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:
We saw some sporadic test failures for GlobalEventExecutorTest.testAutomaticStartStop test. This is caused parallel execution of tests in combination with assert checks that will be affected.
Modifications:
Remove fragile assert checks.
Result:
No more sporadic test failures
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:
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:
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:
AsciiString.hashCode(o) , if "o" is a subString, the hash code is not always same, when netty’s version is 4.1.1.Final and jdk’s version is 1.6.
Modifications:
Use a test to assert hash codes are equal between a new string and any sub string (a part of a char array),If their values are equal.
Result:
Create a test method to AsciiStringCharacterTest.
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:
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
Modifications:
DefaultPromise provides a ThreadLocal queue to protect against StackOverflowError because of executors which may immediately execute runnables instead of queue them (i.e. ImmediateEventExecutor). However this may be better addressed by fixing these executors to protect against StackOverflowError instead of just fixing for a single use case. Also the most commonly used executors already provide the desired behavior and don't need the additional overhead of a ThreadLocal queue in DefaultPromise.
Modifications:
- Remove ThreadLocal queue from DefaultPromise
- Change ImmediateEventExecutor so it maintains a queue of runnables if reentrant condition occurs
Result:
DefaultPromise StackOverflowError code is simpler, and ImmediateEventExecutor protects against StackOverflowError.
Motivation:
f2ed3e6ce8 removed the previous mechanism for StackOverflowError because it didn't work in all cases (i.e. ImmediateExecutor). However if a chain of listeners which complete other promises is formed there is still a possibility of a StackOverflowError.
Modifications:
- Use a ThreadLocal to save any DefaultPromises which could not be notified due to the stack being too large. After the first DefaultPromise on the stack completes notification this ThreadLocal should be used to notify any DefaultPromises which have not yet been notified.
Result:
DefaultPromise has StackOverflowError protection that works with all EventExecutor types.
Motivation:
Recycler.recycle(...) should not be used anymore and be replaced by Handle.recycle().
Modifications:
Mark it as deprecated and update usage.
Result:
Correctly document deprecated api.
Motivation:
DomainMappingBuilder should have been named as DomainNameMappingBuilder
because it builds a DomainNameMapping.
Modifications:
- Add DomainNameMappingBuilder that does the same job with
DomainMappingBuilder
- Deprecate DomainMappingBuilder and delegate its logic to
DomainNameMappingBuilder
- Remove the references to the deprecated methods and classes related
with domain name mapping
- Miscellaneous:
- Fix Javadoc of DomainNameMapping.asMap()
- Pre-create the unmodifiable map in DomainNameMapping
Result:
- Consistent naming
- Less use of deprecated API
Motivation:
DomainNameMapping.entries() returns Set<Map.Entry<String, V>>, which
doesn't sound very natural.
Modifications:
Replace entries() with asMap() which returns a Map<String, V> instead.
Result:
- Better looking API
- User can do a lookup because it's a Map
Motivation:
See #4200.
Modifications:
Add DomainNameMapping.entries to allow retrieving the domain match lists.
Result:
People can use DomainNameMapping.entries to retrive the match list in DomainNameMapping.
Motivation:
KObjectHashMap.remove(int index) attempts to move back items which may have been displaced because their spot in the hash based array was taken by another item. If this happens the nextIndex reference in PrimitiveIterator will not be updated. At this time the PrimitiveEntry will reference the incorrect index and may result in a NPE.
Modifications:
- If KObjectHashMap.remove(int index) moves entries back then PrimitiveIterator should adjust its nextIndex
Result:
PrimitiveIterator.remove() updates its internal state to reference the new nextIndex and will not NPE.
Fixes https://github.com/netty/netty/issues/5198
Motivation:
The LateListener logic is prone to infinite loops and relies on being processed in the EventExecutor's thread for synchronization, but this EventExecutor may not be constant. An infinite loop can occur if the EventExecutor's execute method does not introduce a context switch in LateListener.run. The EventExecutor can be changed by classes which inherit from DefaultPromise. For example the DefaultChannelPromise will return w/e EventLoop the channel is registered to, but this EventLoop can change (re-registration).
Modifications:
- Remove the LateListener concept and instead use a single Object to maintain the listeners while still preserving notification order
- Make the result member variable an atomic variable so it can be outside the synchronized(this) blocks
- Cleanup/simplify existing state management code
Result:
Fixes https://github.com/netty/netty/issues/5185
Motivation:
Currently the default log level when running tests is debug. When
running the build on the CI server it might be nice to avoid this debug
level and allow for the level to be configured.
Modifications:
Added a logback-test.xml configuration that has been added to the
common module. This allows for the logLevel to be configured.
The default level will still be debug.
Result:
The log level can now be configured from the command line:
$ mvn test -DlogLevel=error
Motivation:
It's better to make all InternalLoggerFactory implementations be singletons according to the discussions in #5047
Modifications:
Make all InternalLoggerFactory implementations be singletons and hide the construtors.
Result:
All InternalLoggerFactory implementations be singletons.
Motivation:
See #3095
Modifications:
Add Log4J2LoggerFactory and Log4J2Logger which is an InternalLogger implementation based on log4j2.
Result:
The user can use log4j2 directly without a special slf4j binding.
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:
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:
See #4855
Modifications:
Unfortunately, unescapeCsv cannot be used here because the input could be a CSV line like `"a,b",c`. Hence this patch adds unescapeCsvFields to parse a CSV line and split it into multiple fields and unescaped them. The unit tests should define the behavior of unescapeCsvFields.
Then this patch just uses unescapeCsvFields to implement `CombinedHttpHeaders.getAll`.
Result:
`CombinedHttpHeaders.getAll` will return the unescaped values of a header.
Motivation:
In AsciiString.trim, last should be `arrayOffset() + length() - 1`. See #4741.
Modifications:
Fix the last value.
Result:
AsciiString.trim works correctly.
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:
PriorityStreamByteDistributor uses a homegrown algorithm which distributes bytes to nodes in the priority tree. PriorityStreamByteDistributor has no concept of goodput which may result in poor utilization of network resources. PriorityStreamByteDistributor also has performance issues related to the tree traversal approach and number of nodes that must be visited. There also exists some more proven algorithms from the resource scheduling domain which PriorityStreamByteDistributor does not employ.
Modifications:
- Introduce a new ByteDistributor which uses elements from weighted fair queue schedulers
Result:
StreamByteDistributor which is sensitive to priority and uses a more familiar distribution concept.
Fixes https://github.com/netty/netty/issues/4462
Motivation:
The KObjectHashMapTest is in a directory called "io.netty.util.collection" rather than "io/netty/util/collection". This causes the generated tests to be created in the wrong directory as well.
Modifications:
Moved the file.
Result:
Fixes#4546
Motivation:
Related to issue #4564.
AsciiString.contentEqualsIgnoreCase fails when comparing two AsciiStrings of the same length
Modifications:
Compare the values of the first AsciiString to the second AsciiString
Result:
AsciiString.contentEqualsIgnoreCase works as expected
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:
HttpHeaders already has specific methods for such popular and simple headers like "Host", but if I need to convert POST raw body to string I need to parse complex ContentType header in my code.
Modifications:
Add getCharset and getCharsetAsString methods to parse charset from Content-Length header.
Result:
Easy to use utility method.
Motivation:
The AsciiString.hashCode() method can be optimized. This method is frequently used while to build the DefaultHeaders data structure.
Modification:
- Add a PlatformDependent hashCode algorithm which utilizes UNSAFE if available
Result:
AsciiString hashCode is faster.
Motivation:
The HTTP/2 RFC (https://tools.ietf.org/html/rfc7540#section-8.1.2) indicates that header names consist of ASCII characters. We currently use ByteString to represent HTTP/2 header names. The HTTP/2 RFC (https://tools.ietf.org/html/rfc7540#section-10.3) also eludes to header values inheriting the same validity characteristics as HTTP/1.x. Using AsciiString for the value type of HTTP/2 headers would allow for re-use of predefined HTTP/1.x values, and make comparisons more intuitive. The Headers<T> interface could also be expanded to allow for easier use of header types which do not have the same Key and Value type.
Motivation:
- Change Headers<T> to Headers<K, V>
- Change Http2Headers<ByteString> to Http2Headers<CharSequence, CharSequence>
- Remove ByteString. Having AsciiString extend ByteString complicates equality comparisons when the hash code algorithm is no longer shared.
Result:
Http2Header types are more representative of the HTTP/2 RFC, and relationship between HTTP/2 header name/values more directly relates to HTTP/1.x header names/values.
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:
When dealing with case insensitive headers it can be useful to have a case insensitive contains method for CharSequence.
Modifications:
- Add containsCaseInsensative to AsciiString
Result:
More expressive utility method for case insensitive CharSequence.
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=0 to disable recycling completely.
Result:
It's possible to disable recycling now.
Motivation:
A degradation in performance has been observed from the 4.0 branch as documented in https://github.com/netty/netty/issues/3962.
Modifications:
- Simplify Headers class hierarchy.
- Restore the DefaultHeaders to be based upon DefaultHttpHeaders from 4.0.
- Make various other modifications that are causing hot spots.
Result:
Performance is now on par with 4.0.
Motivation:
It would be useful to support the Java `Map` interface in our primitive maps.
Modifications:
Renamed current methods to "pXXX", where p is short for "primitive". Made the template for all primitive maps extend the appropriate Map interface.
Result:
Fixes#3970
Motivation:
There is an error in the ByteString test logic which is resulting in test failures.
Modifications:
- Fix the loop iteration to use the loop iteration variable instead of a fixed index.
Result:
Tests are less buggy.
Motivation:
In the SslHandler we schedule a timeout at which we close the Channel if a timeout was detected during close_notify. Because this can race with notify the flushFuture we can see an IllegalStateException when the Channel is closed.
Modifications:
- Use a trySuccess() and tryFailure(...) to guard against race.
Result:
No more race.
Motivation:
The ByteString class currently assumes the underlying array will be a complete representation of data. This is limiting as it does not allow a subsection of another array to be used. The forces copy operations to take place to compensate for the lack of API support.
Modifications:
- add arrayOffset method to ByteString
- modify all ByteString and AsciiString methods that loop over or index into the underlying array to use this offset
- update all code that uses ByteString.array to ensure it accounts for the offset
- add unit tests to test the implementation respects the offset
Result:
ByteString and AsciiString can represent a sub region of a byte[].
