Commit Graph

2023 Commits

Author SHA1 Message Date
Norman Maurer
b1c57257af
Correctly calculate the initial size of the LinkedHashMap during DefaultChannelGroup.write* (#10055)
Motivation:

We should not include the number of ServerChannel that are part of the DefaultChannelGroup when specify the initial size of the LinkedHashMap

Modifications:

Only use the number of the non ServerChannel

Result:

Reduce memory-footprint
2020-02-24 19:29:08 +01:00
feijermu
dcd62c2598
Remove the synchronized flag of fillInStackTrace method to improve performance while creating exception instance. (#10033)
Motivation:

The method body of fillInStackTrace method of IllegalStateException class in SimpleChannelPool.java is so simple (just return this) that there is no need to be marked as synchronized.

Modification:

Remove the synchronized flag of fillInStackTrace method.

Result:

It can improve performance slightly while creating a IllegalStateException instance.
2020-02-17 09:52:36 +01:00
feijermu
862efc618c
Remove the synchronized flag of fillInStackTrace method to improve performance while throwing exception. (#10031)
Motivation:

The method body of fillInStackTrace method of TimeoutException class in FixedChannelPool.java is so simple (just return this) that there is no need to be marked as synchronized.

Modification:

Remove the synchronized flag of fillInStackTrace method.

Result:
It can improve performance slightly while throwing a TimeoutException.
2020-02-15 18:30:44 +01:00
Subba Rao Pasupuleti
0e2e17f9a2
Adding pipeline rename handler tests (#10028)
Motivation:

Current pipeline handler replace tests are replacing handler with same name.
we need test that test handler can renamed, old handlers are removed from pipeline.

Modification:

There is coverage missing related to renaming of handlers

Result:

Adds missing tests

Co-authored-by: phani254 <phani254@yahoo.com>
2020-02-14 16:53:09 +01:00
Subba Rao Pasupuleti
ef50cf5696
remove unused shutdownLock (#10010)
Motivation:

This is unused variable

Modification:

removed variable

Result:

Removes unused lock

Co-authored-by: phani254 <phani254@yahoo.com>
2020-02-11 09:57:52 +01:00
Norman Maurer
a6896eae43
NioEventLoopTest.testChannelsRegistered test failure (#10014)
Motivation:

NioEventLoopTest.testChannelsRegistered sometimes fails due a race which is related to how SelectionKey and Selector is implemented in the JDK. In the current implementation it will "lazy" remove SelectionKeys from the Set which means we may still have these included sometimes when we use size() to get the number of SelectionKeys.

Modifications:

Just retry to read the number of registered Channels if we still see 2

Result:

Fixes https://github.com/netty/netty/issues/9895
2020-02-10 20:28:53 +01:00
Norman Maurer
56055f4404
Ensure ChannelOptions are applied in the same order as configured in *Bootstrap (#9998)
Motivation:

https://github.com/netty/netty/pull/9458 changed how we handled ChannelOptions internally to use a ConcurrentHashMap. This unfortunally had the side-effect that the ordering may be affected and not stable anymore. Here the problem is that sometimes we do validation based on two different ChannelOptions (for example we validate high and low watermarks against each other). Thus even if the user specified the options in the same order we may fail to configure them.

Modifications:

- Use again a LinkedHashMap to preserve order
- Add unit test

Result:

Apply ChannelOptions in correct and expected order
2020-02-06 09:02:31 +01:00
root
9b1ea10a12 [maven-release-plugin] prepare for next development iteration 2020-01-13 09:13:53 +00:00
root
136db8680a [maven-release-plugin] prepare release netty-4.1.45.Final 2020-01-13 09:13:30 +00:00
Nick Hill
ba140ac6bc Fix SimpleChannelPoolTest#testCloseAsync() test flake (#9943)
Motivation

This test is failing intermittently and upon inspection has a race
condition.

Modification

Fix race condition by waiting for async release calls to complete prior
to closing the pool.

Result

Hopefully fixed flakey test
2020-01-11 06:03:45 +01:00
root
79d4e74019 [maven-release-plugin] prepare for next development iteration 2019-12-18 08:32:54 +00:00
root
5ddf45a2d5 [maven-release-plugin] prepare release netty-4.1.44.Final 2019-12-18 08:31:43 +00:00
Scott Mitchell
e7091c04d7 Channel Pool LocalAddress initialization and cleanup (#9879)
Motivation:
The Channel Pool tests commonly use the same fixed local address String. This
has been observed to result in test failures if a single test fails and cleanup
is not done properly, or if tests are run in parallel. Also each test should
close any channel pool objects or maps to make sure resources are reclaimed.

Modifications:
- Use a random string for the address on each test to reduce the chance of
  collision.
- close all ChannelPool and ChannelPoolMap objects at the end of each test

Result:
Less likely to observe spurious failures due to LocalAddress collisions and more
complete test cleanup.
2019-12-13 13:45:22 +01:00
Robert Mihaly
af58bfcfb8 Synchronously close pools when closing AbstractChannelPoolMap (#9857)
Motivation:

In #9830 the get/remove/close methods implementation changed to avoid
deadlocks on event loops. The change involved modifying the methods to
close the managed ChannelPools asynchronously and return immediately.
While this behavior might be fine for get/remove, it is changing what
a user expects from a close() method and after returning from close()
there might be still resources open.

Modifications:

This change is a follow-up for #9830 to preserve the synchronous
behavior of the AbstractChannelPoolMap#close() method.

Result:

AbstractChannelPoolMap#close() returns once the managed pools have
been closed.
2019-12-11 09:28:44 +01:00
梦典
66fca3b58e Update ChannelOutboundBuffer.java (#9863)
Motivation:

fix comment of ChannelOutboundBuffer.CHANNEL_OUTBOUND_BUFFER_ENTRY_OVERHEAD

Modifications:

6 (NOT 8) reference fields is right

Result:
Correct comment
2019-12-11 09:26:21 +01:00
时无两丶
0cde4d9cb4 Uniform null pointer check. (#9840)
Motivation:
Uniform null pointer check.

Modifications:

Use ObjectUtil.checkNonNull(...)

Result:
Less code, same result.
2019-12-09 09:47:35 +01:00
Norman Maurer
e69c4173ea
Replace synchronized with ConcurrentHashMap in Http2StreamChannelBootstrap (#9848)
Motivation:

97361fa2c8 replace synchronized with ConcurrentHashMap in *Bootstrap classes but missed to do the same for the Http2 variant.

Modifications:

- Use ConcurrentHashMap
- Simplify code in *Bootstrap classes

Result:

Less contention
2019-12-06 10:59:55 +01:00
Robert Mihaly
a322addb17 Asynchronously close pools in AbstractChannelPoolMap (#8238) (#9830)
Motivation:

In certain scenarios mutliple concurrent AbstractChannelPoolMap
operations might be called from event loops that handle also
ChannelPool close operations. If the map uses synchronous close
it could end up blocking the event loop and if multiple threads
are waiting for each other a deadlock might occur.

Modifications:

Previously #9226 introduced a closeAsync operation for
FixedChannelPool, which is now extended to SimpleChannelPool class.
The AbstractChannelPoolMap now uses the closeAsync operations when
closing redundant or removed SimpleChannelPool instances.

Result:

The AbstractChannelPoolMap get/remove operations will not wait
until the pools are closed as they will happen asynchronously and
avoid situations that could cause the event loop being blocked in
deadlocks.
2019-12-05 09:14:10 +01:00
Nick Hill
6d0c0e991b Small simplification to WriteTask optimization (#9807)
Motiviation

#9800 was just merged which consolidates the flush/no-flush WriteTasks
in AbstractChannelHandlerContext, but after looking at the changes again
I noticed a tiny simplification that would be good to make imo.

Modification

Remove use of conditional operator in decrementPendingOutboundBytes()

Result

Simpler code, one less branch
2019-11-27 06:55:22 +01:00
Nick Hill
e208e96f12 Clean up NioEventLoop (#9799)
Motivation

The event loop implementations had become somewhat tangled over time and
work was done recently to streamline EpollEventLoop. NioEventLoop would
benefit from the same treatment and it is more straighforward now that
we can follow the same structure as was done for epoll.

Modifications

Untangle NioEventLoop logic and mirror what's now done in EpollEventLoop
w.r.t. the volatile selector wake-up guard and scheduled task deadline
handling.

Some common refinements to EpollEventLoop have also been included - to
use constants for the "special" deadline/wakeup volatile values and to
avoid some unnecessary calls to System.nanoTime() on task-only
iterations.

Result

Hopefully cleaner, more efficient and less fragile NIO transport
implementation.
2019-11-26 08:25:59 +01:00
Nick Hill
b413464091 Optimize WriteTask recycling (#9800)
Motivation

AbstractChannelHandlerContext uses recyclable tasks when performing
writes from outside of the event loop. There's currently two distinct
classes WriteTask and WriteAndFlushTask used for executing writes versus
writeAndFlushes, and these are recycled in separate pools. However it is
straightforward to just have a single class / recycler pool, with a
flush flag.

Modifications

- Unify WriteTasks into a single class using the sign bit of the
existing size field to indicate whether a flush should be performed
- Use the new executor lazyExecute() method to lazily execute the
non-flush write tasks explicitly
- Change AbstractChannelHandlerContext#invokeWrite and
AbstractChannelHandlerContext#invokeWriteAndFlush from private to
package-private to avoid synthetic methods
- Correct the default object size estimate for WriteTask

Results

- Possibly improved reuse of recycled write tasks
- Fewer virtual method calls and shorter path lengths
- Less code
2019-11-23 20:45:35 +01:00
stroller
aa2a9931e8 Add one new constructor with threadFactory only (#9773)
Motivation:
In most cases, we want to use MultithreadEventLoopGroup such as NioEventLoopGroup without setting thread numbers but thread name only. So we need to use followed code:
NioEventLoopGroup boss = new NioEventLoopGroup(0, new DefaultThreadFactory("boss"));
It looks a bit confuse or strange for the number 0 due to we only want to set thread name. So it will be better to add new constructor for this case.

Modifications:
add new constructor into all event loop groups, for example: public NioEventLoopGroup(ThreadFactory threadFactory)

Result:
User can only set thread factory without setting the thread number to 0:
NioEventLoopGroup boss = new NioEventLoopGroup(new DefaultThreadFactory("boss"));
2019-11-18 09:42:44 +01:00
Matthew Miller
394e7f0287 Prevent memory leak when SimpleChannelPools are destroyed (#9760)
Motivation:

https://github.com/netty/netty/pull/9548 introduced a change that creates a new AttributeKey
for each SimpleChannelPool instance created. AttributeKeys are cached statically in a ConstantPool
by the AttributeKey.newInstance method. Because of this, creating a SimpleChannelPool instance will
allocate memory that will never be released, even after the SimpleChannelPool is closed.

Modifications:

This change goes back to a single AttributeKey per SimpleChannelPool, just using a more specific
name to reduce the chance of conflicts with user code.

Result:

No memory is leaked after a SimpleChannelPool instance is created and destroyed.
2019-11-07 14:48:56 +01:00
Nick Hill
a18c57ea87 Externalize lazy execution semantic for EventExecutors (#9587)
Motivation

This is already done internally for various reasons but it would make
sense i.m.o. as a top level concept: submitting a task to be run on the
event loop which doesn't need to run immediately but must still be
executed in FIFO order relative all other submitted tasks (be those
"lazy" or otherwise).

It's nice to separate this abstract "relaxed" semantic from concrete
implementations - the simplest is to just delegate to existing execute,
but for the main EL impls translates to whether a wakeup is required
after enqueuing.

Having a "global" abstraction also allows for simplification of our
internal use - for example encapsulating more of the common scheduled
future logic within AbstractScheduledEventExecutor.

Modifications

- Introduce public LazyRunnable interface and
AbstractEventExecutor#lazyExecute method (would be nice for this to be
added to EventExecutor interface in netty 5)
- Tweak existing SingleThreadEventExecutor mechanics to support these
- Replace internal use of NonWakeupRunnable (such as for pre-flush
channel writes)
- Uplift scheduling-related hooks into AbstractScheduledEventExecutor,
eliminating intermediate executeScheduledRunnable method

Result

Simpler code, cleaner and more useful/flexible abstractions - cleaner in
that they fully communicate the intent in a more general way, without
implying/exposing/restricting implementation details
2019-10-31 10:01:53 +01:00
SimpleYoung
82376fd889 Remove an unnecessary expression in NioEventLoop (#9729)
Motivation:

Remove an unnecessary expression to make the code more readable

Modification:

Remove `eventLoop == null`

Result:

Fixes #9725
2019-10-30 12:24:03 +01:00
Norman Maurer
6c061abc49
Hide Recycler implemention to allow experimenting with different implementions of an Object pool (#9715)
Motivation:

At the moment we directly extend the Recycler base class in our code which makes it hard to experiment with different Object pool implementation. It would be nice to be able to switch from one to another by using a system property in the future. This would also allow to more easily test things like https://github.com/netty/netty/pull/8052.

Modifications:

- Introduce ObjectPool class with static method that we now use internally to obtain an ObjectPool implementation.
- Wrap the Recycler into an ObjectPool and return it for now

Result:

Preparation for different ObjectPool implementations
2019-10-26 00:34:30 -07:00
root
844b82b986 [maven-release-plugin] prepare for next development iteration 2019-10-24 12:57:00 +00:00
root
d066f163d7 [maven-release-plugin] prepare release netty-4.1.43.Final 2019-10-24 12:56:30 +00:00
Norman Maurer
6c05d16967
Use @SuppressJava6Requirement for animal sniffer plugin to ensure we always guard correctly (#9655)
Motivation:

We can use the `@SuppressJava6Requirement` annotation to be more precise about when we use Java6+ APIs. This helps us to ensure we always protect these places.

Modifications:

Make use of `@SuppressJava6Requirement` explicit

Result:

Fixes https://github.com/netty/netty/issues/2509.
2019-10-14 15:54:49 +02:00
stroller
deb34a0f8b remove useless doc for 5.0 (#9546)
Fix javadoc issues

Motivation:

Remove useless doc for 5.0

Modifications:

Remove description for 5.0

Result:

Useless doc will be removed.
2019-10-12 20:17:18 +02:00
Nick Hill
99a4cecec6 Fix NioEventLoopTest#testChannelsRegistered flakiness (#9650)
Motivation

NioEventLoopTest#testChannelsRegistered() fails intermittently due to
use of SingleThreadEventLoop#channelsRegistered() which is not
threadsafe and unreliable when called from outside the event loop.

Modifications

Add static registeredChannels method to NioEventLoopTest and
AbstractSingleThreadEventLoopTest to call from the tests via event loop
instead of directly.

Result

Hopefully fewer test failures
2019-10-09 16:57:54 +04:00
Nick Hill
170e4deee6 Fix event loop shutdown timing fragility (#9616)
Motivation

The current event loop shutdown logic is quite fragile and in the
epoll/NIO cases relies on the default 1 second wait/select timeout that
applies when there are no scheduled tasks. Without this default timeout
the shutdown would hang indefinitely.

The timeout only takes effect in this case because queued scheduled
tasks are first cancelled in
SingleThreadEventExecutor#confirmShutdown(), but I _think_ even this
isn't robust, since the main task queue is subsequently serviced which
could result in some new scheduled task being queued with much later
deadline.

It also means shutdowns are unnecessarily delayed by up to 1 second.

Modifications

- Add/extend unit tests to expose the issue
- Adjust SingleThreadEventExecutor shutdown and confirmShutdown methods
to explicitly add no-op tasks to the taskQueue so that the subsequent
event loop iteration doesn't enter blocking wait (as looks like was
originally intended)

Results

Faster and more robust shutdown of event loops, allows removal of the
default wait timeout
2019-10-07 11:06:01 +04:00
Codrut Stancu
4980a6b304 Register sun.nio.ch.SelectorImpl fields for unsafe access. (#9631)
Motivation:

On JDK > 9 Netty uses Unsafe to write two internal JDK fields: sun.nio.ch.SelectorImp.selectedKeys and sun.nio.ch.SelectorImpl.publicSelectedKeys. This is done in transport/src/main/java/io/netty/channel/nio/NioEventLoop.java:225, in openSelector() method. The GraalVM analysis cannot do the Unsafe registration automatically because the object field offset computation is hidden behind two layers of calls.

Modifications:

This PR updates the Netty GraalVM configuration by registering those fields for unsafe access.
 
Result:

Improved support for Netty on GraalVM with JDK > 9.
2019-10-07 10:10:46 +04:00
bruce
b39ffed042 Fix incorrect calculation of next buffer size in AdaptiveRecvByteBufAllocator (#9555)
Motivation:

Due a bug we did not always correctly calculate the next buffer size in AdaptiveRecvByteBufAllocator.

Modification:

Fix calculation and add unit test

Result:

Correct calculation is always used.
2019-09-27 09:59:25 +02:00
root
92941cdcac [maven-release-plugin] prepare for next development iteration 2019-09-25 06:15:31 +00:00
root
bd907c3b3a [maven-release-plugin] prepare release netty-4.1.42.Final 2019-09-25 06:14:31 +00:00
Norman Maurer
3ad037470e
Correctly reset cached local and remote address when disconnect() is called (#9545)
Motivation:

We should correctly reset the cached local and remote address when a Channel.disconnect() is called and the channel has a notion of disconnect vs close (for example DatagramChannel implementations).

Modifications:

- Correctly reset cached kicak abd remote address
- Update testcase to cover it and so ensure all transports work in a consistent way

Result:

Correctly handle disconnect()
2019-09-19 08:51:10 +02:00
stroller
d01282e5f9 Remove duplicated calculation (#9565)
Motivation:

calculateMaxBytesPerGatheringWrite() contains duplicated calculation:  getSendBufferSize() << 1

Modifications:

Remove the duplicated calculation

Result:

The method will be clear and better
2019-09-15 08:05:21 +02:00
root
01d805bb76 [maven-release-plugin] prepare for next development iteration 2019-09-12 16:09:55 +00:00
root
7cf69022d4 [maven-release-plugin] prepare release netty-4.1.41.Final 2019-09-12 16:09:00 +00:00
root
aef47bec7f [maven-release-plugin] prepare for next development iteration 2019-09-12 05:38:11 +00:00
root
267e5da481 [maven-release-plugin] prepare release netty-4.1.40.Final 2019-09-12 05:37:30 +00:00
Nizar Mankulangara
572b6a8f19 SimpleChannelPool POOL_KEY attribute name is easy to get conflict from user code (#9542) (#9548)
Motivation:

    It is noticed that SimpleChannelPool's POOL_KEY attribute name channelPool is easy to get conflict with user code and throws an exception 'channelPool' is already in use. Being a generic framework - it would be great if we can name the attribute something unique - may be use UUID for the name since the name is not required later.

    Modifications:

    This change make sure that the POOL_KEY used inside SimpleChannelPool is unique by appending the object hashcode in the name.

    Result:

    No unwanted channel attribute name conflict with user code.
2019-09-09 09:47:23 +02:00
Nitsan Wakart
d446765b84 Replace synchronized blocks + assert with synchronized method (#9538)
Motivation:

Following up on discussion with @normanmaurer with suggestion to improve code clarity.

Modification:

Method is synchronized, no need for assert or verbose sync blocks around calls.

Result:

Reduce verbosity and more idiomatic use of keyword. Also rename the method to better describe what it's for.
2019-09-05 09:12:16 +02:00
Norman Maurer
affbdf7125
Correctly protect DefaultChannelPipeline nodes when concurrent removals happen due handlerAdded(...) throwing (#9530)
Motivation:

We need to update the doubly-linked list nodes while holding a lock via synchronized in all cases as otherwise we may end-up with a corrupted pipeline. We missed this when calling remove0(...) due handlerAdded(...) throwing an exception.

Modifications:

- Correctly hold lock while update node
- Add assert
- Add unit test

Result:

Fixes https://github.com/netty/netty/issues/9528
2019-09-03 08:35:11 +02:00
Xiaoqin Fu
21b7e29ea7 Remove extra checks to fix #9456 (#9523)
Motivation:

There are some extra log level checks (logger.isWarnEnabled()).

Modification:

Remove log level checks (logger.isWarnEnabled()) from io.netty.channel.epoll.AbstractEpollStreamChannel, io.netty.channel.DefaultFileRegion, io.netty.channel.nio.AbstractNioChannel, io.netty.util.HashedWheelTimer, io.netty.handler.stream.ChunkedWriteHandler and io.netty.channel.udt.nio.NioUdtMessageConnectorChannel

Result:

Fixes #9456
2019-08-30 10:37:30 +02:00
Nick Hill
a22d4ba859 Simplify EventLoop abstractions for timed scheduled tasks (#9470)
Motivation

The epoll transport was updated in #7834 to decouple setting of the
timerFd from the event loop, so that scheduling delayed tasks does not
require waking up epoll_wait. To achieve this, new overridable hooks
were added in the AbstractScheduledEventExecutor and
SingleThreadEventExecutor superclasses.

However, the minimumDelayScheduledTaskRemoved hook has no current
purpose and I can't envisage a _practical_ need for it. Removing
it would reduce complexity and avoid supporting this specific
API indefinitely. We can add something similar later if needed
but the opposite is not true.

There also isn't a _nice_ way to use the abstractions for
wakeup-avoidance optimizations in other EventLoops that don't have a
decoupled timer.

This PR replaces executeScheduledRunnable and
wakesUpForScheduledRunnable
with two new methods before/afterFutureTaskScheduled that have slightly
different semantics:
 - They only apply to additions; given the current internals there's no
practical use for removals
 - They allow per-submission wakeup decisions via a boolean return val,
which makes them easier to exploit from other existing EL impls (e.g.
NIO/KQueue)
 - They are subjectively "cleaner", taking just the deadline parameter
and not exposing Runnables
 - For current EL/queue impls, only the "after" hook is really needed,
but specialized blocking queue impls can conditionally wake on task
submission (I have one lined up)

Also included are further optimization/simplification/fixes to the
timerFd manipulation logic.

Modifications

- Remove AbstractScheduledEventExecutor#minimumDelayScheduledTaskRemoved()
and supporting methods
- Uplift NonWakeupRunnable and corresponding default wakesUpForTask()
impl from SingleThreadEventLoop to SingleThreadEventExecutor
- Change executeScheduledRunnable() to be package-private, and have a
final impl in SingleThreadEventExecutor which triggers new overridable
hooks before/afterFutureTaskScheduled()
- Remove unnecessary use of bookend tasks while draining the task queue
- Use new hooks to add simpler wake-up avoidance optimization to
NioEventLoop (primarily to demonstrate utility/simplicity)
- Reinstate removed EpollTest class

In EpollEventLoop:
 - Refactor to use only the new afterFutureTaskScheduled() hook for
updating timerFd
 - Fix setTimerFd race condition using a monitor
 - Set nextDeadlineNanos to a negative value while the EL is awake and
use this to block timer changes from outside the EL. Restore the
known-set value prior to sleeping, updating timerFd first if necessary
 - Don't read from timerFd when processing expiry event

Result

- Cleaner API for integrating with different EL/queue timing impls
- Fixed race condition to avoid missing scheduled wakeups
- Eliminate unnecessary timerFd updates while EL is awake, and
unnecessary expired timerFd reads
- Avoid unnecessary scheduled-task wakeups when using NIO transport

I did not yet further explore the suggestion of using
TFD_TIMER_ABSTIME for the timerFd.
2019-08-21 12:34:22 +02:00
lwlee2608
cb739b2619 Update javadoc for NioEventLoop.setRatio() #9481 (#9484)
Motivation:

Improve java apidoc for NioEventLoop.setRatio

Modification:

javadoc

Result:

Fixes #9481
2019-08-21 09:13:42 +02:00
Norman Maurer
97361fa2c8
Replace synchronized usage with ConcurrentHashMap in *Bootstrap classes (#9458)
Motivation:

In AbstractBoostrap, options and attrs are LinkedHashMap that are synchronized on for every read, copy/clone, write operation.
When a lot of connections are triggered concurrently on the same bootstrap instance, the synchronized blocks lead to contention, Netty IO threads get blocked, and performance may be severely degraded.

Modifications:

Use ConcurrentHashMap

Result:

Less contention. Fixes https://github.com/netty/netty/issues/9426
2019-08-16 15:18:17 +02:00
Scott Mitchell
1fa7a5e697 EPOLL - decouple schedule tasks from epoll_wait life cycle (#7834)
Motivation:
EPOLL supports decoupling the timed wakeup mechanism from the selector call. The EPOLL transport takes advantage of this in order to offer more fine grained timer resolution. However we are current calling timerfd_settime on each call to epoll_wait and this is expensive. We don't have to re-arm the timer on every call to epoll_wait and instead only have to arm the timer when a task is scheduled with an earlier expiration than any other existing scheduled task.

Modifications:
- Before scheduled tasks are added to the task queue, we determine if the new
  duration is the soonest to expire, and if so update with timerfd_settime. We
also drain all the tasks at the end of the event loop to make sure we service
any expired tasks and get an accurate next time delay.
- EpollEventLoop maintains a volatile variable which represents the next deadline to expire. This variable is modified inside the event loop thread (before calling epoll_wait) and out side the event loop thread (immediately to ensure proper wakeup time).
- Execute the task queue before the schedule task priority queue. This means we
  may delay the processing of scheduled tasks but it ensures we transfer all
pending tasks from the task queue to the scheduled priority queue to run the
soonest to expire scheduled task first.
- Deprecate IORatio on EpollEventLoop, and drain the executor and scheduled queue on each event loop wakeup. Coupling the amount of time we are allowed to drain the executor queue to a proportion of time we process inbound IO may lead to unbounded queue sizes and unpredictable latency.

Result:
Fixes https://github.com/netty/netty/issues/7829
- In most cases this results in less calls to timerfd_settime
- Less event loop wakeups just to check for scheduled tasks executed outside the event loop
- More predictable executor queue and scheduled task queue draining
- More accurate and responsive scheduled task execution
2019-08-14 10:11:04 +02:00