Motivation:
In order to prevent a regression, add test case for a bug that caused a CompositeByteBuf to not release its components.
Modifications:
Add a test case that asserts a CompositeByteBuf's component buffers have indeed been released.
Result:
AbstractCompositeByteBuf gains a test case that will prevent future regressions.
Allow users of Netty to plug in their own leak detector for the purpose
of instrumentation.
Motivation:
We are rolling out a large Netty deployment and want to be able to
track the amount of leaks we're seeing in production via custom
instrumentation. In order to achieve this today, I had to plug in a
custom `ByteBufAllocator` into the bootstrap and have it initialize a
custom `ResourceLeakDetector`. Due to these classes mostly being marked
`final` or having private or static methods, a lot of the code had to
be copy-pasted and it's quite ugly.
Modifications:
* I've added a static loader method for the `ResourceLeakDetector` in
`AbstractByteBuf` that tries to instantiate the class passed in via the
`-Dio.netty.customResourceLeakDetector`, otherwise falling back to the
default one.
* I've modified `ResourceLeakDetector` to be non-final and to have the
reporting broken out in to methods that can be overridden.
Result:
You can instrument leaks in your application by just adding something
like the following:
```java
public class InstrumentedResourceLeakDetector<T> extends
ResourceLeakDetector<T> {
@Monitor("InstanceLeakCounter")
private final AtomicInteger instancesLeakCounter;
@Monitor("LeakCounter")
private final AtomicInteger leakCounter;
public InstrumentedResourceLeakDetector(Class<T> resource) {
super(resource);
this.instancesLeakCounter = new AtomicInteger();
this.leakCounter = new AtomicInteger();
}
@Override
protected void reportTracedLeak(String records) {
super.reportTracedLeak(records);
leakCounter.incrementAndGet();
}
@Override
protected void reportUntracedLeak() {
super.reportUntracedLeak();
leakCounter.incrementAndGet();
}
@Override
protected void reportInstancesLeak() {
super.reportInstancesLeak();
instancesLeakCounter.incrementAndGet();
}
}
```
Motivation:
See #82.
Modifications:
- Added `isText` to validate if the given ByteBuf is compliant with the specified charset.
- Optimized for UTF-8 and ASCII. For other cases, `CharsetDecoder.decoder` is used.
Result:
Users can validate ByteBuf with given charset.
Motivation:
If the user uses unsafe direct buffers with no cleaner we can use Unsafe.reallocateMemory(...) as optimization when we need to expand the buffer.
Modifications:
Use Unsafe.relocateMemory(...) in UnpooledUnsafeNoCleanerDirectByteBuf.
Result:
Less expensive expanding of buffers.
Motivation:
Using the Cleaner to release the native memory has a few drawbacks:
- Cleaner.clean() uses static synchronized internally which means it can be a performance bottleneck
- It put more load on the GC
Modifications:
Add new buffer implementations that can be enabled with a system flag as optimizations. In this case no Cleaner is used at all and the user must ensure everything is always released.
Result:
Less performance impact by direct buffers when need to be allocated and released.
Motivation:
Unsafe offers a method to set memory to a specific value. This can be used to implement an optimized version of setZero(...) and writeZero(...)
Modifications:
Add implementation for all Unsafe*ByteBuf implementations.
Result:
Faster setZero(...) and writeZero(...)
Motivation:
At the moment the user is responsible to increase the writer index of the composite buffer when a new component is added. We should add some methods that handle this for the user as this is the most popular usage of the composite buffer.
Modifications:
Add new methods that autoamtically increase the writerIndex when buffers are added.
Result:
Easier usage of CompositeByteBuf.
Motivation:
Some tests in PooledByteBufAllocatorTest are blocking on a CountDownLatch. We should use a timeout on these tests so these will not block forever on a failure.
Modifications:
Add timeout param to @Test annotation
Result:
Have sane timeouts on tests.
Motivation:
DefaultByteBufHolder.equals(...) and hashCode() should be implemented so it works correctly with instances that share the same content.
Modifications:
Add implementations and a unit-test.
Result:
Have correctly working equals(...) and hashCode() method
Motivation:
PooledByteBufAllocatorTest.testNumThreadCachesWithNoDirrectArenas() had a race as it just used LockSupport.parkNanos(). We should better use a CountdownLatch and so be sure we really have init everything.
Modifications:
Replace LockSupport.parkNanos(...) with CountdownLatch usage
Result:
No more race in test.
Motivation:
We called deallocationsHuge.decrement() but it needs to be increment()
Modifications:
Replace decrement() with increment()
Result:
Correct metrics.
Motivation:
When FixedCompositeByteBuf was constructed with new ByteBuf[0] and IndexOutOfboundsException was thrown.
Modifications:
Fix constructor
Result:
No more exception
Motivation:
Some ByteBuf implementations do not override all necessary methods,
which can lead to potentially sub-optimal behavior.
Also, SlicedByteBuf does not perform the range check correctly due to
missing overrides.
Modifications:
- Add missing overrides
- Use unwrap() instead of direct member access in derived buffers for
consistency
- Merge unwrap0() into unwrap() using covariant return type
- Deprecate AbstractDerivedByteBuf and its subtypes, because they were
not meant to be public
Result:
Correctness
Motivation:
ByteBuf.readBytes(...) uses Unpooled.buffer(...) internally which will use a heap ByteBuf and also not able to make use of the allocator which may be pooled. We should better make use of the allocator.
Modifications:
Use the allocator for thenew buffer.
Result:
Take allocator into account when copy bytes.
Motiviation:
Sometimes it is useful to dump the status of the PooledByteBufAllocator and log it. Doing this is currently a bit cumbersome as the user needs to basically iterate through all the metrics and compose the String. we would better provide an easy way to do this.
Modification:
Add dumpStats() method.
Result:
Easier to get a view into the status of the allocator.
Motivation:
PoolChunkList.allocate(...) should return false without the need to walk all the contained PoolChunks when the requested capacity is larger then the capacity that can be allocated out of the PoolChunks in respect to the minUsage() and maxUsage() of the PoolChunkList.
Modifications:
Precompute the maximal capacity that can be allocated out of the PoolChunks that are contained in the PoolChunkList and use this to fast return from the allocate(...) method if an allocation capacity larger then that is requested.
Result:
Faster detection of allocations that can not be handled by the PoolChunkList and so faster allocations in general via the PoolArena.
Motivation:
To better understand how much memory is used by Netty for ByteBufs it is useful to understand how many bytes are currently active (allocated) per PoolArena.
Modifications:
- Add PoolArenaMetric.numActiveBytes()
Result:
The user is able to get better insight into the PooledByteBufAllocator.
Motivation:
To make it easier to understand PoolChunk and PoolArena we should cleanup duplicated code.
Modifications:
- Move reused code into methods
- Use Math.max(...)
Result:
Cleaner code and easier to understand.
Motivation:
When doing a normal allocation in PoolArena we also tried to allocate out of the PoolChunkList that only contains completely full PoolChunks. This makes no sense as these are full anyway so an allocation will never work here and just gives a perf hit as we need to walk the whole list of PoolChunks in the list.
Modifications:
Not try to allocate from PoolChunkList that only contains full PoolChunks
Result:
Faster allocation times when a new PoolChunk must be created.
Motivation:
We should better use Math utilities as these are intrinsics. This is a cleanup for ea3ffb85368ab135087debff003de30aee7d9091.
Modifications:
Use Math utilities.
Result:
Cleaner code and use of intrinsics.
Motivation:
When a PoolChunk needs to get moved to the previous PoolChunkList because of the minUsage / maxUsage constraints we always just moved it one level which is incorrect and so could lead to have PoolChunks in the wrong PoolChunkList (in respect to their minUsage / maxUsage settings). This then could have the effect that PoolChunks are not released / freed in a timely fashion and so.
Modifications:
- Correctly move PoolChunks between PoolChunkLists, which includes moving it multiple "levels".
- Add unit test
Result:
Correctlty move the PoolChunk to PoolChunkList when it is freed, even if its multiple layers.
Motivation:
The PoolChunkList.minUsage() and maxUsage() needs to take special action to translate Integer.MIN_VALUE / MAX_VALUE as these are used internal for tail and head of the linked-list structure.
Modifications:
- Correct the minUsage() and maxUsage() methods.
- Add unit test.
Result:
Correct metrics
Motivation:
Sometimes it is useful to allow to disable the leak detection of buffers if the UnpooledByteBufAllocator is used. This is for example true if the app wants to leak buffers into user code but not want to put the burden on the user to always release the buffer.
Modifications:
Add another constructor to UnpooledByteBufAllocator that allows to completely disable leak-detection for all buffers that are allocator out of the UnpooledByteBufAllocator.
Result:
It's possible to disable leak-detection when the UnpooledByteBufAllocator is used.
Motivation:
We should only increment the metric for the huge / normal allocation after it is done. Also we should only decrement once deallocate.
Modifications:
- Move increment after the allocation.
- Fix deallocation metric and move it after deallocation
Result:
More correct metrics.
Motivation:
PoolThreadCache includes the wrong value when throwing a IllegalArgumentException because of freeSweepAllocationThreshold.
Modifications:
Use the correct value.
Result:
Correct exception message.
Motivation:
The method setBytes creates temporary heap buffer when source buffer is read-only.
But this temporary buffer is not used correctly and may lead to data corruption.
This problem occurs when target buffer is pooled and temporary buffer
arrayOffset() is not zero.
Modifications:
Use correct arrayOffset when calling PlatformDependent.copyMemory.
Unit test was added to test this case.
Result:
Setting buffer content works correctly when target is pooled buffer and source
is read-only ByteBuffer.
Motivation:
We also need to add synchronization when access fields to ensure we see the latest updates.
Modifications:
Add synchronization when read fields that are written concurrently.
Result:
Ensure correct visibility of updated.
Motivation:
We had some double spacing in the methods which should be removed to keep things consistent.
Modifications:
Remove redundant spaces.
Result:
Cleaner / consistent coding style.
Motivation:
My previous commit b88a980482d2ae introduced a flawed unit test,
that executes an assertion in a different thread than the test thread.
If this assertion fails, the test doesn't fail.
Modifications:
Replace the assertion by a proper workaround.
Result:
More correct unit test
Motivation:
Circular assignment of arenas to thread caches can lead to less than optimal
mappings in cases where threads are (frequently) shutdown and started.
Example Scenario:
There are a total of 2 arenas. The first two threads performing an allocation
would lead to the following mapping:
Thread 0 -> Arena 0
Thread 1 -> Arena 1
Now, assume Thread 1 is shut down and another Thread 2 is started. The current
circular assignment algorithm would lead to the following mapping:
Thread 0 -> Arena 0
Thread 2 -> Arena 0
Ideally, we want Thread 2 to use Arena 1 though.
Presumably, this is not much of an issue for most Netty applications that do all
the allocations inside the eventloop, as eventloop threads are seldomly shut down
and restarted. However, applications that only use the netty-buffer package
or implement their own threading model outside the eventloop might suffer from
increased contention. For example, gRPC Java when using the blocking stub
performs some allocations outside the eventloop and within its own thread pool
that is dynamically sized depending on system load.
Modifications:
Implement a linear scan algorithm that assigns a new thread cache to the arena
that currently backs the fewest thread caches.
Result:
Closer to ideal mappings between thread caches and arenas. In order to always
get an ideal mapping, we would have to re-balance the mapping whenever a thread
dies. However, that's difficult because of deallocation.
Motivation:
The statistic counters PoolArena.(allocationsTiny|allocationsSmall) are
not protected by a per arena lock, but by a per size class lock. Thus,
two concurrent allocations of different size (class) could lead to a
race and ultimately to wrong statistics.
Modifications:
Use a thread-safe LongCounter instead of a plain long data type.
Result:
Fewer data races.
Motivation:
See #3321
Modifications:
1. Add CharsetUtil.encoder/decoder() methods
2. Deprecate CharsetUtil.getEncoder/getDecoder() methods
Result:
Users can use new CharsetUtil.encoder/decoder() to specify error actions
Motivation:
Utility methods in ByteBufUtil to writeUtf8 and writeAscii expect a buffer to already be allocated. If the user does not have a buffer allocated they have to know details of the encoding in order to know the size of the buffer to allocate.
Modifications:
- Add writeUtf8 and writeAscii which take a ByteBufAllocator and allocate a ByteBuf of the correct size for the user
Result:
ByteBufUtil methods which are easier to use if the user doesn't already have a ByteBuf.
Motivation:
f750d6e36c80e88fb302c99b5b7413e5649e6738 added support for surrogates in the writeUtf8 conversion. However exceptions are thrown if invalid input is detected, but the JDK (and slow path of writeUtf8) uses a replacement character and does not throw. We should behave the same way.
Modificiations:
- Don't throw in ByteBufUtil.writeUtf8, and instead use a replacement character consistent with the JDK
Result:
ByteBufUtil.writeUtf8 behavior is consistent with the JDK UTF_8 conversion.
Motivation:
We missed to take the byte[] into account when try to access the bytes and so produce a segfault.
Modifications:
Correctly pass the byte[] in.
Result:
No more segfault.
Motivation:
The current interface for CompositeByteBuf.addComponent is not clear under what conditions ownership is transferred when addComponent is called. There should be a well defined behavior so that users can ensure that no leaks occur.
Modifications:
- CompositeByteBuf.addComponent should always assume reference count ownership
Result:
Users that call CompositeByteBuf.addComponent do not have to independently check if the buffer's ownership has been transferred and if not independently release the buffer.
Fixes https://github.com/netty/netty/issues/4760
