Motivation:
We can remove some classes and duplication if we add default methods
Modifications:
- Add default methods to EventExecutor / EventExecutorGroup / EventLoop / EventLoopGroup
- Remove code duplication
- Remove AbstractEventExecutorGroup as it is not needed anymore
Result:
Cleanup and removal of code-duplication. Also makes it easier for people to implement their custom executors / groups
Motivation:
We wish to separate these two into clearer write/read interfaces.
In particular, we don't want to be able to add listeners to promises, because it makes it easy to add them out of order.
We can't prevent it entirely, because any promise can be freely converted to a future where listeners can be added.
We can, however, discourage this in the API.
Modification:
The Promise interface no longer extends the Future interface.
Numerous changes to make the project compile and its tests run.
Result:
Clearer separation of concerns in the code.
Motivation:
NullChecks resulting in a NullPointerException or IllegalArgumentException, numeric ranges (>0, >=0) checks, not empty strings/arrays checks must never be anonymous but with the parameter or variable name which is checked. They must be specific and should not be done with an "OR-Logic" (if a == null || b == null) throw new NullPointerEx.
Modifications:
* Add some checks to ObjectUtil not present today but utilized in the code.
* Add unit test for ObjectUtil
* Update commmons internal usage with ObjectUtil
Result:
All checks needed are present, subsequent changes of usage of ObjectUtil are possible.
Fixes for https://github.com/netty/netty/issues/11170
Motivation:
HTTP is a plaintext protocol which means that someone may be able
to eavesdrop the data. To prevent this, HTTPS should be used whenever
possible. However, maintaining using https:// in all URLs may be
difficult. The nohttp tool can help here. The tool scans all the files
in a repository and reports where http:// is used.
Modifications:
- Added nohttp (via checkstyle) into the build process.
- Suppressed findings for the websites
that don't support HTTPS or that are not reachable
Result:
- Prevent using HTTP in the future.
- Encourage users to use HTTPS when they follow the links they found in
the code.
Motivation:
We should pluck executors in round-robin, but at the 32-bit overflow boundary, the round-robin sequence was disrupted when the number of executors are not a power of 2.
Modifications:
Changed the index counter from a 32-bit to a 64-bit long. The overflow bug is still technically there, but it now takes so long to reach that it will never happen in practice. For example, 2^63 nanoseconds is almost 300 years.
Result:
The round-robin behaviour is now preserved in practice. This is a backport of https://github.com/netty/netty/pull/10468
Motivation:
We can use lambdas now as we use Java8.
Modification:
use lambda function for all package, #8751 only migrate transport package.
Result:
Code cleanup.
* 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:
Sometimes it may be benefitially for an user to specify a custom algorithm when choose the next EventExecutor/EventLoop.
Modifications:
Allow to specify a custom EventExecutorChooseFactory that allows to customize algorithm.
Result:
More flexible api.
Motivation:
EventExecutor.children uses generics in such a way that an entire colleciton must be cast to a specific type of object. This interface is not very flexible and is impossible to implement if the EventExecutor type must be wrapped. The current usage of this method also does not have any clear need within Netty. The Iterator interface allows for EventExecutor to be wrapped and forces the caller to make assumptions about types instead of building the assumptions into the interface.
Motivation:
- Remove EventExecutor.children and undeprecate the iterator() interface
Result:
EventExecutor interface has one less method and is easier to wrap.
Motivation:
EventExecutor.iterator() is fixed to return Iterator<EventExecutor> and there's no way to change that as long as we don't extend Iterable. However, a user should have a way to cast the returned set of executors painlessly. Currently, it is only possible with an explicit cast like (Iterator<NioEventLoop>).
Modifications:
Instead, I added a new method called 'children()' which returns an immutable collection of child executors whose method signature looks like the following:
<E extends EventExecutor> Set<E> children();
Result:
A user can now do this:
Set<NioEventLoop> loops = group.children();
for (NioEventLoop l: loops) { ... }
Unfortunately, this is not possible:
for (NioEventLoop l: group.children()) { ... }
However, it's still a gain that a user doesn't need to down-cast explicitly and to add the '@SuppressWarnings` annotation.
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
