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:
See https://github.com/netty/netty/issues/3411.
Backport perf improvements on 4.0 and make AsyncHttpClient DNS modules
backports easier to maintain.
Modifications:
Cherry-picked b7415a3307
Result:
Reuse a thread local ArrayList to avoid allocations.
Motivation:
The current slow path of FastThreadLocal is much slower than JDK ThreadLocal. See #4418
Modifications:
- Add FastThreadLocalSlowPathBenchmark for the flow path of FastThreadLocal
- Add final to speed up the slow path of FastThreadLocal
Result:
The slow path of FastThreadLocal is improved.
Motivation:
We want to allow the use of an uber jar that contains shared dynamic libraries for all platforms (including fedora).
Modifications:
Modified OpenSsl to try and load the fedora library if the OS is Linux and the platform specified library fails before using the default lib.
Result:
True uber support.
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:
A custom SecurityManager may prevent calling File.exists() and so throw a SecurityException in the static init block of NetUtil.
Modifications:
Correctly catch the exception and so allow to static init NetUtil.
Result:
Allow static init method of NetUtil to work even with custom SecurityManager.
Motivation:
See #3321
Modifications:
1. Add CharsetUtil.encoder/decoder() methods
2. Deprecate CharsetUtil.getEncoder/getDecoder() methods
Result:
Users can use new CharsetUtil.encoder/decoder() to specify error actions
Motivation:
See #3746.
Modifications:
Fork SpscLinkedQueue and SpscLinkedAtomicQueue from JCTools based on 7846450e28
Result:
Add SpscLinkedQueue and SpscLinkedAtomicQueue and apply it in LocalChannel.
Motivation:
If the Future that the PromiseNotifier is listening to is cancelled, it does not propagate the cancel to all the promises it is expected to notify.
Modifications:
- If the future is cancelled then all the promises should be cancelled
- Add a UnaryPromiseNotifier if a collection of promises is not necessary
Result:
PromiseNotifier propagates cancel events to all promises
Motivation:
ResourceLeakDetector enforces a limit as to how large the queue is allowed to grow for stack traces in order to keep memory from growing too large. However it is not always clear when records are dropped, or how many have been dropped. This can make interpreting leak reports more difficult if you assume all information is present when it may not be. Also we should increase the limit (currently 4) when running tests on the CI servers.
Modifications:
- Increase leak detector record limit on CI servers from 4 to 32.
- Track how many records have been discarded and disclose this in the leak report.
Result:
Leak reports clarify how many records were dropped, and how to increase the limit.
Motivation:
PlatformDependent allows some exceptions to escape during static initialization. If an exception escapes it will be translated into a java.lang.ExceptionInInitializerError and render the application unable to run.
Modifications:
- Make sure to catch Throwable during static initialization.
Result:
PlatformDependent static initialization doesn't result in java.lang.ExceptionInInitializerError.
Motivation:
* newAtomicIntegerFieldUpdater and newAtomicLongFieldUpdater take a
class<?> so they're too lax
* newAtomicReferenceFieldUpdater takes a Class<U> so it's too strict
and can only be passe a rawtype parameter when dealing w/ generic
classes
Modifications:
Take a Class<? super T> parameter instead.
Result:
Better type safety and generics support.
Motivation:
DomainNameMapping.add() makes DomainNameMapping look like it's safe to call add() anytime, and this is never true. It's probably better deprecate add() and introduce DomainNameMappingBuilder.
Modifications:
Made an immutable implementation of DomainNameMapping;
Added Builder for immutable DomainNameMapping;
Replaced regex pattern with String::startsWith check;
Replaced HashMap with two arrays in ImmutableDomainNameMapping;
Deprecated mutable API;
Estimation for StringBuilder initial size in ImmutableDomainNameMapping#toString()
Added StringUtil#commonSuffixOfLength
Replaced unnecessary substrings creation in DomainNameMapping#matches with regionMatches
Result:
Clients will be able to create immutable instances of DomainNameMapping with builder API.
Motivation:
UTF-16 can not represent the full range of Unicode characters, and thus has the concept of Surrogate Pair (http://unicode.org/glossary/#surrogate_pair) where 2 16-bit code units can be used to represent the missing characters. ByteBufUtil.writeUtf8 is currently does not support this and is thus incomplete.
Modifications:
- Add support for surrogate pairs in ByteBufUtil.writeUtf8
Result:
ByteBufUtil.writeUtf8 now supports surrogate pairs and is correctly converting to UTF-8.
Motivation:
DefaultPromiseTest has dead code which was left over from a code restructure. Shared code between 2 tests was moved into a common method, but some code which was not cleaned up in each of these methods after the code was moved.
Modifications:
- Delete dead code in DefaultPromiseTest
Result:
Less dead code
Motivation:
AbstractFuture currently wraps CancellationException in a ExecutionException. However the interface of Future says that this exception should be directly thrown.
Modifications:
- Throw CancellationException from AbstractFuture.get
Result:
Interface contract for CancellationException is honored in AbstractFuture.
Motivation:
There is a notification ordering issue in DefaultPromise when the lateListener collection is in use. The ordering issue can be observed in situations where a late listener is added to a Future returned from a write operation. It is possible that this future will run after a read operation scheduled on the I/O thread, even if the late listener is added on the I/O thread. This can lead to unexpected ordering where a listener for a write operation which must complete in order for the read operation to happen is notified after the read operation is done.
Modifications:
- If the lateListener collection becomes empty, it should be treated as though it was null when checking if lateListeners can be notified immediatley (instead of executing a task on the executor)
Result:
Ordering is more natural and will not be perceived as being out of order relative to other tasks on the same executor.
Motivation:
If netty used as part of application, should be a way to prefix service thread name to easy distinguish such threads (for example, used in IntelliJ Platform)
Modifications:
Introduce system property io.netty.serviceThreadPrefix
Result:
ThreadDeathWatcher thread has a readable name "Netty threadDeathWatcher-2-1" if io.netty.serviceThreadPrefix set to "Netty"
Motivation:
In 4.1 and master the isValid utility has been moved to MathUtil. We should stay consistent for internal APIs.
Modifications:
- Move isValid to MathUtil
Result:
More consistent internal structure across branches.
Motivation:
DefaultPromise.toString() returns 'DefaultPromise(incomplete)' when it's
actually complete with non-null result.
Modifications:
Handle the case where the promise is done and its result is non-null in
toString()
Result:
The String returned by DefaultPromise.toString() is not confusing
anymore.
Motivation:
Modulo operations are slow, we can use bitwise operation to detect if resource leak detection must be done while sampling.
Modifications:
- Ensure the interval is a power of two
- Use bitwise operation for sampling
- Add benchmark.
Result:
Faster sampling.
Motivation:
When the ImmediateEventExecutor is in use it is possible to get a StackOverFlowException if when a promise completes a new listener is added to that promise.
Modifications:
- Protect against the case where LateListeners.run() smashes the stack.
Result:
Fixes https://github.com/netty/netty/issues/4395
Motivation:
sun.misc.Unsafe allows us to handle heap ByteBuf in a more efficient matter. We should use special ByteBuf implementation when sun.misc.Unsafe can be used to increase performance.
Modifications:
- Add PooledUnsafeHeapByteBuf and UnpooledUnsafeHeapByteBuf that are used when sun.misc.Unsafe is ready to use.
- Add UnsafeHeapSwappedByteBuf
Result:
Better performance when using heap buffers and sun.misc.Unsafe is ready to use.
Motivation:
We had a bug in our implemention which double "reversed" bytes on systems which not support unaligned access.
Modifications:
- Correctly only reverse bytes if needed.
- Share code between unsafe implementations.
Result:
No more data-corruption on sytems without unaligned access.
Motivation:
We started the thread before store it in a field which could lead to an assert error when the thread is executed before we actually store it.
Modifications:
Store thread before start it.
Result:
No more assert error possible.
Motivation:
At the moment we only forward decoded messages that were added the out List once the full decode loop was completed. This has the affect that resources may not be released as fast as possible and as an application may incounter higher latency if the user triggeres a writeAndFlush(...) as a result of the decoded messages.
Modifications:
- forward decoded messages after each decode call
Result:
Forwarding decoded messages through the pipeline in a more eager fashion.
Motivation:
Leak detector, when it detects a leak, will print the last 5 stack
traces that touched the ByteBuf. In some cases that might not be enough
to identify the root cause of the leak.
Also, sometimes users might not be interested in tracing all the
operations on the buffer, but just the ones that are affecting the
reference count.
Modifications:
Added command line properties to override default values:
* Allow to configure max number of stack traces to collect
* Allow to only record retain/release operation on buffers
Result:
Users can increase the number of stack traces to debug buffer leaks
with lot of retain/release operations.
Motivation:
for debugging and metrics reasons its sometimes useful to be able to get details of the the Thread that powers a SingleThreadEventExecutor.
Modifications:
- Expose ThreadProperties
- Add unit test.
Result:
It's now possible to get details of the Thread that powers a SingleThreadEventExecutor.
Motivation:
Sometimes it is useful to disable recycling completely if memory constraints are very tight.
Modifications:
Allow to use -Dio.netty.recycler.maxCapacity.default=0 to disable recycling completely.
Result:
It's possible to disable recycling now.
Motivation:
The javadocs are incorrect and so give false impressions of use-pattern.
Modifications:
- Fix javadocs of which operations are allowed from multiple threads concurrently.
- Let isEmpty() work concurrently.
Result:
Correctly document usage-patterns.
Motivation:
The StringUtil class creates a Formatter object, but does not close it. There are also a 2 utility methods which would be generally useful.
Modifications:
- Close the Formatter
- Add length and isNullOrEmpty
Result:
No more resource leaks. Additional utility methods.
Motivation:
The HttpObjectDecoder is on the hot code path for the http codec. There are a few hot methods which can be modified to improve performance.
Modifications:
- Modify AppendableCharSequence to provide unsafe methods which don't need to re-check bounds for every call.
- Update HttpObjectDecoder methods to take advantage of new AppendableCharSequence methods.
Result:
Peformance boost for decoding http objects.
Motivation:
Prior we used a purge task that would remove previous canceled scheduled tasks from the internal queue. This could introduce some delay and so use a lot of memory even if the task itself is already canceled.
Modifications:
Schedule removal of task from queue via EventLoop if cancel operation is not done in the EventLoop Thread or just remove directly if the Thread that cancels the scheduled task is in the EventLoop.
Result:
Faster possibility to GC a canceled ScheduledFutureTask.
