* Decouble EventLoop details from the IO handling for each transport to allow easy re-use of code and customization
Motiviation:
As today extending EventLoop implementations to add custom logic / metrics / instrumentations is only possible in a very limited way if at all. This is due the fact that most implementations are final or even package-private. That said even if these would be public there are the ability to do something useful with these is very limited as the IO processing and task processing are very tightly coupled. All of the mentioned things are a big pain point in netty 4.x and need improvement.
Modifications:
This changeset decoubled the IO processing logic from the task processing logic for the main transport (NIO, Epoll, KQueue) by introducing the concept of an IoHandler. The IoHandler itself is responsible to wait for IO readiness and process these IO events. The execution of the IoHandler itself is done by the SingleThreadEventLoop as part of its EventLoop processing. This allows to use the same EventLoopGroup (MultiThreadEventLoupGroup) for all the mentioned transports by just specify a different IoHandlerFactory during construction.
Beside this core API change this changeset also allows to easily extend SingleThreadEventExecutor / SingleThreadEventLoop to add custom logic to it which then can be reused by all the transports. The ideas are very similar to what is provided by ScheduledThreadPoolExecutor (that is part of the JDK). This allows for example things like:
* Adding instrumentation / metrics:
* how many Channels are registered on an SingleThreadEventLoop
* how many Channels were handled during the IO processing in an EventLoop run
* how many task were handled during the last EventLoop / EventExecutor run
* how many outstanding tasks we have
...
...
* Implementing custom strategies for choosing the next EventExecutor / EventLoop to use based on these metrics.
* Use different Promise / Future / ScheduledFuture implementations
* decorate Runnable / Callables when submitted to the EventExecutor / EventLoop
As a lot of functionalities are folded into the MultiThreadEventLoopGroup and SingleThreadEventLoopGroup this changeset also removes:
* AbstractEventLoop
* AbstractEventLoopGroup
* EventExecutorChooser
* EventExecutorChooserFactory
* DefaultEventLoopGroup
* DefaultEventExecutor
* DefaultEventExecutorGroup
Result:
Fixes https://github.com/netty/netty/issues/8514 .
Motivation:
We can use the diamond operator these days.
Modification:
Use diamond operator whenever possible.
Result:
More modern code and less boiler-plate.
Motivation:
Found performance issues via FindBugs and PMD.
Modifications:
- Removed unnecessary boxing/unboxing operations in DefaultTextHeaders.convertToInt(CharSequence) and DefaultTextHeaders.convertToLong(CharSequence). A boxed primitive is created from a string, just to extract the unboxed primitive value.
- Added a static modifier for DefaultHttp2Connection.ParentChangedEvent class. This class is an inner class, but does not use its embedded reference to the object which created it. This reference makes the instances of the class larger, and may keep the reference to the creator object alive longer than necessary.
- Added a static compiled Pattern to avoid compile it each time it is used when we need to replace some part of authority.
- Improved using of StringBuilders.
Result:
Performance improvements.
- Related issue: #1432
- Add Future.isCancellable()
- Add Promise.setUncancellable() which is meant to be used for the party that runs the task uncancellable once started
- Implement Future.isCancelled() and Promise.cancel(boolean) properly
