Motivation:
We need to ensure we not hold a lock while executor callHandlerRemoved(...) as this may lead to a deadlock if handlerRemoved(...) will call another method in DEfaultChannelPipeline from another thread that will need to obtain the lock as well and wait for the result.
Modifications:
Release the lock before call handlerRemoved0(...).
Result:
No more deadlock possible
Motivation:
We not correctly catched errors during resolving in bootstrap and so may not have notified the future correctly.
Modifications:
Move code into try / catch block and try to fail the promise.
Result:
Promise is always notified
Motivation:
The user may specify to use a different allocator then the default. In this case we need to ensure it is shared when creating the EmbeddedChannel inside of a ChannelHandler
Modifications:
Use the config of the "original" Channel in the EmbeddedChannel and so share the same allocator etc.
Result:
Same type of buffers are used.
Motivation:
There is a small race while adding handlers to the pipeline because callHandlerAddedForAllHandlers() may not be run when the user calls add* but the Channel is already registered.
Modifications:
Ensure we always delay handlerAdded(..) / handlerRemoved(...) until callHandlerAddedForAllHandlers() was called.
Result:
No more race on pipeline modifications possible.
Motivation:
We can remove the volatile keyword from the cached Runnables as at worse these will just be re-created.
Modifications:
Remove volatile.
Result:
Less overhead.
Motivation:
SingleThreadEventExecutor.pendingTasks() will call taskQueue.size() to get the number of pending tasks in the queue. This is not safe when using MpscLinkedQueue as size() is only allowed to be called by a single consumer.
Modifications:
Ensure size() is only called from the EventLoop.
Result:
No more livelock possible when call pendingTasks, no matter from which thread it is done.
Motivation:
While doing 8fe3c83e4c I made a change which disallowed using null as name for handlers in the pipeline (this generated a new name before).
Modifications:
Revert to old behaviour and adding test case.
Result:
Allow null name again
Motivation:
At the moment the user is responsible to increase the writer index of the composite buffer when a new component is added. We should add some methods that handle this for the user as this is the most popular usage of the composite buffer.
Modifications:
Add new methods that autoamtically increase the writerIndex when buffers are added.
Result:
Easier usage of CompositeByteBuf.
Motivation:
EventLoopGroup.register doesn't need the Channel paramter when ChannelPromise is provided as we can get the Channel from ChannelPromise. Resolves#2422.
Modifications:
- Add EventLoopGroup.register(ChannelPromise)
- Deprecate EventLoopGroup.register(Channel, ChannelPromise)
Result:
EventLoopGroup.register is more convenient as people only need to set one parameter.
Motivation:
DefaultChannelPipeline was tightly coupled to AbstractChannel which is not really needed.
Modifications:
Move logic of calling handlerAdded(...) for handlers that were added before the Channel was registered to DefaultChannelPipeline by making it part of the head context.
Result:
Less coupling and so be able to use DefaultChannelPipeline also with other Channel implementations that not extend AbstractChannel
Motivation:
We do a "blind" cast to AbstractChannel in AbstractChannelHandlerContext which we should better no do. It would be better to decouble AbstractChannelHandlerContext from AbstractChannel.
Modifications:
Decouble AbstractChannelHandlerContext from AbstractChannel by move logic to DefaultChannelPipeline
Result:
Less coubling and less casting.
Motivation:
If the user will use addLast(...) on the ChannelPipeline of EmbeddedChannel after its constructor was run it will break the EmbeddedChannel as it will not be able to collect inbound messages and exceptions.
Modifications:
Ensure addLast(...) work as expected by move the logic of handling messages and exceptions ti protected methods of DefaultChannelPipeline and use a custom implementation for EmbeddedChannel
Result:
addLast(...) works as expected when using EmbeddedChannel.
Motivation:
Recycler.recycle(...) should not be used anymore and be replaced by Handle.recycle().
Modifications:
Mark it as deprecated and update usage.
Result:
Correctly document deprecated api.
Motivation:
The Bootstrap class (applies also to AbstractBootstrap and ServerBootstrap) has a few package private getter methods and some things such as #attr() and #options() aren't exposed at all.
Modifications:
Expose "getters" for configured things in a safe-manner via the config() method.
Result:
Easier for the user to check what is configured for a Bootstrap/ServerBootstrap.
Motivation:
The DuplexChannel is currently incomplete and only supports shutting down the output side of a channel. This interface should also support shutting down the input side of the channel.
Modifications:
- Add shutdownInput and shutdown methods to the DuplexChannel interface
- Remove state in NIO and OIO for tracking input being shutdown independent of the underlying transport's socket type. Tracking the state independently may lead to inconsistent state.
Result:
DuplexChannel supports shutting down the input side of the channel
Fixes https://github.com/netty/netty/issues/5175
Motivation:
When a user has multiple EventLoops in an EventLoopGroup and calls pipeline.add* / remove* / replace from an EventLoop that belongs to another Channel it is possible to deadlock if the other EventLoop does the same.
Modification:
- Only ensure the actual modification takes place in a synchronized block and not wait until the handlerAdded(...) / handlerRemoved(...) method is called. This is ok as we submit the task to the executor while still holding the look and so ensure correct order of pipeline modifications.
- Ensure if an AbstractChannelHandlerContext is put in the linked-list structure but the handlerAdded(...) method was not called we skip it until handlerAdded(...) was called. This is needed to ensure handlerAdded(...) is always called first.
Result:
Its not possible to deadlock when modify the DefaultChannelPipeline.
Related: #4333#4421#5128
Motivation:
slice(), duplicate() and readSlice() currently create a non-recyclable
derived buffer instance. Under heavy load, an application that creates a
lot of derived buffers can put the garbage collector under pressure.
Modifications:
- Add the following methods which creates a non-recyclable derived buffer
- retainedSlice()
- retainedDuplicate()
- readRetainedSlice()
- Add the new recyclable derived buffer implementations, which has its
own reference count value
- Add ByteBufHolder.retainedDuplicate()
- Add ByteBufHolder.replace(ByteBuf) so that..
- a user can replace the content of the holder in a consistent way
- copy/duplicate/retainedDuplicate() can delegate the holder
construction to replace(ByteBuf)
- Use retainedDuplicate() and retainedSlice() wherever possible
- Miscellaneous:
- Rename DuplicateByteBufTest to DuplicatedByteBufTest (missing 'D')
- Make ReplayingDecoderByteBuf.reject() return an exception instead of
throwing it so that its callers don't need to add dummy return
statement
Result:
Derived buffers are now recycled when created via retainedSlice() and
retainedDuplicate() and derived from a pooled buffer
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:
If a task was submitted when wakenUp value was true, the task didn't get a chance to call Selector#wakeup.
So we need to check task queue again before executing select operation. If we don't, the task might be pended until select operation was timed out.
It might be pended until idle timeout if IdleStateHandler existed in pipeline.
Modifications:
Execute Selector#select in a non-blocking manner if there's a task submitted when wakenUp value was true.
Result:
Every tasks in NioEventLoop will not be pended.
Motivation:
Users sometimes want to use Channel.voidPromise() when write to a Channel to reduce GC-pressure. This should be also possible when write via a ChannelGroup.
Modifications:
Add new write(...) and writeAndFlush(...) overloads which allow to signale that a VoidPromise should be used to write to the Channel
Result:
Users can write with VoidPromise when using ChannelGroup
Motivation:
ChannelHandlerContext, ChannelPipeline and Channel share various method signatures. We should provide an interface to share.
Modifications:
Add ChannelInboundInvoker and ChannelOutboundInvoker and extend these.
Result:
Better API abstraction.
Motivation:
To be more consistent we should use ConnectException when we fail the connect attempt because no LocalServerChannel exists with the given address.
Modifications:
Use correct exception.
Result:
More consistent handling of connection refused between different transports.
Motivation:
Bootstrap.connect(...) tries to obtain the EventLoop of a Channel before it may be registered. This will cause an IllegalStateException. We need to ensure we handle the cause of late registration and not throw in this case.
Modifications:
Ensure we only try to access the EventLoop after the Channel is registered and handle the case of late registration.
Result:
Bootstrap.connect(...) not fails on late registration.
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:
The ChannelHandlerContext.attr(...) and ChannelHandlerContext.hasAttr(...) delegated to Channel for the attributes which is a semantic change compared to 4.0 releases. We should not change the semantic to not break users applications when upgrading to 4.1.0
Modifications:
- Revert semantic change
- Mark ChannelHandlerContext.attr(...) and hasAttr(...) as @deprecated so we can remove these later
Result:
Semantic of attribute operations on ChannelHandlerContext is the same in 4.1 as in 4.0 again.
Motivation:
We should not try to call bind if registration failed.
Modifications:
Only call doBind0(...) when the registration not failed.
Result:
Not try to to bind if the registration failed.
Motivation:
We use channel.unsafe().invoker().executor() in DefaultChannelPipeline.executorSafe(...) which is an unnecessary indirection to channel.eventLoop().
Modifications:
Remove indirection by using channel.eventLoop().
Result:
Cleaner code.
Motivation:
NioDatagramChannelConfig currently uses NetworkChannel in its static { } block and so fails to init on android which not has this class.
Modifications:
Use reflection to load the NetworkChannel.class
Result:
Be able to use NIO Datagram on android as well.
Motivation:
We may produce a NPE due a race that can happen while check if a resolution was done and failed.
Modifications:
Correctly first check if the resultion is done before try to detect if it failed and so remove the race that can produce a NPE.
Result:
No more race possible while resolve address during connect.
Motivation:
Reduce nag warnings when compiling, make it easier for IDEs to display what's deprecated.
Modifications:
Added @Deprecated in a few places
Result:
No more warnings.
Motivation:
If a channel is deregistered from an NioEventLoop the associated SelectionKey is cancelled. If the NioEventLoop has yet to process a pending event as a result of that SelectionKey then the NioEventLoop will see the SelecitonKey is invalid and close the channel. The NioEventLoop should not close a channel if it is not registered with that NioEventLoop.
Modifications:
- NioEventLoop.processSelectedKeys should check that the channel is still registered to itself before closing the channel
Result:
NioEventLoop doesn't close a channel that is no longer registered to it when the SelectionKey is invalid
Fixes https://github.com/netty/netty/issues/5125
Motivation:
Revert d0943dcd30. Delaying the notification of writability change may lead to notification being missed. This is a ABA type of concurrency problem.
Modifications:
- Revert d0943dcd30.
Result:
channelWritabilityChange will be called on every change, and will not be suppressed due to ABA scenario.
Motivation:
Commit 0bc93dd introduced a potential assertion failure, if the deprecated method would be used.
Modifications:
Fix the potential assertion error.
Result:
Regression removed
Motivation:
There is one extra } for WriteBufferWaterMark's javadoc:
{@linkplain #high} high water mark}
The generated javadoc will show the content: "the high high water mark}"
Modifications:
remove the }
Result:
The generated javadoc will show the content: "the high water mark" instead of "the high high water mark}"
Motivation:
Prior to 5b48fc284e setting readPending to false when autoReadClear was called was enough because when/if the EventLoop woke up with a read event we would first check if readPending was true and if it is not, we would return early. Now that readPending will only be set in the EventLoop it is not necessary to check readPending at the start of the read methods, and we should instead remove the OP_READ from the SelectionKey when we also set readPending to false.
Modifications:
- autoReadCleared should call AbstractNioUnsafe.removeReadOp
Result:
NIO is now consistent with EPOLL and removes the READ operation on the selector when autoRead is cleared.
Motivation:
OIO/NIO use a volatile variable to track if a read is pending. EPOLL does not use a volatile an executes a Runnable on the event loop thread to set readPending to false. These mechansims should be consistent, and not using a volatile variable is preferable because the variable is written to frequently in the event loop thread.
OIO also does not set readPending to false before each fireChannelRead operation and may result in reading more data than the user desires.
Modifications:
- OIO/NIO should not use a volatile variable for readPending
- OIO should set readPending to false before each fireChannelRead
Result:
OIO/NIO/EPOLL are more consistent w.r.t. readPending and volatile variable operations are reduced
Fixes https://github.com/netty/netty/issues/5069
Motivation:
When always triggered fireChannelWritabilityChanged() directly when the update the pending bytes in the ChannelOutboundBuffer was made from within the EventLoop. This is problematic as this can cause some re-entrance issue if the user has a custom ChannelOutboundHandler that does multiple writes from within the write(...) method and also has a handler that will intercept the channelWritabilityChanged event and trigger another write when the Channel is writable. This can also easily happen if the user just use a MessageToMessageEncoder subclass and triggers a write from channelWritabilityChanged().
Beside this we also triggered fireChannelWritabilityChanged() too often when a user did a write from outside the EventLoop. In this case we increased the pending bytes of the outboundbuffer before scheduled the actual write and decreased again before the write then takes place. Both of this may trigger a fireChannelWritabilityChanged() event which then may be re-triggered once the actual write ends again in the ChannelOutboundBuffer.
The third gotcha was that a user may get multiple events even if the writability of the channel not changed.
Modification:
- Always invoke the fireChannelWritabilityChanged() later on the EventLoop.
- Only trigger the fireChannelWritabilityChanged() if the channel is still active and if the writability of the channel changed. No need to cause events that were already triggered without a real writability change.
- when write(...) is called from outside the EventLoop we only increase the pending bytes in the outbound buffer (so that Channel.isWritable() is updated directly) but not cause a fireChannelWritabilityChanged(). The fireChannelWritabilityChanged() is then triggered once the task is picked up by the EventLoop as usual.
Result:
No more re-entrance possible because of writes from within channelWritabilityChanged(...) method and no events without a real writability change.
Motivation:
441aa4c575 introduced a bug in transport-native-epoll where readPending is set to false before a read is attempted, but this should happen before fireChannelRead is called. The NIO transport also only sets the readPending variable to false on the first read in the event loop. This means that if the user only calls read() on the first channelRead(..) the select loop will still listen for read events even if the user does not call read() on subsequent channelRead() or channelReadComplete() in the same event loop run. If the user only needs 2 channelRead() calls then by default they will may get 14 more channelRead() calls in the current event loop, and then 16 more when the event loop is woken up for a read event. This will also read data off the TCP stack and allow the peer to queue more data in the local RECV buffers.
Modifications:
- readPending should be set to false before each call to channelRead()
- make NIO readPending set to false consistent with EPOLL
Result:
NIO and EPOLL transport set readPending to false at correct times which don't read more data than intended by the user.
Fixes https://github.com/netty/netty/issues/5082
Motivation:
When a promise is notified that was already added to the ChannelOutboundBuffer and we try to notify it later on we only see a warning that it was notified before. This is often not very useful as we have no idea where it was notified at all. We can do better in case it was failed before (which is most of the times the case) and just also log the cause that was used for it.
Modifications:
Add the cause that was used to notify the promise when we fail to notify it as part of the ChannelOutboundBuffer.
Result:
Easier to debug user errors.
Motivation:
There is a spelling error in FileRegion.transfered() as it should be transferred().
Modifications:
Deprecate old method and add a new one.
Result:
Fix typo and can remove the old method later.
Motivation:
DefaultChannelHandlerInvoker currently blindly cast to AbstractChannelHandlerContext without checking if the ChannelHandlerContext is really a sub-type of it. It should check it first and if not just use slow-path implementation.
Modifications:
Do instanceof check first and if it fails just create a new Runnable instance of used the cached.
Result:
DefaultChannelHandlerInvoker works with any ChannelHandlerContext implementations.
Motivation:
Setting the WRITE_BUFFER_LOW_WATER_MARK before WRITE_BUFFER_HIGH_WATER_MARK results in an internal Exception (appears only in the logs) if the value is larger than the default high water mark value. The WRITE_BUFFER_HIGH_WATER_MARK call appears to have no effect in this context.
Setting the values in the reverse order works.
Modifications:
- deprecated ChannelOption.WRITE_BUFFER_HIGH_WATER_MARK and
ChannelOption.WRITE_BUFFER_LOW_WATER_MARK.
- add one new option called ChannelOption.WRITE_BUFFER_WATER_MARK.
Result:
The high/low water mark values limits caused by default values are removed.
Setting the WRITE_BUFFER_LOW_WATER_MARK before WRITE_BUFFER_HIGH_WATER_MARK results in an internal Exception (appears only in the logs) if the value is larger than the default high water mark value. The WRITE_BUFFER_HIGH_WATER_MARK call appears to have no effect in this context.
Setting the values in the reverse order works.
Motivation:
If a handler is added to the pipeline within ChannelInitializer::initChannel via
addFirst(...) then it will not receive the channelRegistered event. The same
handler added via addLast(...) will receive the event. This different behavior
is unlikely to be expected by users and can cause confusion.
Modifications:
Let ChannelInitializer::channelRegistered propagate the event by passing it to
the pipeline instead of firing it on the ChannelHandlerContext.
Result:
The channelRegistered event is propagated to handlers regardless of the method
used to add it to the pipeline (addFirst/addLast).
Motivation:
NIO now supports a pluggable select strategy, but EPOLL currently doesn't support this. We should strive for feature parity for EPOLL.
Modifications:
- Add SelectStrategy to EPOLL transport.
Result:
EPOLL transport supports SelectStategy.
Motivation:
Under high throughput/low latency workloads, selector wakeups are
degrading performance when the incoming operations are triggered
from outside of the event loop. This is a common scenario for
"client" applications where the originating input is coming from
application threads rather from the socket attached inside the
event loops.
As a result, it can be desirable to defer the blocking select
so that incoming tasks (write/flush) do not need to wakeup
the selector.
Modifications:
This changeset adds the notion of a generic SelectStrategy which,
based on its contract, allows the implementation to optionally
defer the blocking select based on some custom criteria.
The default implementation resembles the original behaviour, that
is if tasks are in the queue `selectNow()` and move on, and if no
tasks need to be processed go into the blocking select and wait
for wakeup.
The strategy can be customized per `NioEventLoopGroup` in the
constructor.
Result:
High performance client applications are now given the chance to
customize for how long the actual selector blocking should be
deferred by employing a custom select strategy.
Motivation:
There is no need to make DefaultChannelId package private as it may be useful for the user. For example EmbeddedChannel allows to inject a ChannelId when it is constructed. For this case the user can just use DefaultChannelId.
Modifications:
Change visibility of DefaultChannelId to public.
Result:
It's possible to create a new instance of DefaultChannelId by the user.
Motivation:
We need to ensure we run all pending tasks before doing any flush in writeOutbound(...) to ensure all pending tasks are run first. Also we should remove the assert of the future and just add a listener to it so it is processed later if needed. This is true as a user may schedule a write for later execution.
Modifications:
- Remove assert of future in writeOutbound(...)
- Correctly run pending tasks before doing the flush and also before doing the close of the channel.
- Add unit tests to proof the defect is fixed.
Result:
Correclty handle the situation of delayed writes.
Motivation:
cf171ff525 introduced a change in behavior when dealing with closing channel in the read loop. This changed behavior may use stale state to determine if a channel should be shutdown and may be incorrect.
Modifications:
- Revert the usage of potentially stale state
Result:
Closing a channel in the read loop is based upon current state instead of potentially stale state.
Motivation:
Often the user uses EmbeddedChannel within unit tests where the only "important" thing is to know if any pending messages were in the buffer and then release these.
We should provide methods for this so the user not need to manually loop through these and release.
Modifications:
Add methods to easily handle releasing of messages.
Result:
Less boiler-plate code for the user to write.
Motivation:
If an error occurs during a write operation then DefaultHttp2ConnectionEncoder.FlowControlledData will clear the CoalescingBufferQueue which will reset the queue's readable bytes to 0. To recover from an error the DefaultHttp2RemoteFlowController will attempt to return bytes to the flow control window, but since the frame has reset its own size this will lead to invalid flow control accounting.
Modifications:
- DefaultHttp2ConnectionEncoder.FlowControlledData should not reset its size if an error occurs
Result:
No more flow controller errors due to DefaultHttp2ConnectionEncoder.FlowControlledData setting its size to 0 if an error occurs.
Motivation:
PromiseAggregator's API allows for the aggregate promise to complete before the user is done adding promises. In order to support this use case the API structure would need to change in a breaking manner.
Modifications:
- Deprecate PromiseAggregator and subclasses
- Introduce PromiseCombiner which corrects these issues
Result:
PromiseCombiner corrects the deficiencies in PromiseAggregator.
Motivation:
PendingWriteQueue should guard against re-entrant writes once
removeAndFailAll() is run.
Modifications:
removeAndFailAll() should repeat until the queue is finally empty.
Result:
assertEmpty() will always hold.
Motivation:
We should guard users from using Unsafe methods from outside the EventLoop if not designed to do so.
Modifications:
Add asserts
Result:
Easier for users to detect miss-use.
Motivation:
DefaultChannelHandlerInvoker.invokeWrite calls a utility method validatePromise which may throw if the arguments are not valid. If this method throws then the message will not be released.
Modifications:
- If an exception is thrown the message should be released
Result:
No more leak in DefaultChannelHandlerInvoker.invokeWrite
Motivation:
See #3746.
Modifications:
Fork SpscLinkedQueue and SpscLinkedAtomicQueue from JCTools based on 7846450e28
Result:
Add SpscLinkedQueue and SpscLinkedAtomicQueue and apply it in LocalChannel.
Motiviation:
We should ensure that handlerAdded(...) and handlerRemoved(...) is always called from the EventExecutor that also invokes the other methods of the ChannelHandler. Also we need to ensure we always call handlerAdded(...) before any other method can be calld to ensure correct ordering.
Motifications:
- Ensure that the right thread is used to call the methods
- Ensure correct ordering
- Add tests
Result:
Respect the thread-model for handlerAdded(...) and handlerRemoved(...) and preserve correct ordering in all cases.
Motivation:
The implementation of obtaining the best possible mac address is very good. There are many sub-par implementations proposed on stackoverflow.
While not strictly a netty concern, it would be nice to offer this util also to netty users.
Modifications:
extract DefaultChannelId#defaultMachineId code obtaining the "best" mac into a new helper called MacAddress, keep the random bytes fallback in DefaultChannelID.
Result:
New helper available.
Motivation:
When a channel was registered before and is re-registered we need to respect ChannelConfig.isAutoRead() and so start reading one the registration task completes. This was done "by luck" before 15162202fb.
Modifications:
Explicit start reading once a Channel was re-registered if isAutoRead() is true.
Result:
Correctly receive data after re-registration completes.
Motivation:
Due a regression introduced by e969b6917c we missed to pass the original ChannelPromise to the next ChannelOutboundHandler and so
may never notify the origin ChannelPromise. This is related to #4805.
Modifications:
- Correctly pass the ChannelPromise
- Add unit test.
Result:
Correctly pass the ChannelPromise on deregister(...)
Motivation:
fix the issue netty#2944
Modifications:
use - instead of =>, use ! instead of :> due to the connection is bidirectional. What's more, toString() method don't know the direction or there is no need to know the direction when only log channel information.
add L： before local address and R: before remote address.
Result:
after the fix, log won't confuse the user
Motivation:
The AbstractChannel(Channel parent) constructor was previously hard-coded to always
call DefaultChannelId.newInstance(), and this made it difficult to use a custom
ChannelId implementation with some commonly used Channel implementations.
Modifications:
Introduced newId() method in AbstractChannel, which by default returns
DefaultChannelId.newInstance() but can be overridden by subclasses. Added
ensureDefaultChannelId() test to AbstractChannelTest, to ensure the prior
behavior of calling DefaultChannelId.newInstance() still holds with the
AbstractChannel(Channel parent) constructor.
Result:
AbstractChannel now has the protected newId() method, but there is no functional
difference.
Motivation:
A few implementations of OioServerChannel have a default max messages per read set to 16. We should set the default to 1 to prevent blocking on a read before setting a socket that has just been accepted.
Modifications:
- OioSctpServerChannel and OioServerSocketChannel metadata changed to use the default (1) max messages per read
Result:
Oio based servers will complete accepting a socket before potentially blocking waiting to accept other sockets.
Motivation:
If a user adds a ChannelHandler from outside the EventLoop it is possible to get into the situation that handlerAdded(...) is scheduled on the EventLoop and so called after another methods of the ChannelHandler as the EventLoop may already be executing on this point in time.
Modification:
- Ensure we always check if the handlerAdded(...) method was called already and if not add the currently needed call to the EventLoop so it will be picked up after handlerAdded(...) was called. This works as if the handler is added to the ChannelPipeline from outside the EventLoop the actual handlerAdded(...) operation is scheduled on the EventLoop.
- Some cleanup in the DefaultChannelPipeline
Result:
Correctly order of method executions of ChannelHandler.
Motivation:
ChannelOutboundHandlerAdapter's javadoc has some minor issues.
Modifications:
Fix the minor javadoc issues and resolves#4752.
Result:
ChannelOutboundHandlerAdapter's javadoc issues are fixed.
Motivation:
Being able to access the invoker() is useful when adding additional
handlers that should be running in the same thread. Since an application
may be using a threading model unsupported by the default invoker, they
can specify their own. Because of that, in a handler that auto-adds
other handlers:
// This is a good pattern
ctx.pipeline().addBefore(ctx.invoker(), ctx.name(), null, newHandler);
// This will generally work, but prevents using custom invoker.
ctx.pipeline().addBefore(ctx.executor(), ctx.name(), null, newHandler);
That's why I believe in commit 110745b0, for the now-defunct 5.0 branch,
when ChannelHandlerAppender was added the invoker() method was also
necessary.
There is a side-benefit to exposing the invoker: in certain advanced
use-cases using the invoker for a particular handler is useful. Using
the invoker you are able to invoke a _particular_ handler, from possibly
a different thread yet still using standard exception processing.
ChannelHandlerContext does part of that, but is unwieldy when trying to
invoke a particular handler because it invokes the prev or next handler,
not the one the context is for. A workaround is to use the next or prev
context (respectively), but this breaks when the pipeline changes.
This came up during writing the Http2MultiplexCodec which uses a
separate child channel for each http/2 stream and wants to send messages
from the child channel directly to the Http2MultiplexCodec handler that
created it.
Modifications:
Add the invoker() method to ChannelHandlerContext. It was already being
implemented by AbstractChannelHandlerContext. The two other
implementations of ChannelHandlerContext needed minor tweaks.
Result:
Access to the invoker used for a particular handler, for either reusing
for other handlers or for advanced use-cases. Fixes#4738
Motivation:
ChannelInboundHandler and ChannelOutboundHandler both can implement exceptionCaught(...) method and so we need to dispatch to both of them.
Modifications:
- Correctly first dispatch exceptionCaught to the ChannelInboundHandler but also make sure the next handler it will be dispatched to will be the ChannelOutboundHandler
- Add removeInboundHandler() and removeOutboundHandler() which allows to remove one of the combined handlers
- Let *Codec extends it and not ChannelHandlerAppender
- Remove ChannelHandlerAppender
Result:
Correctly handle events and also have same behavior as in 4.0
Motivation:
Our contract in Channels is that the promise should always be notified before the actual callbacks of the ChannelInboundHandler are called. This was not done in the LocalChannel and so the behavior was different to other Channel implementations.
Modifications:
- First complete the ChannelPromise then call fireChannelActive()
- Guard against NPE when doClose() was called before the task was executed.
Result:
Consistent behavior between LocalChannel and other Channel implementations.
Motivation:
At the moment EmbeddedChannel always handle close() and disconnect() the same way which also means that ChannelOutboundHandler.disconnect(...) will never called. We should allow to specify if these are handle different or not to make the use of EmbeddedChannel more flexible.
Modifications:
Add 2 other constructors which allow to specify if disconnect / close are handled the same way or differently.
Result:
More flexible usage of EmbeddedChannel possible.
Motivation:
Boxing/unboxing can be avoided.
Modifications:
Use parseInt/parseLong to avoid unnecessary boxing/unboxing.
Result:
Remove unnecessary boxing/unboxing.
Motivation:
The prefix fix of #2363 did not correctly handle the case when selectAgain is true and so missed to null out entries.
Modifications:
Move the i++ from end of loop to beginning of loop
Result:
Entries in the array will be null out so allow to have these GC'ed once the Channel close
Motivation:
We often used synchronized(this) while the whole method was synchronized, which can be simplified by just mark the whole method as synchronized.
Modifications:
Replace synchronized(this) with synchronized on the method
Result:
Cleaner code
Motivation:
Warnings in IDE, unclean code, negligible performance impact.
Modification:
Deletion of unused imports
Result:
No more warnings in IDE, cleaner code, negligible performance improvement.
Motivation:
Javadoc reports errors about invalid docs.
Modifications:
Fix some errors reported by javadoc.
Result:
A lot of javadoc errors are fixed by this patch.
Motivation:
There are some wrong links and tags in javadoc.
Modifications:
Fix the wrong links and tags in javadoc.
Result:
These links will work correctly in javadoc.
Motivation:
As a user may call deregister() from within any method while doing processing in the ChannelPipeline, we need to ensure we do the actual deregister operation later. This is needed as for example, we may be in the ByteToMessageDecoder.callDecode(...) method and so still try to do processing in the old EventLoop while the user already registered the Channel to a new EventLoop. Without delay, the deregister operation this could lead to have a handler invoked by different EventLoop and so threads.
Modifications:
Ensure the actual deregister will be done later on and not directly when invoked.
Result:
Calling deregister() within ByteToMessageDecoder.decode(..) is safe.
Motivation:
Estimation algorithm currently used for WriteTasks is complicated and
wrong. Additionally, some code relies on outbound buffer size
incremented only on actual writes to the outbound buffer.
Modifications:
- Throw away the old estimator and replace with a simple algorithm that
uses the client-provided estimator along with a statically configured
WriteTask overhead (io.netty.transport.writeTaskSizeOverhead system
property with the default value of 48 bytes)
- Add a io.netty.transport.estimateSizeOnSubmit boolean system property
allowing the clients to disable the message estimation outside the
event loop
Result:
Task estimation is user controllable and produces better results by
default
Motivation:
As discussed in #4529, NameResolver design shouldn't be resolving SocketAddresses (or String name + port) and return InetSocketAddresses. It should resolve String names and return InetAddresses.
This SocketAddress to InetSocketAddresses resolution is actually a different concern, used by Bootstrap.
Modifications:
Extract SocketAddress to InetSocketAddresses resolution concern to a new class hierarchy named AddressResolver.
These AddressResolvers delegate to NameResolvers.
Result:
Better separation of concerns.
Note that new AddressResolvers generate a bit more allocations because of the intermediate Promise and List<InetAddress>.
Motivation:
We need to remove all registered events for a Channel from the EventLoop before doing the actual close to ensure we not produce a cpu spin when the actual close operation is delayed or executed outside of the EventLoop.
Modifications:
Deregister for events for NIO and EPOLL socket implementations when SO_LINGER is used.
Result:
No more cpu spin.
Motivation:
Fix a race-condition when closing NioSocketChannel or EpollSocketChannel while try to detect if a close executor should be used and the underlying socket was already closed. This could lead to an exception that then leave the channel / in an invalid state and so could lead to side-effects like heavy CPU usage.
Modifications:
Catch possible socket exception while try to get the SO_LINGER options from the underlying socket.
Result:
No more race-condition when closing the channel is possible with bad side-effects.
Motivation:
ChannelMetadata has a field minMaxMessagesPerRead which can be confusing. There are also some cases where static instances are used and the default value for channel type is not being applied.
Modifications:
- use a default value which is set unconditionally to simplify
- make sure static instances of MaxMessagesRecvByteBufAllocator are not used if the intention is that the default maxMessagesPerRead should be derived from the channel type.
Result:
Less confusing interfaces in ChannelMetadata and ChannelConfig. Default maxMessagesPerRead is correctly applied.
Motivation:
The javadocs for ChannelOption.AUTO_CLOSE say the default is false, but the default is currently true.
Modifications:
- Make javadocs consistent with code
Result:
Less confusing docs.
Motivation:
exceptionCaught(...) will only handle inbound exceptions which means it makes not much sense to have it also on ChannelOutboundHandler. Because of this we should move it to ChannelInboundHandler.
Modifications:
Add @deprecated annotation to ChannelHandler.exceptionCaught(...).
Result:
Preapre to cleanup the API in later release.
Motivation:
We should use OneTimeTask where possible to reduce object creation.
Modifications:
Replace Runnable with OneTimeTask
Result:
Less object creation
Motivation:
We not need to store another reference to AbstractChannel as we can access it through DefaultChannelHandlerContext.
Modifications:
Remove reference.
Result:
Cleaner code.
Motivation:
If you start to have 1M+ concurrent connections memory footprint can be come a big issue. We should try to reduce it as much as possible in the core of netty.
Modifications:
- Remove HashMap that was used to store name to ctx mapping. This was only used for validation and access a handler by name. As a pipeline is not expected to be very long (like 100+ handlers) we can just walk the linked list structure to find the ctx with a given name.
Result:
Less memory footprint of the DefaultChannelPipeline.
Motivation:
The previous DefaultChannelPipeline#destroy() implementation, introduced in #3156, is suboptimal as it can cause the for loop to continuously spin if the executor used by a given handler is unable to "recognize" the event loop.
It could be objected that it's the custom executor responsibility to properly implement the inEventLoop() method, but some implementetaions might not be able to do that for performance reasons, and even so, it's always better to be safe against API misuse, in particular when it is not possible to fail fast and the alternative is rather some sutle behaviour.
Modifications:
The patch simply avoids the recursive spin by explicitly passing the "in event loop" condition as a boolean parameter, preserving the same guarantees offered by #3156. A unit test has also been added.
Result:
All channel events are correctly called and no high CPU usage is seen anymore.
Motivation:
Changing the chache of generated names to use a cache per thread. This will remove the bottleneck when many eventloops are used and names need to generate.
Modifications:
Use a FastThreadLocal to store the cached names.
Result:
Less locking between threads.
Motivation:
We should only call ReferenceCountUtil.touch(...) if needed as otherwise we pay the overhead of instanceof and cast
everytime.
Modifications:
Add boolean flag which indicates if touch(...) should be called.
Result:
Less overhead when leak detection is not enabled.
