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.
Motivation
Currently an epoll_ctl syscall is made every time there is a change to
the event interest flags (EPOLLIN, EPOLLOUT, etc) of a channel. These
are only done in the event loop so can be aggregated into 0 or 1 such
calls per channel prior to the next call to epoll_wait.
Modifications
I think further streamlining/simplification is possible but for now I've
tried to minimize structural changes and added the aggregation beneath
the existing flag manipulation logic.
A new AbstractChannel#activeFlags field records the flags last set on
the epoll fd for that channel. Calls to setFlag/clearFlag update the
flags field as before but instead of calling epoll_ctl immediately, just
set or clear a bit for the channel in a new bitset in the associated
EpollEventLoop to reflect whether there's any change to the last set
value.
Prior to calling epoll_wait the event loop makes the appropriate
epoll_ctl(EPOLL_CTL_MOD) call once for each channel who's bit is set.
Result
Fewer syscalls, particularly in some auto-read=false cases. Simplified
error handling from centralization of these calls.
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
Motivation:
EpollDatagramChannel#localAddress returns wrong information when
EpollDatagramChannel is created with InternetProtocolFamily,
and EpollDatagramChannel#localAddress is invoked BEFORE the actual binding.
This is a regression caused by change
e17ce934da
Modifications:
EpollDatagramChannel() and EpollDatagramChannel(InternetProtocolFamily family)
do not cache local/remote address
Result:
Rebinding on the same address without "reuse port" works
EpollDatagramChannel#localAddress returns correct address
Motivation:
On openSUSE (probably more), 64 bit builds use lib64, e.g. /usr/lib64, and
configure picks this up and builds the native library in
native-build/target/lib64 where maven is not looking.
Modifications:
Explicitly specify --libdir=${project.build.directory}/native-build/target/lib
during configuration.
Result:
Maven uses the correct lib directory.
Motivation:
We recently made a change to use ET for the eventfd and not trigger a read each time. This testcase proves everything works as expected.
Modifications:
Add testcase that verifies thqat the wakeups happen correctly
Result:
More tests
Motivation
The AbstractEpollStreamChannel::spliceTo(FileDescriptor, ...) methods
take an offset parameter but this was effectively ignored due to what
looks like a typo in the corresponding JNI function impl. Instead it
would always use the file's own native offset.
Modification
- Fix typo in netty_epoll_native_splice0() and offset accounting in
AbstractEpollStreamChannel::SpliceFdTask.
- Modify unit test to include an invocation of the public spliceTo
method using non-zero offset.
Result
spliceTo FD methods work as expected when an offset is provided.
Motivation
I noticed this while looking at something else.
AbstractEpollStreamChannel::spliceQueue is an MPSC queue but only
accessed from the event loop. So it could be just changed to e.g. an
ArrayDeque. This PR instead reverts to using is as an MPSC queue to
avoid dispatching a task to the EL, as appears was the original
intention.
Modification
Change AbstractEpollStreamChannel::spliceQueue to be volatile and lazily
initialized via double-checked locking. Add tasks directly to the queue
from the public methods rather than possibly waking the EL just to
enqueue.
An alternative is just to change PlatformDependent.newMpscQueue() to new
ArrayDeque() and be done with it :)
Result
Less disruptive channel/fd-splicing.
Motivation:
Netty homepage(netty.io) serves both "http" and "https".
It's recommended to use https than http.
Modification:
I changed from "http://netty.io" to "https://netty.io"
Result:
No effects.
Motivation:
Compiling with -Werror,-Wuninitialized complains about the sockaddrs being uninitialized.
I believe this is because the init function netty_unix_socket_initSockaddr is in a
separate compilation unit. Since this code isn't on the criticial path, it's easy
to just memset the variables rather than suppress the warning.
Modification:
Always clear the sockaddrs, even if they will be initialized later.
Result:
Able to compile with warnings turned on
Motivation:
Some methods that either override others or are implemented as part of implementation an interface did miss the `@Override` annotation
Modifications:
Add missing `@Override`s
Result:
Code cleanup
Motivation:
c9aaa93d83 added the ability to specify an EventLoopTaskQueueFactory but did place it under MultithreadEventLoopGroup while not really belongs there.
Modifications:
Make EventLoopTaskQueueFactory a top-level interface
Result:
More logical code layout.
Motivation:
Sometimes it is desirable to be able to use a different Queue implementation for the EventLoop of a Channel. This is currently not possible without resort to reflection.
Modifications:
- Add a new constructor to Nio|Epoll|KQueueEventLoopGroup which allows to specify a factory which is used to create the task queue. This was the user can override the default implementation.
- Add test
Result:
Be able to change Queue that is used for the EventLoop.
Motivation:
We did not have support for enable / disable loopback mode in our native epoll transport and also missed the implemention to access the configured interface.
Modifications:
Add implementation and adjust test to cover it
Result:
More complete multicast support with native epoll transport
Motivation:
The wakeup logic in EpollEventLoop is overly complex
Modification:
* Simplify the race to wakeup the loop
* Dont let the event loop wake up itself (it's already awake!)
* Make event loop check if there are any more tasks after preparing to
sleep. There is small window where the non-eventloop writers can issue
eventfd writes here, but that is okay.
Result:
Cleaner wakeup logic.
Benchmarks:
```
BEFORE
Benchmark Mode Cnt Score Error Units
EpollSocketChannelBenchmark.executeMulti thrpt 20 408381.411 ± 2857.498 ops/s
EpollSocketChannelBenchmark.executeSingle thrpt 20 157022.360 ± 1240.573 ops/s
EpollSocketChannelBenchmark.pingPong thrpt 20 60571.704 ± 331.125 ops/s
Benchmark Mode Cnt Score Error Units
EpollSocketChannelBenchmark.executeMulti thrpt 20 440546.953 ± 1652.823 ops/s
EpollSocketChannelBenchmark.executeSingle thrpt 20 168114.751 ± 1176.609 ops/s
EpollSocketChannelBenchmark.pingPong thrpt 20 61231.878 ± 520.108 ops/s
```
Motivation:
We do not need to issue a read on timerfd and eventfd when the EventLoop wakes up if we register these as Edge-Triggered. This removes the overhead of 2 syscalls and so helps to reduce latency.
Modifications:
- Ensure we register the timerfd and eventfd with EPOLLET flag
- If eventfd_write fails with EAGAIN, call eventfd_read and try eventfd_write again as we only use it as wake-up mechanism.
Result:
Less syscalls and so reducing overhead.
Co-authored-by: Carl Mastrangelo <carl@carlmastrangelo.com>
Motivation:
When EpollDatagramChannel is created with an existing FileDescriptor we should detect the correct InternetProtocolFamily.
Modifications:
Obtain the InternetProtocolFamily from the given FD
Result:
Use correct InternetProtocolFamily when EpollDatagramChannel is created via existing FileDescriptor
Motivation:
Provide epoll/native multicast to support high load multicast users (we are using it for a high load telecomm app at my day job).
Modification:
Added support for source specific and any source multicast for epoll transport. Some caveats: no support for disabling loop back mode, retrieval of interface and block operation, all of which tend to be less frequently used.
Result:
Provides epoll transport multicast for common use cases.
Co-authored-by: Norman Maurer <norman_maurer@apple.com>
Motivation:
The current KQueueEventLoop implementation does not process concurrent domain socket channel registration/unregistration in the order they actual
happen since unregistration are delated by an event loop task scheduling. When a domain socket is closed, it's file descriptor might be reused
quickly and therefore trigger a new channel registration using the same descriptor.
Consequently the KQueueEventLoop#add(AbstractKQueueChannel) method will overwrite the current inactive channels having the same descriptor
and the delayed KQueueEventLoop#remove(AbstractKQueueChannel) will remove the active channel that replaced the inactive one.
As active channels are registered, events for this file descriptor won't be processed anymore and the channels will never be closed.
The same problem can also happen in EpollEventLoop. Beside this we also may never remove the AbstractEpollChannel from the internal map
when it is unregistered which will prevent it from be GC'ed
Modifications:
- Change logic of native KQueue and Epoll implementations to ensure we correctly handle the case of FD reuse
- Only try to update kevent / epoll if the Channel is still open (as otherwise it will be handled by kqueue / epoll itself)
- Correctly remove AbstractEpollChannel from internal map in all cases
- Make implementation of closeAll() consistent for Epoll and KQueueEventLoop
Result:
KQueue and Epoll native transports correctly handle FD reuse
Co-authored-by: Norman Maurer <norman_maurer@apple.com>
Motivation:
OOME is occurred by increasing suppressedExceptions because other libraries call Throwable#addSuppressed. As we have no control over what other libraries do we need to ensure this can not lead to OOME.
Modifications:
Only use static instances of the Exceptions if we can either dissable addSuppressed or we run on java6.
Result:
Not possible to OOME because of addSuppressed. Fixes https://github.com/netty/netty/issues/9151.
Motivation
These aren't needed, only one field from each class is used. It also showed as an ambiguous identifier compilation error in my IDE even though javac is obviously fine with it.
Modifications
Static-import explicit ChannelOption fields in EpollDomainSocketChannelConfig instead of using .* wildcard.
Result
Cleaner / more consistent code.
Motivation
These implementations delegate most of their methods to an existing Handle and previously extended RecvByteBufAllocator.DelegatingHandle. This was reverted in #6322 with the introduction of ExtendedHandle but it's not clear to me why it needed to be - the code looks a lot cleaner.
Modifications
Have (Epoll|KQueue)RecvByteAllocatorHandle extend DelegatingHandle again, while still implementing ExtendedHandle.
Result
Less code.
Motivation:
At the moment we throw a ChannelException if netty_epoll_linuxsocket_setTcpMd5Sig fails. This is inconsistent with other methods which throw a IOException.
Modifications:
Throw IOException
Result:
More correct and consistent exception usage in epoll transport
Motivation:
We currently only cover ipv4 multicast in the testsuite but we should also have tests for ipv6.
Modifications:
- Add test for ipv6
- Ensure we only try to run multicast test for ipv4 / ipv6 if the loopback interface supports it.
Result:
Better test coverage
Motivation:
When netty_epoll_linuxsocket_setTcpMd5Sig fails to init the sockaddr we should throw an exception and not silently return.
Modifications:
Throw exception if init of sockaddr fails.
Result:
Correctly report back error to user.
…nterface, block or loopback-mode-disabled operations).
Motivation:
Provide epoll/native multicast to support high load multicast users (we are using it for a high load telecomm app at my day job).
Modification:
Added support for (ipv4 only) source specific and any source multicast for epoll transport. Some caveats (beyond no ipv6 support initially - there’s a bit of work to add in join and leave group specifically around SSM, as ipv6 uses different data structures for this): no support for disabling loop back mode, retrieval of interface and block operation, all of which tend to be less frequently used.
Result:
Provides epoll transport multicast for IPv4 for common use cases. Understand if you’d prefer to hold off until ipv6 is included but not sure when I’ll be able to get to that.
Motivation:
Systems depending on Netty may benefit (telemetry, alternative even loop scheduling algorithms) from knowing the number of channels assigned to each EventLoop.
Modification:
Expose the number of channels registered in the EventLoop via SingleThreadEventLoop.registeredChannels.
Result:
Fixes#8276.
Motivation:
com.puppycrawl.tools checkstyle < 8.18 was reported to contain a possible security flaw. We should upgrade.
Modifications:
- Upgrade netty-build and checkstyle.
- Fix checkstyle errors
Result:
Fixes https://github.com/netty/netty/issues/8968.
Motivation:
Since DomainSocketChannel is a DuplexChannel, which be able to shutdown input or output individually on demands, but ALLOW_HALF_CLOSURE channel option has not been supported yet.
I thought this could be a missing feature of Unix domain socket, so here the PR for it.
Modifications:
1. Added allHalfClosure property both in EpollDomainSocketChannelConfig and KQueueDomainSocketChannelConfig,
2. Enabled isAllowHalfClosure method of native channel to support domain channel config,
3. Created EpollDomainSocketShutdownOutputByPeerTest and KQueueDomainSocketShutdownOutputByPeerTest to verify the change.
Result:
ALLOW_HALF_CLOSURE channel option can be set with DomainSocketChannel, and no more warning of Unknown channel option 'ALLOW_HALF_CLOSURE'.
Motivation:
At some point we needed --add-opens=java.base/java.nio=ALL-UNNAMED to run our native tests but this is not true anymore.
Modifications:
Remove --add-opens=java.base/java.nio=ALL-UNNAMED when running native tests.
Result:
Remove obsolate jvm arg.
Motivation:
`DefaultFileRegion.transferTo` will return 0 all the time when we request more data then the actual file size. This may result in a busy spin while processing the fileregion during writes.
Modifications:
- If we wrote 0 bytes check if the underlying file size is smaller then the requested count and if so throw an IOException
- Add DefaultFileRegionTest
- Add a test to the testsuite
Result:
Fixes https://github.com/netty/netty/issues/8868.
Motivation:
The SSLEngine does provide a way to signal to the caller that it may need to execute a blocking / long-running task which then can be offloaded to an Executor to ensure the I/O thread is not blocked. Currently how we handle this in SslHandler is not really optimal as while we offload to the Executor we still block the I/O Thread.
Modifications:
- Correctly support offloading the task to the Executor while suspending processing of SSL in the I/O Thread
- Add new methods to SslContext to specify the Executor when creating a SslHandler
- Remove @deprecated annotations from SslHandler constructor that takes an Executor
- Adjust tests to also run with the Executor to ensure all works as expected.
Result:
Be able to offload long running tasks to an Executor when using SslHandler. Partly fixes https://github.com/netty/netty/issues/7862 and https://github.com/netty/netty/issues/7020.
Motivation:
We missed to extend a few tests from the testsuite and so also run these with our native KQueue and Epoll transport.
Modifications:
Extend tests and so run these for our native transports as well.
Result:
More tests.
Motivation:
When using a linux distribution that supports sendmmsg(...) we allocated enough direct memory per EpollEventLoop to be able to write IOV_MAX number of iovecs per message that can be written per sendmmsg.
The number of messages that can be written per sendmmsg(...) call is limited by UIO_MAX_IOV.
In practice this resulted in an allocation of 16MB direct memory per EpollEventLoop instance that stayed allocated until the EpollEventLoop was shutdown which happens as part of the shutdown of the enclosing EpollEVentLoopGroup.
This resulted in quite some heavy direct memory usage in practice even when in practice we have very slim changes to ever need all of the memory.
Modification:
Adjust NativeDatagramPacketArray to share one IovArray instance across all NativeDatagramPacket instances it holds. This limits the max number of iovecs we can write across all messages to IOV_MAX per sendmmsg(...) call.
This in practice will still be enough to allow us to write multiple messages with one syscall while keep the memory overhead to a minimum.
Result:
Smaller direct memory footprint per EpollEventLoop when using EpollDatagramChannel on distributions that support sendmmsg(...).
Fixes https://github.com/netty/netty/issues/8814
Motivation:
In the native code EpollDatagramChannel / KQueueDatagramChannel creates a DatagramSocketAddress object for each received UDP datagram even when in connected mode as it uses the recvfrom(...) / recvmsg(...) method. Creating these is quite heavy in terms of allocations as internally, char[], String, Inet4Address, InetAddressHolder, InetSocketAddressHolder, InetAddress[], byte[] objects are getting generated when constructing the object. When in connected mode we can just use regular read(...) calls which do not need to allocate all of these.
Modifications:
- When in connected mode use read(...) and NOT recvfrom(..) / readmsg(...) to reduce allocations when possible.
- Adjust tests to ensure read works as expected when in connected mode.
Result:
Less allocations and GC when using native datagram channels in connected mode. Fixes https://github.com/netty/netty/issues/8770.
Motivation:
We have a utility method to check for > 0 and >0 arguments. We should use it.
Modification:
use checkPositive/checkPositiveOrZero instead of if statement.
Result:
Re-use utility method.
