Motivation:
`FormattingTuple.getArgArray()` is never used.
In the `MessageFormatter` it is possible to make
some improvements, e.g. replace `StringBuffer`
with `StringBuilder`, avoid redundant allocations, etc.
Modifications:
- Remove `argArray` field from the `FormattingTuple`.
- In `MessageFormatter`:
- replace `StringBuffer` with `StringBuilder`,
- replace `HashMap` with `HashSet` and make it lazy initialized.
- avoid redundant allocations (`substring()`, etc.)
- use appropriate StringBuilder's methods for the some `Number` values.
- Porting unit tests from `slf4j`.
Result:
Less GC load on logging with internal `MessageFormatter`.
Motivation:
IPv4/6 validation methods use allocations, which can be avoided.
IPv4 parse method use StringTokenizer.
Modifications:
Rewriting IPv4/6 validation methods to avoid allocations.
Rewriting IPv4 parse method without use StringTokenizer.
Result:
IPv4/6 validation and IPv4 parsing faster up to 2-10x.
Motivation:
We should only try to load jdk.internal.misc.Unsafe if we run on Java9+ to eliminate noise in the log.
Modifications:
- Move javaVersion() and related methods to PlatformDependent0 to be able to use these in the static initializer without creating a cycle.
- Only try to load jdk.internal.misc.Unsafe when running in Java9+
Result:
Less noise in the log when running pre java9.
Motivation:
A previous change allocated a new thread local string builder if it
was getting too large. This is a good change, these string builders
can accidentally get too large and then never shrunk and that is sort
of a memory leak. However, the change allocates an entirely new string
builder which is more allocations than necessary. Instead, we can trim
the string builder if its too large, this only allocates an extra
backing array instead of a whole new object.
Modifications:
If the string builder is above a threshold, we trim the string builder
and then ensure its capacity is reasonable to we do not allocate too
much as we start using the string builder.
Result:
The thread local string builder do not serve as a memory yet we do not
allocate too many new objects.
Motivation:
`NetUtil`'s methods `isValidIpV6Address` and `getIPv6ByName` incorrectly validate some IPv6 addresses.
Modifications:
- `getIPv6ByName`: add checks for single colon at the start or end.
- `isValidIpV6Address`: fix checks for the count of colons and use `endOffset` instead of `ipAddress.length()` for the cases with the brackets or '%'.
Result:
More correct implementation of `NetUtil#isValidIpV6Address` and `NetUtil#getIPv6ByName`.
Motivation:
AtomicIntegerFieldUpdater#get is unnecessary, I think use simple volatile read is cleaner
Modifications:
Replace code STATE_UPDATER.get(this) to state in SingleThreadEventExecutor
Result:
Cleaner code
Motivation:
InternalThreadLocalMap#stringBuilder: ensure memory overhead
Modification:
If the capacity of StringBuilder is greater than 65536 then release it on the next time you get StringBuilder and re-create a StringBuilder.
Result:
Possible less memory usage.
Motivation:
If unsafe is unavailable, we can not use the cleaner anyway. If we try
to set it up, we get an annoying log message about unsafe being
unavailable (when debug logging is enabled). We know this will fail, so
we should not even bother and avoid the log message.
Modifications:
This commit adds a guard against setting up the cleaner if it is not
going to be available because unsafe is unavailable.
Result:
We do not try to set up the cleaner if unsafe is unavailable, and we do
not get an annoying log message.
Motivation:
Users should not see a scary log message when Netty is initialized if
Netty configuration explicitly disables unsafe. The log message that
produces this warning was previously guarded but the guard was
lost.
Modifications:
This commit brings back the guard against the scary log message if
unsafe is explicitly disabled.
Result:
No log message is produced when unsafe is unavailable because Netty was
told to not look for it.
Motivation:
We currently don't have a native transport which supports kqueue https://www.freebsd.org/cgi/man.cgi?query=kqueue&sektion=2. This can be useful for BSD systems such as MacOS to take advantage of native features, and provide feature parity with the Linux native transport.
Modifications:
- Make a new transport-native-unix-common module with all the java classes and JNI code for generic unix items. This module will build a static library for each unix platform, and included in the dynamic libraries used for JNI (e.g. transport-native-epoll, and eventually kqueue).
- Make a new transport-native-unix-common-tests module where the tests for the transport-native-unix-common module will live. This is so each unix platform can inherit from these test and ensure they pass.
- Add a new transport-native-kqueue module which uses JNI to directly interact with kqueue
Result:
JNI support for kqueue.
Fixes https://github.com/netty/netty/issues/2448
Fixes https://github.com/netty/netty/issues/4231
Motivation:
Fixes#6681.
Modification:
For the sake of better timer observability, expose the number of pending timeouts through the new HashedWheelTimer.pendingTimeouts method .
Result:
It's now ridiculously easy to observe Netty timer's very basic and yet important metric, the number of pending tasks/timeouts.
Motivation:
NetUtil#isValidIpV6Address and NetUtil#getIPv6ByName allowed an invalid form of mapped IPv4 addresses which lead to accepting invalid IPv6 addresses as valid.
Modifications:
- NetUtil#isValidIpV6Address and NetUtil#getIPv6ByName should only allow 7 colons for an IPv4 address if they are the first 2 characters.
Result:
More correct implementation of NetUtil#isValidIpV6Address and NetUtil#getIPv6ByName
Motivation:
NetUtil#getByName and NetUtil#isValidIpV6Address do not strictly enforce the format of IPv4 addresses that are allowed to be embedded in IPv6 addresses as specified in https://tools.ietf.org/html/rfc4291#section-2.5.5. This may lead to invalid addresses being parsed, or invalid addresses being considered valid. Compression of a single IPv6 word was also not handled correctly if there are 7 : characters.
Modifications:
- NetUtil#isValidIpV6Address should enforce the IPv4-Compatible and IPv4-Mapped are the only valid formats for including IPv4 addresses as specified in https://tools.ietf.org/html/rfc4291#section-2.5.5
- NetUtil#getByName should more stritcly parse IPv6 addresses which contain IPv4 addresses as specified in https://tools.ietf.org/html/rfc4291#section-2.5.5
- NetUtil should allow compression even if the number of : characters is 7.
- NetUtil#createByteArrayFromIpAddressString should use the same IP string to byte[] translation which is used in NetUtil#getByName
Result:
NetUtil#getByName and NetUtil#isValidIpV6Address respect the IPv6 RFC which defines the valid formats for embedding IPv4 addresses.
Motivation:
In cases when an application is running in a container or is otherwise
constrained to the number of processors that it is using, the JVM
invocation Runtime#availableProcessors will not return the constrained
value but rather the number of processors available to the virtual
machine. Netty uses this number in sizing various resources.
Additionally, some applications will constrain the number of threads
that they are using independenly of the number of processors available
on the system. Thus, applications should have a way to globally
configure the number of processors.
Modifications:
Rather than invoking Runtime#availableProcessors, Netty should rely on a
method that enables configuration when the JVM is started or by the
application. This commit exposes a new class NettyRuntime for enabling
such configuraiton. This value can only be set once. Its default value
is Runtime#availableProcessors so that there is no visible change to
existing applications, but enables configuring either a system property
or configuring during application startup (e.g., based on settings used
to configure the application).
Additionally, we introduce the usage of forbidden-apis to prevent future
uses of Runtime#availableProcessors from creeping. Future work should
enable the bundled signatures and clean up uses of deprecated and
other forbidden methods.
Result:
Netty can be configured to not use the underlying number of processors,
but rather the constrained number of processors.
Motivation:
Java9 added a new method to Unsafe which allows to allocate a byte[] without memset it. This can have a massive impact in allocation times when the byte[] is big. This change allows to enable this when using Java9 with the io.netty.tryAllocateUninitializedArray property when running Java9+. Please note that you will need to open up the jdk.internal.misc package via '--add-opens java.base/jdk.internal.misc=ALL-UNNAMED' as well.
Modifications:
Allow to allocate byte[] without memset on Java9+
Result:
Better performance when allocate big heap buffers and using java9.
Motivation:
As the javadoc of ScheduledExecutorService state:
Zero and negative delays (but not periods) are also allowed in schedule methods,and are treated as requests for immediate execution.
Modifications:
- Correctly handle delay <= 0.
- Add unit tests.
Result:
Fixes [#6627].
Motivation:
When debugging netty memory leaks, it's sometimes helpful to
print the object's reference count.
Modifications:
Add `refCnt` methods to set of already exitsting helpers for ref coutned
objects.
Result:
Users will have utility to print object's ref count without much of a
boilerplate.
Motivation:
Java9 adds a new method to Unsafe which allows to free direct ByteBuffer via the cleaner without the need to use an commandline arguments.
Modifications:
- Add Cleaner interface
- Add CleanerJava9 which will be used when using Java9+ and take care of release direct ByteBuffer
- Let Cleaner0 implement Cleaner
Result:
Be able to free direct ByteBuffer on Java9+ again without any commandline arguments.
Motivation:
When UNSAFE.allocateMemory is returning an address whose high bit is set we currently throw an IllegalArgumentException. This is not correct as it may return a negative number on at least sparc.
Modifications:
- Allow to pass in negative memoryAddress
- Add unit tests
Result:
Correctly validate the memoryAddress and so also work on sparc as expected. Fixes [#6574].
Motivation:
The updated HTTP/1.x RFC allows for header values to be CSV and separated by OWS [1]. CombinedHttpHeaders should remove this OWS on insertion.
[1] https://tools.ietf.org/html/rfc7230#section-7
Modification:
CombinedHttpHeaders doesn't account for the OWS and returns it back to the user as part of the value.
Result:
Fixes#6452
Motivation:
We should use SystemPropertyUtil to access system properties and so always handle SecurityExceptions.
Modifications:
Use SystemPropertyUtil everywhere.
Result:
Better and consist handling of SecurityException.
Motivation:
We forked a new process to detect if the program is run by root. We should better just use user.name system property
Modifications:
- Change PlatformDependent.isRoot0() to read the user.name system property to detect if root runs the program and rename it to maybeSuperUser0().
- Rename PlatformDependent.isRoot() to maybeSuperUser() and let it init directly in the static block
Result:
Less heavy way to detect if the program is run by root.
Motivation:
When UnorderedThreadPoolEventExecutor.execute / submit etc is called it will consume up to 100 % CPU even after the task was executed.
Modifications:
Add a special wrapper which we will be used in execute(...) to wrap the submitted Runnable. This is needed as ScheduledThreadPoolExecutor.execute(...) will delegate to submit(...) which will then use decorateTask(...). The problem with this is that decorateTask(...) needs to ensure we only do our own decoration if we not call from execute(...) as otherwise we may end up creating an endless loop because DefaultPromise will call EventExecutor.execute(...) when notify the listeners of the promise.
Result:
Fixes [#6507].
Motivation:
PlatformDependent0 makes assumptions that the array index scale for byte[] is always 1. If this is not the case the results from methods which make this assumption will be undefined.
Modifications:
- PlatformDependent0 should check if unsafe.arrayIndexScale(byte[].class) is not 1, and if so not use unsafe
Result:
Assumptions made by optimizations in PlatformDependent0 which use byte[] are explicitly enforced.
Motivation:
We only need to add the port to the HOST header value if its not a standard port.
Modifications:
- Only add port if needed.
- Fix parsing of ipv6 address which is enclosed by [].
Result:
Fixes [#6426].
Motivation:
Calling a static method is faster then dynamic
Modifications:
Add 'static' keyword for methods where it missed
Result:
A bit faster method calls
Motivation:
We shipped a javassist based implementation for typematching and logged a confusing debug message about missing javassist. We never were able to prove it really gives any perf improvements so we should just remove it.
Modifications:
- Remove javassist dependency and impl
- Fix possible classloader deadlock as reported by intellij
Result:
Less code to maintain and less confusing log message.
Motivation:
We should log why we can not use ByteBuffer.cleaner and so maybe allow the user to fix it.
Modifications:
- Use Unsafe to access the field
- Log the exception when we can not use ByteBuffer.cleaner
Result:
Easier to debug why using cleaner is not possible.
Motivation:
We have our own ThreadLocalRandom implementation to support older JDKs . That said we should prefer the JDK provided when running on JDK >= 7
Modification:
Using ThreadLocalRandom implementation of the JDK when possible.
Result:
Make use of JDK implementations when possible.
Motivation:
Java9 does not allow changing access level via reflection by default. This lead to the situation that netty disabled Unsafe completely as ByteBuffer.address could not be read.
Modification:
Use Unsafe to read the address field as this works on all Java versions.
Result:
Again be able to use Unsafe optimisations when using Netty with Java9
Motivation:
NetworkInterface.getNetworkInterfaces() may return null if no network interfaces are found. We should guard against it.
Modifications:
Check for null return value.
Result:
Fixes [#6384]
Motiviation:
Simplify implementation of compareTo/equals/hashCode for ChannelIds.
Modifications:
We simplfy the hashCode implementation for DefaultChannelId by not
making it random, but making it based on the underlying data. We fix the
compareTo implementation for DefaultChannelId by using lexicographic
comparison of the underlying data array. We fix the compareTo
implementation for CustomChannelId to avoid the possibility of overflow.
Result:
Cleaner code that is easier to maintain.
Motivation:
Java8 is out now for some time and JDK7 is no longer supported officially. We should remove all our backports and just use what the JDK provides us. This also will allow us to use intrinsics that are offered by the JDK implementations.
Modifications:
Remove all backports of jdk8 classes.
Result:
Use what the JDK offers us. This also fixes [#5458]
Motivation:
Initialization of PlatformDependent0 fails on Java 9 in static initializer when calling setAccessible(true).
Modifications:
Add RefelectionUtil which can be used to safely try if setAccessible(true) can be used or not and if not fail back to non reflection.
Result:
Fixed [#6345]
Motivation:
EpollRecvByteAllocatorHandle intends to override the meaning of "maybe more data to read" which is a concept also used in all existing implementations of RecvByteBufAllocator$Handle but the interface doesn't support overriding. Because the interfaces lack the ability to propagate this computation EpollRecvByteAllocatorHandle attempts to implement a heuristic on top of the delegate which may lead to reading when we shouldn't or not reading data.
Modifications:
- Create a new interface ExtendedRecvByteBufAllocator and ExtendedHandle which allows the "maybe more data to read" between interfaces
- Deprecate RecvByteBufAllocator and change all existing implementations to extend ExtendedRecvByteBufAllocator
- transport-native-epoll should require ExtendedRecvByteBufAllocator so the "maybe more data to read" can be propagated to the ExtendedHandle
Result:
Fixes https://github.com/netty/netty/issues/6303.
Motivation:
The JDK uses gethostbyname for blocking hostname resoltuion. gethostbyname can be configured on Unix systems according to [1][2]. This may impact the name server that is used to resolve particular domains or just override the default fall-back resolver. DnsNameResolver currently ignores these configuration files which means the default resolution behavior is different than the JDK. This may lead to unexpected resolution failures which succeed when using the JDK's resolver.
Modifications:
- Add an interface which can override what DnsServerAddressStream to use for a given hostname
- Provide a Unix specific implementation of this interface and implement [1][2]. Some elements may be ignored sortlist, timeout, etc...
Result:
DnsNameResolver behaves more like the JDK resolver by default.
[1] https://linux.die.net/man/5/resolver
[2] https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html
Motivation:
ResourceLeakDetector supports a parameter called maxActive. This parameter is used in attempt to limit the amount of objects which are being tracked for leaks at any given time, and generates an error log message if this limit is exceeded. This assumes that there is a relationship between leak sample rate and object lifetime for objects which are already being tracked. This relationship may appear to work in cases were there are a single leak record per object and those leak records live for the lifetime of the application but in general this relationship doesn't exist. The original motivation was to provide a limit for cases such as HashedWheelTimer to limit the number of instances which exist at any given time. This limit is not enforced in all circumstances in HashedWheelTimer (e.g. if the thread is a daemon) and can be implemented outside ResourceLeakDetector.
Modifications:
- Deprecate all methods which interact with maxActive in ResourceLeakDetectorFactory and ResourceLeakDetector
- Remove all logic related to maxActive in ResourceLeakDetector
- HashedWheelTimer implements its own logic to impose a limit and warn users if too many instances exists at any given time.
Result:
Fixes https://github.com/netty/netty/issues/6225.
Motivation:
When comparing MAC addresses searching for the best MAC address, if
locally-administered address (e.g., from a Docker container) is compared
against an empty MAC address, the empty MAC address will be marked as
preferred. In cases this is the only available MAC address, this leaves
Netty using a random machine ID instead of using a perfectly valid
machine ID from the locally-adminstered address.
Modifications:
This commit modifies the MAC address logic so that the empty MAC address
is not preferred over a locally-administered address. This commit also
simplifies the comparison logic here.
Result:
Empty MAC addresses will not be preferred over locally-administered
addresses thus permitting the default machine ID to be the
locally-adminstered MAC address if it is the only available MAC address.
Motivation:
codec-http2 couples the dependency tree state with the remainder of the stream state (Http2Stream). This makes implementing constraints where stream state and dependency tree state diverge in the RFC challenging. For example the RFC recommends retaining dependency tree state after a stream transitions to closed [1]. Dependency tree state can be exchanged on streams in IDLE. In practice clients may use stream IDs for the purpose of establishing QoS classes and therefore retaining this dependency tree state can be important to client perceived performance. It is difficult to limit the total amount of state we retain when stream state and dependency tree state is combined.
Modifications:
- Remove dependency tree, priority, and weight related items from public facing Http2Connection and Http2Stream APIs. This information is optional to track and depends on the flow controller implementation.
- Move all dependency tree, priority, and weight related code from DefaultHttp2Connection to WeightedFairQueueByteDistributor. This is currently the only place which cares about priority. We can pull out the dependency tree related code in the future if it is generally useful to expose for other implementations.
- DefaultHttp2Connection should explicitly limit the number of reserved streams now that IDLE streams are no longer created.
Result:
More compliant with the HTTP/2 RFC.
Fixes https://github.com/netty/netty/issues/6206.
[1] https://tools.ietf.org/html/rfc7540#section-5.3.4
Motivation:
A testing goof in 7c630fe introduced a binary incompatibility when the old Promise-specific `add` and `addAll` methods in PromiseCombiner were generalized to accept `Futures`.
Modification:
- Restore (but mark as `@Deprecated`) old PromiseCombiner methods.
- Fixed a couple minor documentation typos because sure why not.
Result:
`PromiseCombiner` is binary-compatible with previous versions of Netty.
Motivation:
When an empty hostname is used in DnsNameResolver.resolve*(...) it will never notify the future / promise. The root cause is that we not correctly guard against errors of IDN.toASCII(...) which will throw an IllegalArgumentException when it can not parse its input. That said we should also handle an empty hostname the same way as the JDK does and just use "localhost" when this happens.
Modifications:
- If the try to resolve an empty hostname we use localhost
- Correctly guard against errors raised by IDN.toASCII(...) so we will always noify the future / promise
- Add unit test.
Result:
DnsNameResolver.resolve*(...) will always notify the future.
Motivation:
Currently Netty does not wrap socket connect, bind, or accept
operations in doPrivileged blocks. Nor does it wrap cases where a dns
lookup might happen.
This prevents an application utilizing the SecurityManager from
isolating SocketPermissions to Netty.
Modifications:
I have introduced a class (SocketUtils) that wraps operations
requiring SocketPermissions in doPrivileged blocks.
Result:
A user of Netty can grant SocketPermissions explicitly to the Netty
jar, without granting it to the rest of their application.
Motivation:
Replacing System.err during Slf4JLoggerFactory construction is problematic as another class may optain the System.err reference before we set it back to the original value.
Modifications:
Remove code that temporary replaced System.err.
Result:
Fixes [#6212].
Motivation:
Pattern matching not necessary for number parsing.
Modification:
Removed pattern matching for number parsing and removed unnecessary toLowerCase() operation.
Result:
No static variable with pattern, removed unnecessary matching operation and toLowerCase() operation.
Motivation:
PlatformDependent* contains some methods that are not used and some other things that can be cleaned-up.
Modifications:
- Remove unused methods
- cleanup
Result:
Code cleanup.
Motivation:
The HttpProxyHandler is expected to be capable of issuing a valid CONNECT request for a tunneled connection to an IPv6 host.
Modifications:
- Correctly format the IPV6 address.
- Add unit tests
Result:
HttpProxyHandler works with IPV6 as well. Fixes [#6152].
Motivation:
When DefaultHttp2Connection removes a stream it iterates over all children and adds them as children to the parent of the stream being removed. This process may remove elements from the child map while iterating without using the iterator's remove() method. This is generally unsafe and may result in an undefined iteration.
Modifications:
- We should use the Iterator's remove() method while iterating over the child map
Result:
Fixes https://github.com/netty/netty/issues/6163
Motivation:
[#6153] reports an endless loop that existed in the Recycler, while this was fixed adding a few asserts to ensure this remains fixed is a good thing. Beside this we also should ensure this can not escape the constructor to avoid unsafe publication.
Modifications:
- Add asserts
- Fix unsafe publication
Result:
More correct code.
Motivation:
`scavengeSome()` has a corner case: when setting `cursor` to `head`, `this.prev` may point to the tail of the `WeakOrderQueue` linked list. Then it's possible that the following while loop will link the tail to the head, and cause endless loop.
I made a reproducer in 36522e7b72 . The unit test will just run forever. Unfortunately, I cannot change it to a unit test because it needs to add some codes to `scavengeSome` to control the execution flow.
Modification:
Set `prev` to null when setting `cursor` to `head` in `scavengeSome`
Result:
Fixes#6153.
Motivation:
InternalThreadLocalMap.arrayList returns a new ArrayList every time it's called that defeats the purpose of having a reusable ArrayList.
Modification:
Modified InternalThreadLocalMap.arrayList to create an ArrayList only if arrayList field is NULL.
Result:
InternalThreadLocalMap.arrayList now creates a reusable ArrayList only if arrayList field is NULL.
Motivation:
We used a MPSC queue in ThreadDeathWatcher and checked if it empty via isEmpty() from multiple threads if very unlucky. Depending on the implementation this is not safe and may even produce things like live-locks.
Modifications:
Change to use a MPMC queue.
Result:
No more risk to run into issues when multiple threads call watch(...) / unwatch(...) concurrently.
Motivation:
DefaultChannelId provides a regular expression which validates if a user provided MAC address is valid. This regular expression may allow invalid MAC addresses and also not allow valid MAC addresses.
Modifications:
- Introduce a MacAddressUtil#parseMac method which can parse and validate the MAC address at the same time. The regular expression check before hand is additional overhead if we have to parse the MAC address.
Result:
Fixes https://github.com/netty/netty/issues/6132.
Motivation:
`PromiseCombiner` is really handy, but it's not obvious how to use it from its existing documentation/method signatures.
Modification:
- Added javadoc comments to explain the theory of operation of `PromiseCombiner`.
- Generalized `PromiseCombiner` to work with `Futures` so it's clearer that the things for which it's listening won't be modified.
Result:
`PromiseCombiner` is easier to understand.
Motivation:
When profiling it is sometimes needed to still have the native library file avaible. We should allow to disable the explicit deletion and just delete it when the JVM stops.
This is related to #6110
Modifications:
Add io.netty.native.deleteLibAfterLoading system property which allows to disable the explicit delete after laoding
Result:
Possible to profile native libraries better.
Motivation:
In later Java8 versions our Atomic*FieldUpdater are slower then the JDK implementations so we should not use ours anymore. Even worse the JDK implementations provide for example an optimized version of addAndGet(...) using intrinsics which makes it a lot faster for this use-case.
Modifications:
- Remove methods that return our own Atomic*FieldUpdaters.
- Use the JDK implementations everywhere.
Result:
Faster code.
Motivation:
InternalLoggerFactory either sets a default logger factory
implementation based on the logging implementations on the classpath, or
applications can set a logger factory explicitly. If applications wait
too long to set the logger factory, Netty will have already set a logger
factory leading to some objects using one logging implementation and
other objets using another logging implementation. This can happen too
if the application tries to set the logger factory twice, which is
likely a bug in the application. Yet, the Javadocs for
InternalLoggerFactory warn against this saying that
InternalLoggerFactory#setLoggerFactory "should be called as early as
possible and shouldn't be called more than once". Instead, Netty should
guard against this.
Modications:
We replace the logger factory field with an atomic reference on which we
can do CAS operations to safely guard against it being set twice. We
also add an internal holder class that captures the static interface of
InternalLoggerFactory that can aid in testing.
Result:
The logging factory can not be set twice, and applications that want to
set the logging factory must do it before any Netty classes are
initialized (or the default logger factory will be set).
Motivation:
We need to ensure the tracked object can not be GC'ed before ResourceLeak.close() is called as otherwise we may get false-positives reported by the ResourceLeakDetector. This can happen as the JIT / GC may be able to figure out that we do not need the tracked object anymore and so already enqueue it for collection before we actually get a chance to close the enclosing ResourceLeak.
Modifications:
- Add ResourceLeakTracker and deprecate the old ResourceLeak
- Fix some javadocs to correctly release buffers.
- Add a unit test for ResourceLeakDetector that shows that ResourceLeakTracker has not the problems.
Result:
No more false-positives reported by ResourceLeakDetector when ResourceLeakDetector.track(...) is used.
Motivation:
42fba015ce changed the implemention of ResourceLeakDetector to improve performance. While this was done a branch was missed that can be removed. Beside this using a Boolean as value for the ConcurrentMap is sub-optimal as when calling remove(key, value) an uncessary instanceof check and cast is needed on each removal.
Modifications:
- Remove branch which is not needed anymore
- Replace usage of Boolean as value type of the ConcurrentMap and use our own special type which only compute hash-code one time and use a == operation for equals(...) to reduce overhead present when using Boolean.
Result:
Faster and cleaner ResourceLeakDetector.
Motivation:
Netty has a flag (io.netty.noUnsafe) for specifying to Netty to not be
unsafe. Yet, when initializing PlatformDependent0, Netty still tries to
be unsafe. For application that specify to Netty to not be unsafe and
run under a security manager, this can lead to an obnoxious (debug
level) stack trace. Since Netty was told not to be unsafe, Netty should
not try to be unsafe.
Modifications:
The initialization logic in PlatformDependent0 should take into account
that Netty was told not to be unsafe. This means that we need to
initialize PlatformDependent#IS_EXPLICIT_NO_UNSAFE as soon as possible,
before the static initializer for PlatformDependent0 has a chance to
run. Thus the following modifications are made:
- initialize PlatformDependent#IS_EXPLICIT_NO_UNSAFE before any other
code in PlatformDependent causes PlatformDependent0 to initialize
- expose the value of PlatformDependent#IS_EXPLICIT_NO_UNSAFE for
reading in PlatformDependent0
- take the value of PlatformDependent#IS_EXPLICIT_NO_UNSAFE into
account in PlatformDependent0
Result:
Netty does not try to be unsafe when told not to be unsafe.
Motivation:
For applications that set their own logger factory, they want that
logger factory to be the one logger factory. Yet, Netty eagerly
initializes this and then triggers initialization of other classes
before the application has had a chance to set its preferred logger
factory.
Modifications:
With this commit there are two key changes:
- Netty does not attempt to eagerly initialize the default logger
factory, only doing so if the application layer above Netty has not
already set a logger factory
- do not eagerly initialize unrelated classes from the logger factory;
while the motivation behind this was to initialize ThreadLocalRandom
as soon as possible in case it has to block reading from /dev/random,
this can be worked around for applications where it is problematic by
setting securerandom.source=file:/dev/urandom in their Java system
security policy (no, it is not less secure; do not even get me
started on myths about /dev/random)
Result:
Netty uses the logger factory that the application prefers, and does not
initialize unrelated classes.
Motivation:
PlatformDependent#getSystemClassLoader may throw a wide variety of exceptions based upon the environment. We should handle all exceptions and continue initializing the slow path if an exception occurs.
Modifications:
- Catch Throwable in cases where PlatformDependent#getSystemClassLoader is used
Result:
Fixes https://github.com/netty/netty/issues/6038
Motiviation:
We used ReferenceCountUtil.releaseLater(...) in our tests which simplifies a bit the releasing of ReferenceCounted objects. The problem with this is that while it simplifies stuff it increase memory usage a lot as memory may not be freed up in a timely manner.
Modifications:
- Deprecate releaseLater(...)
- Remove usage of releaseLater(...) in tests.
Result:
Less memory needed to build netty while running the tests.
Motivation:
00fc239995 introduced a change to HashedWheelTimerTest which attempted to wait for an explicit event notification until more timer events can be added. However HashedWheelTimer will execute the timer Runnable before removing it from the queue and decrementing the total count. This make it difficult for users to know when it is safe to add another timer task as the limit is approached.
Modifications:
- HashedWheelTimer should remove the timer Runnable before executing the task.
Result:
Users can more reliably add new timers when the limit is reached and HashedWheelTimerTest will no longer fail spuriously due to this race condition.
Motivation:
If a stream is not able to send any data (flow control window for the stream is exhausted) but has descendants who can send data then WeightedFairQueueByteDistributor may incorrectly modify the pseudo time and also double add the associated state to the parent's priority queue. The pseudo time should only be modified if a node is moved in the priority tree, and not if there happens to be no active streams in its descendent tree and a descendent is moved (e.g. removed from the tree because it wrote all data and the last data frame was EOS). Also the state objects for WeightedFairQueueByteDistributor should only appear once in any queue. If this condition is violated the pseudo time accounting would be biased at and assumptions in WeightedFairQueueByteDistributor would be invalidated.
Modifications:
- WeightedFairQueueByteDistributor#isActiveCountChangeForTree should not allow re-adding to the priority queue if we are currently processing a node in the distribution algorithm. The distribution algorithm will re-evaluate if the node should be re-added on the tail end of the recursion.
Result:
Fixes https://github.com/netty/netty/issues/5980
Motivation:
If the rate at which new timeouts are created is very high and the created timeouts are not cancelled, then the JVM can crash because of out of heap space. There should be a guard in the implementation to prevent this.
Modifications:
The constructor of HashedWheelTimer now takes an optional max pending timeouts parameter beyond which it will reject new timeouts by throwing RejectedExecutionException.
Result:
After this change, if the max pending timeouts parameter is passed as constructor argument to HashedWheelTimer, then it keeps a track of pending timeouts that aren't yet expired or cancelled. When a new timeout is being created, it checks for current pending timeouts and if it's equal to or greater than provided max pending timeouts, then it throws RejectedExecutionException.
Motivation:
PlatformDependent0 should not be referenced directly when sun.misc.Unsafe is unavailable.
Modifications:
Guard byteArrayBaseOffset with hasUnsafe check.
Result:
PlatformDependent can be initialized when sun.misc.Unsafe is unavailable.
Motivation:
ResourceLeakDetector shows two main problems, racy access and heavy lock contention.
Modifications:
This PR fixes this by doing two things:
1. Replace the sampling counter with a ThreadLocalRandom. This has two benefits.
First, it makes the sampling ration no longer have to be a power of two. Second,
it de-noises the continuous races that fight over this single value. Instead,
this change uses slightly more CPU to decide if it should sample by using TLR.
2. DefaultResourceLeaks need to be kept alive in order to catch leaks. The means
by which this happens is by a singular, doubly-linked list. This creates a
large amount of contention when allocating quickly. This is noticeable when
running on a multi core machine.
Instead, this uses a concurrent hash map to keep track of active resources
which has much better contention characteristics.
Results:
Better concurrent hygiene. Running the gRPC QPS benchmark showed RLD taking about
3 CPU seconds for every 1 wall second when runnign with 12 threads.
There are some minor perks to this as well. DefaultResourceLeak accounting is
moved to a central place which probably has better caching behavior.
Motivation:
PlatformDependent has a hash code algorithm which utilizes UNSAFE for performance reasons. This hash code algorithm must also be consistent with CharSequence objects that represent a collection of ASCII characters. In order to make the UNSAFE versions and CharSequence versions the endianness should be taken into account. However the big endian code was not correct in a few places.
Modifications:
- Correct bugs in PlatformDependent class related to big endian ASCII hash code computation
Result:
Fixes https://github.com/netty/netty/issues/5925
Motivation:
the build doesnt seem to enforce this, so they piled up
Modifications:
removed unused import lines
Result:
less unused imports
Signed-off-by: radai-rosenblatt <radai.rosenblatt@gmail.com>
Motivation:
ResourceLeakDetector reports leak for first call to open(obj) as its leakCheckCnt starts with value 0 and increment subsequently. with value of leakCheckCnt =0, it always returns ResourceLeak. Our application calls ResourceLeakDetector.open(obj) to validate Leak and it fails at very first call even though there is no leak in application.
Modifications:
ResourceLeakDetector.leakCheckCnt value will not be 0 while deriving leak and it will not return incorrect value of ResourceLeak.
Result:
Fix false leak report on first call on ResourceLeakDetector.
Motivation:
NetUtil.bytesToIpAddress does not correctly translate IPv4 address to String. Also IPv6 addresses may not follow minimization conventions when converting to a String (see rfc 5952).
Modifications:
- NetUtil.bytesToIpAddress should correctly handle negative byte values for IPv4
- NetUtil.bytesToIpAddress should leverage existing to string conversion code in NetUtil
Result:
Fixes https://github.com/netty/netty/issues/5821
Motivation:
At the moment we log very confusing messages when trying to load a native library which kind of suggest that the whole loading process failed even if just one mechanism failed and the library could be loaded at the end.
Modifications:
Make the mesage less confusing and also log a successful load of the native library.
Result:
Less confusing logs.
Motivation:
To make it easier to debug why notification of a promise failed we should log extra info and make it consistent.
Modifications:
- Create a new PromiseNotificationUtil that has static methods that can be used to try notify a promise and log.
- Reuse this in AbstractChannelHandlerContext, ChannelOutboundBuffer and PromiseNotifier
Result:
Easier to debug why a promise could not be notified.
Motivation:
We can share the code in retain() and retain(...) and also in release() and release(...).
Modifications:
Share code.
Result:
Less duplicated code.
Motivation:
Windows refuses to load a .DLL file when it's opened by other process.
Recent modification in NativeLibraryLoader causes NativeLibraryLoader to
attempt to load a .DLL before closing its OutputStream. As a result,
loading a .DLL file in Windows always fails.
Modifications:
Close the OutputStream explicitly before loading a shared library.
Result:
Native library loading in Windows works again.
Motivation:
SystemPropertyUtil requires InternalLoggerFactory requires ThreadLocalRandom requires SystemPropertyUtil. This can lead to a dead-lock.
Modifications:
Ensure ThreadLocalRandom does not require SystemPropertyUtil during initialization.
Result:
No more deadlock possible.
Motivation:
Sometimes it is useful to be able to wrap an existing memory address (a.k.a pointer) and create a ByteBuf from it. This way its easier to interopt with other libraries.
Modifications:
Add a new Unpooled.wrappedBuffer(....) method that takes a memory address.
Result:
Be able to wrap an existing memory address into a ByteBuf.
Motivation:
As the issue #5539 say, the OpenSsl.class will throw `java.lang.UnsatisfiedLinkError: org.apache.tomcat.jni.Library.version(I)I` when it is invoked. This path try to resolve the problem by modifying the native library loading logic of OpenSsl.class.
Modifications:
The OpenSsl.class loads the tcnative lib by `NativeLibraryLoader.loadFirstAvailable()`. The native library will be loaded in the bundle `netty-common`'s ClassLoader, which is diff with the native class's ClassLoader. That is the root cause of throws `UnsatisfiedLinkError` when the native method is invoked.
So, it should load the native library by the its bundle classloader firstly, then the embedded resources if failed.
Result:
First of all, the error threw by native method problem will be resolved.
Secondly, the native library should work as normal in non-OSGi env. But, this is hard. The loading logic of `Library.class` in `netty-tcnative` bundle is simple: try to load the library in PATH env. If not found, it falls back to the originally logic `NativeLibraryLoader.loadFirstAvailable()`.
Signed-off-by: XU JINCHUAN <xsir@msn.com>
Motivation:
When try to call Cleaner.run() via reflection on Java9 you may see an IllegalAccessException.
Modifications:
Just cast the Cleaner to Runnable to prevent IllegalAccessException to be raised.
Result:
Free direct buffers also work on Java9+ as expected.
Motivation:
Our current strategy in NativeLibraryLoader is to mark the temporary .so file to be deleted on JVM exit. This has the drawback to not delete the file in the case the JVM dies or is killed.
Modification:
Just directly try to delete the file one we loaded the native library and if this fails mark the file to be removed once the JVM exits.
Result:
Less likely to have temporary files still on the system in case of JVM kills.
Motivation:
According to the Oracle documentation:
> java.net.preferIPv4Stack (default: false)
>
> If IPv6 is available on the operating system, the underlying native
> socket will be an IPv6 socket. This allows Java applications to connect
> to, and accept connections from, both IPv4 and IPv6 hosts.
>
> If an application has a preference to only use IPv4 sockets, then this
> property can be set to true. The implication is that the application
> will not be able to communicate with IPv6 hosts.
which means, if DnsNameResolver returns an IPv6 address, a user (or
Netty) will not be able to connect to it.
Modifications:
- Move the code that retrieves java.net.prefer* properties from
DnsNameResolver to NetUtil
- Add NetUtil.isIpV6AddressesPreferred()
- Revise the API documentation of NetUtil.isIpV*Preferred()
- Set the default resolveAddressTypes to IPv4 only when
NetUtil.isIpv4StackPreferred() returns true
Result:
- Fixes#5657
Motiviation:
Preparing platform dependent code for using unsafe requires executing
privileged code. The privileged code for initializing unsafe is executed
in a manner that would require all code leading up to the initialization
to have the requisite permissions. Yet, in a restrictive environment
(e.g., under a security policy that only grants the requisite
permissions the Netty common jar but not to application code triggering
the Netty initialization), then initializing unsafe will not succeed
even if the security policy would otherwise permit it.
Modifications:
This commit marks the necessary blocks as privileged. This enables
access to the necessary resources for initialization unsafe. The idea is
that we are saying the Netty code is trusted, and as long as the Netty
code has been granted the necessary permissions, then we will allow the
caller access to these resources even though the caller itself might not
have the requisite permissions.
Result:
Unsafe can be initialized in a restrictive security environment.
Motivation:
Its not clear that the capacity is per thread.
Modifications:
Rename system property to make it more clear that the recycler capacity is per thread.
Result:
Less confusing.
Motivation:
We not need to do an extra conditional check in retain(...) as we can just check for overflow after we did the increment.
Modifications:
- Remove extra conditional check
- Add test code.
Result:
One conditional check less.
Motivation:
If the user uses 0 as quiet period we should shutdown without any delay if possible.
Modifications:
Ensure we not introduce extra delay when a shutdown quit period of 0 is used.
Result:
EventLoop shutdown as fast as expected.
Current constant pool holds all data within HashMap and all access to this HashMap is done via synchronized blocks. Thus CuncurrentHashMap will be here more efficient as it designed for higher throughput and will use less locks. Also valueOf method was not very efficient as it performed get operation 2 times.
Modifications :
HashMap -> PlatformDependent.newConcurrentHashMap().
ValueOf is more efficient now, threadsafe and uses less locks. Downside is that final T tempConstant = newConstant(nextId(), name); could be called more than 1 time during high contention.
Result :
Less contention, cleaner code.
Motivation:
We offer DefaultEventExecutorGroup as an EventExecutorGroup which return OrderedEventExecutor and so provide strict ordering of event execution. One limitations of this implementation is that each contained DefaultEventExecutor will always be tied to a single thread, which can lead to a very unbalanced execution as one thread may be super busy while others are idling.
Modifications:
- Add NonStickyEventExecutorGroup which can be used to wrap another EventExecutorGroup (like UnorderedThreadPoolEventExecutor) and expose ordering while not be sticky with the thread that is used for a given EventExecutor. This basically means that Threads may change between execution of tasks for an EventExecutor but ordering is still guaranteed.
Result:
Better utalization of threads in some use-cases.
Motivation:
To better restrict resource usage we should limit the number of WeakOrderQueue instances per Thread. Once this limit is reached object that are recycled from a different Thread then the allocation Thread are dropped on the floor.
Modifications:
Add new system property io.netty.recycler.maxDelayedQueuesPerThread and constructor that allows to limit the max number of WeakOrderQueue instances per Thread for Recycler instance. The default is 2 * cores (the same as the default number of EventLoop instances per EventLoopGroup).
Result:
Better way to restrict resource / memory usage per Recycler instance.
Motivation:
Commons logger is dead and not updated for more than 2 years. #5615.
Modifications:
Added @Deprecated annotation to CommonsLoggerFactory and CommonsLogger.
Result:
Commons logger now deprecated.
Motivation:
When Netty components are initialized, Netty attempts to determine if it
has access to unsafe. If Netty is not able to access unsafe (because of
security permissions, or because the JVM was started with an explicit
flag to tell Netty to not look for unsafe), Netty logs an info-level
message that looks like a warning:
Your platform does not provide complete low-level API for accessing
direct buffers reliably. Unless explicitly requested, heap buffer will
always be preferred to avoid potential system unstability.
This log message can appear in applications that depend on Netty for
networking, and this log message can be scary to end-users of such
platforms. This log message should not be emitted if the application was
started with an explicit flag telling Netty to not look for unsafe.
Modifications:
This commit refactors the unsafe detection logic to expose whether or
not the JVM was started with a flag telling Netty to not look for
unsafe. With this exposed information, the log message on unsafe being
unavailable can be modified to not be emitted when Netty is explicitly
told to not look for unsafe.
Result:
No log message is produced when unsafe is unavailable because Netty was
told to not look for it.
Motivation:
AbstractConstant.compareTo seems complex and hard to understand. Also it allocates unnecessary 1 byte in direct buffer and holds unnecessary pointer to this byte butter.
Modifications:
uniquifier (id) variable now initialized during Constant creation and thus no need in volatile and no need in uniquifier() method as it could be easily replaced with AtomicLong.
Result:
Every Constant instance now consumes less bytes for pointer, don't consume anything in direct buffer.
Motivation:
Old code doesn't needed anymore due to logger factory initialization.
Modifications :
Removed static section and useless static variables;
Logging concatenations replaced with placeholders.
Result:
Cleaner, simpler code doing the same
Motivation:
Some usages of findNextPositivePowerOfTwo assume that bounds checking is taken care of by this method. However bounds checking is not taken care of by findNextPositivePowerOfTwo and instead assert statements are used to imply the caller has checked the bounds. This can lead to unexpected non power of 2 return values if the caller is not careful and thus invalidate any logic which depends upon a power of 2.
Modifications:
- Add a safeFindNextPositivePowerOfTwo method which will do runtime bounds checks and always return a power of 2
Result:
Fixes https://github.com/netty/netty/issues/5601
Motivation:
NewLine initializing is complex, with unnecessary allocations and non-standard.
Static section is overloaded with StringBuilders for simple "s" + "s" concatenation pattern that compiler optimizes perfectly.
Modifications:
NewLine initializing replaced with standard System.getProperty("line.separator").
Removed StringBuilders in static section.
Result:
Less complex code.
Motivation:
When we try to close the Channel due a timeout we need to ensure we not log if the notification of the promise fails as it may be completed in the meantime.
Modifications:
Add another constructor to ChannelPromiseNotifier and PromiseNotifier which allows to log on notification failure.
Result:
No more miss-leading logs.
Motivation:
At the moment the Recyler is very sensitive to allocation bursts which means that if there is a need for X objects for only one time these will most likely end up in the Recycler and sit there forever as the normal workload only need a subset of this number.
Modifications:
Add a ratio which sets how many objects should be pooled for each new allocation. This allows to slowly increase the number of objects in the Recycler while not be to sensitive for bursts.
Result:
Less unused objects in the Recycler if allocation rate sometimes bursts.
Motivation:
Using Attribute.remove() and Attribute.getAndRemove() in a multi-threaded enviroment has its drawbacks. Make sure we document these.
Modifications:
Add javadocs and mark Attribute.remove() and Attribute.getAndRemove() as @Deprecated.
Result:
Hopefully less suprising behaviour.
Motivation:
We used a very high number for DEFAULT_INITIAL_MAX_CAPACITY (over 200k) which is not very relastic and my lead to very surprising memory usage if allocations happen in bursts.
Modifications:
Use a more sane default value of 32k
Result:
Less possible memory usage by default
Motivation:
AbstractReferenceCounted as independent conditional statements to check the bounds of the retain IllegalReferenceCountException condition. One of the exceptions also uses the incorrect increment.
Modifications:
- Combined independent conditional checks into 1 where possible
- Correct IllegalReferenceCountException with incorrect increment
- Remove the subtract to check for overflow and re-use the addition and check for overflow to remove 1 arithmetic operation (see http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.18.2)
Result:
AbstractReferenceCounted has less independent branch statements and more correct IllegalReferenceCountException. Compilation size of AbstractReferenceCounted.retain() is reduced from 58 bytes to 47 bytes.
Motivation:
We use a shared capacity per Stack for all its WeakOrderQueue elements. These relations are stored in a WeakHashMap to allow dropping these if memory pressure arise. The problem is that we not "reclaim" previous reserved space when this happens. This can lead to a Stack which has not shared capacity left which then will lead to an AssertError when we try to allocate a new WeakOderQueue.
Modifications:
- Ensure we never throw an AssertError if we not have enough space left for a new WeakOrderQueue
- Ensure we reclaim space when WeakOrderQueue is collected.
Result:
No more AssertError possible when new WeakOrderQueue is created and also correctly reclaim space that was reserved from the shared capacity.
Motivation:
Due an implementation flaw in DefaultAttributeMap it was possible that an attribute and its stored value/key could not be collected until the DefaultAttributeMap could be collected. This can lead to unexpected memory usage and strong reachability of objects that should be collected.
Modifications:
Use an special empty DefaultAttribute as head of the each bucket which will not store any key / value. With this change everything can be collected as expected as we not use any DefaultAttribute created by the user as head of a bucket.
Result:
DefaultAttributeMap does not store user data and thus the lifetime of this user data is not tied to the lifetime of the DefaultAttributeMap.
Motivation:
Commit afafadd3d7 introduced a change which stored the Stack in the WeakOrderQueue as field. This unfortunally had the effect that it was not removed from the WeakHashMap anymore as the Stack also is used as key.
Modifications:
Do not store a reference to the Stack in WeakOrderQueue.
Result:
WeakOrderQueue can be collected correctly again.
Motivation:
When resolving localhost on Windows where the hosts file does not contain a localhost entry by default, the resulting InetAddress object returned by the resolver does not have the hostname set so that getHostName returns the ip address 127.0.0.1. This behaviour is inconsistent with Windows where the hosts file does contain a localhost entry and with Linux in any case. It breaks at least some unit tests.
Modifications:
Create the LOCALHOST4 and LOCALHOST6 objects with hostname localhost in addition to the address.
Add unit test domain localhost to DnsNameResolverTest to check the resolution of localhost with ipv4 at least.
Result:
The resolver returns a InetAddress object for localhost with the hostname localhost in all cases.
Motivation:
The Java version is used for platform dependent logic. Yet, the logic
for acquiring the Java version requires special permissions (the runtime
permission "getClassLoader") that some downstream projects will never
grant. As such, these projects are doomed to have Netty act is their
Java major version is six. While there are ways to maintain the same
logic without requiring these special permissions, the logic is
needlessly complicated because it relies on loading classes that exist
in version n but not version n - 1. This complexity can be removed. As a
bonanza, the dangerous permission is no longer required.
Modifications:
Rather than attempting to load classes that exist in version n but not
in version n - 1, we can just parse the Java specification version. This
only requires a begign property (property permission
"java.specification.version") and is simple.
Result:
Acquisition of the Java version is safe and simple.
Motivation:
The clean method in java.base/jdk.internal.ref.Cleaner is not accessible
to methods outside java.base. This prevents Cleaner0.freeDirectBuffer
from actually calling the clean method on JDK9.
The issue could have been caught earlier if Cleaner0 is initialized when
PlatformDependent0 is initialized and logging statements in the static
initializer in Cleaner0 would be close to the logging statements in the
static initializer in PlatformDependent0.
Modifications:
Try casting the cleaner obtained from a ByteBuffer to Runnable and use
Runnable.run if possible. All Cleaners in JDK9 implements Runnable. Fall
back to the clean method if the cleaner does not implement Runnable.
The fallback preserves the behavior on JDK8 and earlier.
Try to free the direct ByteBuffer allocated during static initialization
of PlatformDependent0. This cause Cleaner0 to be initialized when
PlatformDependent0 is initialized, and logging statements from the
static initializers will be close together.
Result:
Cleaner0.freeDirectBuffer works as intended on JDK9 and logging shows
that Cleaner0.freeDirectBuffer works as intended.
Motivation:
A recent change to DefaultThreadFactory modified it so that it is sticky
with respect to thread groups. In particular, this change made it so
that DefaultThreadFactory would hold on to the thread group that created
it, and then use that thread group to create threads.
This can have problematic semantics since it can lead to violations of a
tenet of thread groups that a thread can only modify threads in its own
thread group and descendant thread groups. With a sticky thread group, a
thread triggering the creation of a new thread via
DefaultThreadFactory#newThread will be modifying a thread from the
sticky thread group which will not necessarily be its own nor a
descendant thread group. When a security manager is in place that
enforces this requirement, these modifications are now impossible. This
is especially problematic in the context of Netty because certain global
singletons like GlobalEventExecutor will create a
DefaultThreadFactory. If all DefaultThreadFactory instances are sticky
about their thread groups, it means that submitting tasks to the
GlobalEventExecutor singleton can cause a thread to be created from the
DefaultThreadFactory sticky thread group, exactly the problem with
DefaultThreadFactory being sticky about thread groups. A similar problem
arises from the ThreadDeathWatcher.
Modifications:
This commit modifies DefaultThreadFactory so that a null thread group
can be set with the behavior that all threads created by such an
instance will inherit the default thread group (the thread group
provided by the security manager if there is one, otherwise the thread
group of the creating thread). The construction of the instances of
DefaultThreadFactory used by the GlobalEventExecutor singleton and
ThreadDeathWatcher are modified to use this behavior. Additionally, we
also modify the chained constructor invocations of the
DefaultThreadFactory that do not have a parameter to specify a thread
group to use the thread group from the security manager is available,
otherwise the creating thread's thread group. We also add unit tests
ensuring that all of this behavior is maintained.
Result:
It will be possible to have DefaultThreadFactory instances that are not
sticky about the thread group that led to their creation. Instead,
threads created by such a DefaultThreadFactory will inherit the default
thread group which will either be the thread group from the security
manager or the current thread's thread group.
Motivation:
Currently, the recycler max capacity it's only enforced on the
thread-local stack which is used when the recycling happens on the
same thread that requested the object.
When the recycling happens in a different thread, then the objects
will be queued into a linked list (where each node holds N objects,
default=16). These objects are then transfered into the stack when
new objects are requested and the stack is empty.
The problem is that the queue doesn't have a max capacity and that
can lead to bad scenarios. Eg:
- Allocate 1M object from recycler
- Recycle all of them from different thread
- Recycler WeakOrderQueue will contain 1M objects
- Reference graph will be very long to traverse and GC timeseems to be negatively impacted
- Size of the queue will never shrink after this
Modifications:
Add some shared counter which is used to manage capacity limits when recycle from different thread then the allocation thread. We modify the counter whenever we allocate a new Link to reduce the overhead of increment / decrement it.
Result:
More predictable number of objects mantained in the recycler pool.
Motivation:
This change is part of the change done in PR #5395 to provide an `AUTO_FLUSH` capability.
Splitting this change will enable to try other ways of implementing `AUTO_FLUSH`.
Modifications:


Two methods:
```java
void executeAfterEventLoopIteration(Runnable task);


boolean removeAfterEventLoopIterationTask(Runnable task);
```
are added to `SingleThreadEventLoop` class for adding/removing a task to be executed at the end of current/next iteration of this `eventloop`.
In order to support the above, a few methods are added to `SingleThreadEventExecutor`
```java
protected void afterRunningAllTasks() { }
```
This is invoked after all tasks are run for this executor OR if the passed timeout value for `runAllTasks(long timeoutNanos)` is expired.
Added a queue of `tailTasks` to `SingleThreadEventLoop` to hold all tasks to be executed at the end of every iteration.


Result:


`SingleThreadEventLoop` now has the ability to execute tasks at the end of an eventloop iteration.
Motivation:
Today when awaiting uninterruptibly on a default promise, a race
condition can lead to a missed signal. Quite simply, the check for
whether the condition holds is not made inside a lock before
waiting. This means that the waiting thread can enter the wait after the
promise has completed and will thus not be notified, thus missing the
signal. This leads to the waiting thread to enter a timed wait that will
only trip with the timeout elapses leading to unnecessarily long waits
(imagine a connection timeout, and the waiting thread missed the signal
that the connection is ready).
Modification:
This commit fixes this missed signal by checking the condition inside a
lock. We also add a test that reliably fails without the non-racy
condition check.
Result:
Timed uninterruptible waits on default promise will not race against the
condition and possibly wait longer than necessary.
Motivation:
ExecutorService.invoke*(...) methods may block by API definition. This can lead to deadlocks if called from inside the EventLoop in SingleThreadEventExecutor as it only has one Thread that does all the work.
Modifications:
Throw a RejectedExectionException if someone tries to call SingleThreadEventExecutor.invoke*(...) while in the EventLoop.
Result:
No more deadlock possible.
Motivation:
The current DnsNameResolver does not support search domains resolution. Search domains resolution is supported out of the box by the java.net resolver, making the DnsNameResolver not able to be a drop in replacement for io.netty.resolver.DefaultNameResolver.
Modifications:
The DnsNameResolverContext resolution has been modified to resolve a list of search path first when it is configured so. The resolve method now uses the following algorithm:
if (hostname is absolute (start with dot) || no search domains) {
searchAsIs
} else {
if (numDots(name) >= ndots) {
searchAsIs
}
if (searchAsIs wasn't performed or failed) {
searchWithSearchDomainsSequenciallyUntilOneSucceeds
}
}
The DnsNameResolverBuilder provides configuration for the search domains and the ndots value. The default search domains value is configured with the OS search domains using the same native configuration the java.net resolver uses.
Result:
The DnsNameResolver performs search domains resolution when they are present.
Motivation:
DefaultPromise has a listeners member variable which is volatile to allow for an optimization which makes notification of listeners less expensive when there are no listeners to notify. However this change makes all other operations involving the listeners member variable more costly. This optimization which requires listeners to be volatile can be removed to avoid volatile writes/reads for every access on the listeners member variable.
Modifications:
- DefaultPromise listeners is made non-volatile and the null check optimization is removed
Result:
DefaultPromise.listeners is no longer volatile.
Motivation:
In commit f984870ccc I made a change which operated under invalide assumption that tasks executed by an EventExecutor will always be processed in a serial fashion. This is true for SingleThreadEventExecutor sub-classes but not part of the EventExecutor interface contract.
Because of this change implementations of EventExecutor which not strictly execute tasks in a serial fashion may miss events before handlerAdded(...) is called. This is strictly speaking not correct as there is not guarantee in this case that handlerAdded(...) will be called as first task (as there is no ordering guarentee).
Cassandra itself ships such an EventExecutor implementation which has no strict ordering to spread load across multiple threads.
Modifications:
- Add new OrderedEventExecutor interface and let SingleThreadEventExecutor / EventLoop implement / extend it.
- Only expose "restriction" of skipping events until handlerAdded(...) is called for OrderedEventExecutor implementations
- Add ThreadPoolEventExecutor implementation which executes tasks in an unordered fashion. This is used in added unit test but can also be used for protocols which not expose an strict ordering.
- Add unit test.
Result:
Resurrect the possibility to implement an EventExecutor which does not enforce serial execution of events and be able to use it with the DefaultChannelPipeline.
Motivation:
DefaultPromise has a listeners member variable which is volatile to allow for an optimization which makes notification of listeners less expensive when there are no listeners to notify. However this change makes all other operations involving the listeners member variable more costly. This optimization which requires listeners to be volatile can be removed to avoid volatile writes/reads for every access on the listeners member variable.
Modifications:
- DefaultPromise listeners is made non-volatile and the null check optimization is removed
Result:
DefaultPromise.listeners is no longer volatile.
Motivation:
The logging statements in i.n.u.c.DefaultPromise do not emit the
caught Throwable when a Throwable is thrown while a listener is being
notified of completed or progressed operations.
Modifications:
This issue arises because the logging message has a single placeholder
but is passing two additional arguments, the second one being the
caught Throwable that is thus quietly not logged. We address this by
modifying the logging statements to ensure the caught Throwable is
logged. In this case, the preferred approach is to use the logger
override that accepts a message and a Throwable parameter since logger
implementations might have special handling for this case.
Result:
Log messages from i.n.u.c.DefaultPromise when a Throwable is thrown
while notifying a listener of completed or progressed operations will
contain the caught Throwable.
Motivation:
A race detector found that DefaultPromise.listeners is improperly synchronized [1].
Worst case a listener will not be executed when the promise is completed.
Modifications:
Make DefaultPromise.listeners a volatile.
Result:
Hopefully, DefaultPromise is more correct under concurrent execution.
[1] https://github.com/grpc/grpc-java/issues/2015
Motivation:
Currently in the single threaded and global event executors when the scheduled task queue is drained, there is a call to hasScheduledTasks(). If there are scheduled tasks then the the code polls the queue for tasks. The poll method duplicates the exact logic of hasScheduledTasks(). This involves two calls to nanoTime when one seems sufficient.
Modifications:
Directly poll the queue for tasks and break if the task returned is null.
Result:
Should be no noticeable impact on functionality. Two calls to nanoTime have been coarsened into a single call.
Motivation:
Project Jigsaw in JDK9 has moved the direct byte buffer cleaner from
sun.misc.Cleaner to java.lang.ref.Cleaner$Cleanable. This cause the
current platform tests to throw a ClassNotFoundException, disabling the
use of direct byte buffer cleaners.
Modifications:
I use reflection to find the clean method in either sun.misc.Cleaner or
java.lang.ref.Cleaner$Cleanable.
Result:
Netty uses direct byte buffers on JDK9 as it already do on earlier JDKs.
Motivation:
In JDK9 heap byte buffers have an address field, so we have to remove
the current check as it is invalid in JDK9.
Modifications:
Removed the address field check for heap byte buffers.
Result:
Netty continues to find sun.misc.Unsafe in JDK9 as in previous JDKs.
Motivation:
Netty's platform dependent parts should know about JDK9.
Modifications:
JDK9 introduce Runtime$Version Runtime.version() which has an int major()
method that always return the major Java version. I call that method to
get the Java major version.
Result:
Netty will recognize all future JDK versions.
Motivation:
HPACK Encoder has a data structure which is similar to a previous version of DefaultHeaders. Some of the same improvements can be made.
Motivation:
- Enforce the restriction that the Encoder's headerFields length must be a power of two so we can use masking instead of modulo
- Use AsciiString.hashCode which already has optimizations instead of having yet another hash code algorithm in Encoder
Result:
Fixes https://github.com/netty/netty/issues/5357
Motivation:
PlatformDependent attempts to use reflection to get the underlying char[] (or byte[]) from String objects. This is fragile as if the String implementation does not utilize the full array, and instead uses a subset of the array, this optimization is invalid. OpenJDK6 and some earlier versions of OpenJDK7 String have the capability to use a subsection of the underlying char[].
Modifications:
- PlatformDependent should not attempt to use the underlying array from String (or other data types) via reflection
Result:
PlatformDependent hash code generation for CharSequence does not depend upon specific JDK implementation details.
Motivation:
We recently added the ResourceLeakDetectorFactory but missed to updated HashedWheelTimer to use it.
Modifications:
- Add new abstract method to ResourceLeakDetectorFactory that allows to provide also samplingInterval and maxActive args.
- Deprecate most constructors in ResourceLeakDetector and add doc explaining that people should use ResourceLeakDetectorFactory
Result:
Custom ResourceLeakDetectorFactory will also be used in HashedWheelTimer if configured.
Motivation:
Sometimes a shared HashedWheelTimer can not easily be stopped in a good place. If the worker thread is daemon this is not a big deal and we should allow to not log a leak.
Modifications:
Add another constructor which allows to disable resource leak detection if worker thread is used.
Result:
Not log resource leak when HashedWheelTimer is not stopped and the worker thread is a deamon thread.
Motivation:
Some Netty use cases may want to configure the max allowed stack depth for promise listener notification.
Modifications:
- Add a system property so that this value can be configured.
Result:
DefaultPromise's max stack depth is configurable.
Motivation:
PR #5355 modified interfaces to reduce GC related to the HPACK code. However this came with an anticipated performance regression related to HpackUtil.equals due to AsciiString's increase cost of charAt(..). We should mitigate this performance regression.
Modifications:
- Introduce an equals method in PlatformDependent which doesn't leak timing information and use this in HpcakUtil.equals
Result:
Fixes https://github.com/netty/netty/issues/5436
Motivation:
It is good to have used dependencies and plugins up-to-date to fix any undiscovered bug fixed by the authors.
Modification:
Scanned dependencies and plugins and carefully updated one by one.
Result:
Dependencies and plugins are up-to-date.
Motiviation:
Sometimes it is useful to allow to specify a custom strategy to handle rejected tasks. For example if someone tries to add tasks from outside the eventloop it may make sense to try to backoff and retries and so give the executor time to recover.
Modification:
Add RejectedEventExecutor interface and implementations and allow to inject it.
Result:
More flexible handling of executor overload.
Motivation:
To restrict the memory usage of a system it is sometimes needed to adjust the number of max pending tasks in the tasks queue.
Modifications:
- Add new constructors to modify the number of allowed pending tasks.
- Add system properties to configure the default values.
Result:
More flexible configuration.
