).
Cassandra itself ships such an EventExecutor implementation which has no strict ordering to spread load across multiple threads.
Modifications:
- Add new OrderedEventExecutor interface and let SingleThreadEventExecutor / EventLoop implement / extend it.
- Only expose "restriction" of skipping events until handlerAdded(...) is called for OrderedEventExecutor implementations
- Add ThreadPoolEventExecutor implementation which executes tasks in an unordered fashion. This is used in added unit test but can also be used for protocols which not expose an strict ordering.
- Add unit test.
Result:
Resurrect the possibility to implement an EventExecutor which does not enforce serial execution of events and be able to use it with the DefaultChannelPipeline.
Motivation:
We tried to provide the ability for the user to change the semantics of the threading-model by delegate the invoking of the ChannelHandler to the ChannelHandlerInvoker. Unfortunually this not really worked out quite well and resulted in just more complexity and splitting of code that belongs together. We should remove the ChannelHandlerInvoker again and just do the same as in 4.0
Modifications:
Remove ChannelHandlerInvoker again and replace its usage in Http2MultiplexCodec
Result:
Easier code and less bad abstractions.
Motivation:
While the default thread model provided by Netty is reasonable enough for most applications, some users might have a special requirement for the thread model. Here are a few examples:
- A user might want to invoke handlers from the caller thread directly, assuming that his or her application is completely asynchronous and does not make any invocation from non-I/O thread. In this case, the default invoker implementation will only add the overhead of checking if the current thread is an I/O thread or not.
- A user might want to invoke handlers from different threads depending on the type of events flexibly.
Modifications:
- Backport 132af3a485 which is a fix for #1912
- Add a new interface called 'ChannelHandlerInvoker' that performs the invocation of event handler methods.
- Add pipeline manipulation methods that accept ChannelHandlerInvoker
- The differences from the original commit:
- Separated the irrelevant changes out
- Channel.eventLoop is null until the registration is complete in this branch, so Channel.Unsafe.invoker() doesn't work before registration.
- Deregistration is not gone in this branch, so the methods related with deregistration were added to ChannelHandlerInvoker
- 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
- Add EventExecutor and make EventLoop extend it
- Add SingleThreadEventExecutor and MultithreadEventExecutor
- Add EventExecutor's default implementation
- Fixed an API design problem where there is no way to get non-bypass
buffer of desired type
- SingleThreadEventLoop now implements ScheduledExecutorService
- Scheduled tasks are automatically fetched into taskQueue by
pollTask() and takeTask()
- Removed MapBackedSet because Java 6 provides it
- Optimized AbstractChannelBuffer.discardReadBytes()
- Split ChannelHandlerInvoker into ChannelInboundInvoker and
ChannelOutboundInvoker
- Channel implements ChannelOutboundInvoker
- ChannelOutboundInvoker.nextOut() is now out()
- ChannelOutboundHandlerContext.out() is now prevOut()
- Added the outbound operations without future
parameter to ChannelOutboundInvoker for user convenience
- All async operations which requires a ChannelFuture as a parameter
now returns ChannelFuture for user convenience
- Added ChannelFutureFactory.newVoidFuture() to allow a user specify
a dummy future that is of no use
- I'm unsure if it is actually a good idea to introduce it. It might
go away later.
- Made the contract of AbstractChannel.doXXX() much simpler and moved
all common code up to AbstractChannel.DefaultUnsafe
- Added Channel.isOpen()
- Fixed a bug where MultithreadEventLoop always shut down its child
event loops on construction
- Maybe more changes I don't remember :-)
- Add EventLoopException to wrap the exceptions while an event loop does
something
- Make EventLoop.register() return EventLoop so that the caller knows
the actual EventLoop that will handle the Channel even if the caller
called register() from MultithreadEventLoop
