Motivation:
There is currently no good way to configure the initial SETTINGS frame. The individual settings can be configured on the various components, but doing this bypasses the proper setting update logic in the encoder.
Modifications:
Updated Http2ConnectionHandler to optionally take initial settings in the constructor. If not provided, it will default to current behavior.
Result:
Easy manual configuration of initial settings.
Motivation:
The Http2OutboundFrameLogger logs all PING frames as not acks.
Modifications:
Changed the logger to correctly log PING acks.
Result:
PING acks are logged correctly.
Motiviation:
The Http2ConnectionHandler is incrementing the reference count in the goAway method for the debugData buffer after it has already been sent and maybe consumed. This may result in an IllegalRefCountException to be thrown. The unit tests also encounter buffer leaks because they have not been updated to invoke the listener which releases the buffer in the goAway method.
Modifications:
- The retain() call should be before the frameWriter().writeGoAway(...) call
- The unit tests which call goAway must also invoke the operationComplete(..) method for the listener.
Result:
No IllegalRefCountException. Less buffer leaks in tests.
Motivation:
If headers are sent on a stream that does not yet exist and the END_STREAM flag is set we will send a RST_STREAM frame. We should send the HEADERS frame and no RST_STREAM.
Modifications:
DefaultHttp2RemoteFlowController should allow frames to be sent if stream is created in the 'half closed (local)' state.
Result:
We can send HEADERS frame with the END_STREAM flag sent without sending a RST_STREAM frame.
Motivation:
There were a few outstanding comments that were left unaddressed after committing the changes for #3749.
Modifications:
Changes to Http2ConnectionHandler.goAway():
- Retaining the debugData buffer, rather than always converting it to a string immediately.
- Changing log level for sending a GOAWAY with error to debug.
Result:
Remaining comments from #3749 are addressed.
Motivation:
Currently the graceful shutdown of the HTTP/2 connection waits until there are no active streams. There may be use cases that buffer stream creation (due to limits imposed by MAX_CONCURRENT_STREAMS), in which case they may still want those streams to complete before closing.
Modifications:
Added a isGracefulShutdownComplete method to Http2ConnectionHandler, which can be overridden by a subclass.
Result:
Graceful shutdown logic can be overridden.
Motivation:
If the client closes, a GOWAY is sent with a lastKnownStream of zero (since the remote side never created a stream). If there is still an exchange in progress, inbound frames for streams created by the client will be ignored because our ignore logic doesn't check to see if the stream was created by the remote endpoint. Frames for streams created by the local endpoint should continue to come through after sending GOAWAY.
Modifications:
Changed the decoder's streamCreatedAfterGoAwaySent logic to properly ensure that the stream was created remotely.
Result:
We now propertly process frames received after sending GOAWAY.
Motivation:
The isDone method is currently broken in the aggregator because the doneAllocatingPromises accidentally calls the overridden version of setSuccess, rather than calling the base class version. This causes the base class's version to never be called since allowNotificationEvent will evaluate to false. This means that setSuccess0 will never be set, resulting in isDone always returning false.
Modifications:
Changed setSuccess() to call the base class when appropriate, regardless of the result of allowNotificationEvent.
Result:
isDone now behaves properly for the promise aggregator.
Motivation:
Allow users of HTTP2 to control when flushes occur so they can optimize network writes.
Modifications:
Removed explicit calls to flush in encoder, decoder & flow-controller
Connection handler now calls flush on read-complete to enable batching writes in response to reads
Result:
Much less flushing occurs for normal HTTP2 request and response patterns.
Motiviation:
There are a few spots in the HTTP/2 codec where warnings were generated and can be avoided.
Modifications:
Clean up the cause of the warnings.
Result:
Less warnings.
Motivation:
The Http2ConnectionHandler incorrectly doesn't propagate channelActive and channelInactive events and thus breaks the pipeline
for other ChannelHandler.
Modification:
- Add calls to super.channelActive() and super.channelInactive().
- Remove unused methods.
Result:
- Http2ConnectionHandler can be used with other ChannelHandlers.
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[].
Motivation:
Streams currently maintain a hash map of user-defined properties, which has been shown to add significant memory overhead as well as being a performance bottleneck for lookup of frequently used properties.
Modifications:
Modifying the connection/stream to use an array as the storage of user-defined properties, indexed by the class that identifies the index into the array where the property is stored.
Result:
Stream processing performance should be improved.
Motivation:
Currently we allocate the full amount of state for each stream as soon as the stream is created, and keep that state until the stream is GC. The full set of state is only needed when the stream can support flow controlled frames. There is an opportunity to reduce the required amount of memory, and make memory eligible for GC sooner by only allocating what is necessary for flow control stream state.
Modifications:
Introduce objects which require 'less' state for local/remote flow control stream state.
Use these new objects when streams have been created but will not transition out of idle AND when streams are no longer eligible for flow controlled frame transfer but still must persist in the priority tree.
Result:
Memory allocations are reduced to what is actually needed, and memory is made eligible for GC potentially sooner.
Motivation:
The recent PR that discarded the Http2StreamRemovalPolicy causes connection errors when receiving a frame for a stream that no longer exists. We should ignore these frames if we think there's a chance that the stream has existed previously
Modifications:
Modified the Http2Connection interface to provide a `streamMayHaveExisted` method. Also removed the requireStream() method to identify all of the places in the code that need to be updated.
Modified the encoder and decoder to properly handle cases where a stream may have existed but no longer does.
Result:
Fixes#3643
Motivation:
The current local flow controller does not guarantee that unconsumed bytes for a closed stream will be restored to the connection window. This may lead to degradation of the connection window over time.
Modifications:
Modified DefaultHttp2LocalFlowController to guarantee that any unconsumed bytes are returned to the connection window as soon as the stream is closed. We also immediately consume any bytes when receiving DATA for a closed stream.
Result:
Fixes#3668
Motivation:
Flow control is a required part of the HTTP/2 specification but it is currently structured more like an optional item. It must be accessed through the property map which is time consuming and does not represent its required nature. This access pattern does not give any insight into flow control outside of the codec (or flow controller implementation).
Modifications:
1. Create a read only public interface for LocalFlowState and RemoteFlowState.
2. Add a LocalFlowState localFlowState(); and RemoteFlowState remoteFlowState(); to Http2Stream.
Result:
Flow control is not part of the Http2Stream interface. This clarifies its responsibility and logical relationship to other interfaces. The flow controller no longer must be acquired though a map lookup.
Motivation:
If an exclusive dependency change stream B should be an exclusive dependency of stream A is requested and stream B is already a child of stream A...then we will add B to B's own children map and create a circular link in the priority tree. This leads to an infinite recursive loop and a stack overflow exception.
Modifications:
-when removeAllChildren is called it should not remove the exclusive dependency.
-unit test to ensure this case is covered.
Result:
No more circular link in the priority tree.
Motivation:
The usage and code within AsciiString has exceeded the original design scope for this class. Its usage as a binary string is confusing and on the verge of violating interface assumptions in some spots.
Modifications:
- ByteString will be created as a base class to AsciiString. All of the generic byte handling processing will live in ByteString and all the special character encoding will live in AsciiString.
Results:
The AsciiString interface will be clarified. Users of AsciiString can now be clear of the limitations the class imposes while users of the ByteString class don't have to live with those limitations.
Motivation:
Due to a recent flurry of cleanup and fixes, we no longer need the stream removal policy to protect against recently removed streams. We should get rid of it.
Modifications:
Removed Http2StreamRemovalPolicy and everywhere it's used.
Result:
Fixes#3448
Motivation:
The DefaultHttp2Connection is not checking for RuntimeExceptions when invoking Http2Connection.Listener methods. This is a problem for a few reasons: 1. The state of DefaultHttp2Connection will be corrupted if a listener throws a RuntimeException. 2. If the first listener throws then no other listeners will be notified, which may further corrupt state that is updated as a result of listeners being notified.
Modifications:
- Document that RuntimeExceptions are not supported for Http2Connection.Listener methods, and will be logged as an error.
- Update DefaultHttp2Connection to handle and exception for each listener that is notified, and be sure that 1 listener throwing an exception does not prevent others from being notified.
Result:
More robust DefaultHttp2Connection.
Motivation:
Now that we have a CharObjectHashMap, we should change Http2Settings to use it.
Modifications:
Changed Http2Settings to extend CharObjectHashMap rather than IntObjectHashMap.
Result:
Http2Settings uses less memory to store keys.
Motivation:
We've removed access to the activeStreams collection, we should do the same for the children of a stream to provide a consistent interface.
Modifications:
Moved Http2StreamVisitor to a top-level interface. Removed unnecessary child operations from the Http2Stream interface so that we no longer require a map structure.
Result:
Cleaner and more consistent interface for iterating over child streams.
Motivation:
The Http2Connection interface exposes an activeStreams() method which allows direct iteration over the underlying collection. There are a few places that make copies of this collection to avoid modification while iterating, and a few places that do not make copies. The copy operation can be expensive on hot code paths and also we are not consistently iterating over the activeStreams collection.
Modifications:
- The Http2Connection interface should reduce the exposure of the underlying collection and just expose what is necessary for the interface to function. This is just a means to iterate over the collection.
- The DefaultHttp2Connection should use this new interface and protect it's internal state while iteration is occurring.
Result:
Reduction in surface area of the Http2Connection interface. Consistent iteration of the set of active streams. Concurrent modification exceptions are handled in 1 encapsulated spot.
Motivation:
1) The current implementation doesn't allow for HEADERS, DATA, PING, PRIORITY and SETTINGS
frames to be sent after GOAWAY.
2) When receiving or sending a GOAWAY frame, all streams with ids greater than the lastStreamId
of the GOAWAY frame should be closed. That's not happening.
Modifications:
1) Allow sending of HEADERS and DATA frames after GOAWAY for streams with ids < lastStreamId.
2) Always allow sending PING, PRIORITY AND SETTINGS frames.
3) Allow sending multiple GOAWAY frames with decreasing lastStreamIds.
4) After receiving or sending a GOAWAY frame, close all streams with ids > lastStreamId.
Result:
The GOAWAY handling is more correct.
Motivation:
There are methods to manipulate the prioritzable count for streams which have the '0' postfix which are designed to be used during recursion. However these methods are calling out to an external method without the '0' during the recursive process. This is doing uneccessary conditional checks during recursion.
Modifications:
Change the decrementPrioritizableForTree to decrementPrioritizableForTree0 while in recursive method.
Change the incrementPrioritizableForTree to incrementPrioritizableForTree0 while in recursive method.
Result:
Less overhead during recursive calls.
Motiviation:
The interface provided by Http2LifecycleManager is not clear as to how the writeXXX methods should behave. The implementation of this interface from the Http2ConnectionHandler's perspecitve is unclear what writeXXX means in this context.
Modifications:
- Method names in Http2LifecycleManager and Http2ConnectionHandler should be renamed and comments should clarify the interfaces.
Results:
Http2LifecycleManager is more clear and Http2ConnectionHandler's implementation makes sense w.r.t to return values.
Motivation:
The HTTP/2 headers code should be using binary string (currently AsciiString) objects instead of String objects. The DefaultHttp2HeadersEncoder was still using String for sensitiveHeaders.
Modifications:
- Remove the usage of String from DefaultHttp2HeadersEncoder.
- Introduce an interface to determine if a header name/value is sensitive or not to 1. prevent necessarily creating/copying sets. 2. Allow the name/value to be considered when checking if sensitive.
Result:
No more String in DefaultHttp2HeadersEncoder and less required set creation/operations.
Motivation:
The spec requires that a RST_STREAM received on an IDLE stream results in a connection error. This is not happening.
Modifications:
Check for this condition when a RST_STREAM is received in DefaultHttp2ConnectionDecoder.
Result:
More spec compliant. Fixes https://github.com/netty/netty/issues/3573.
Motivation:
The DefaultHttp2ConnectionDecoder has the setPriority call after the Http2FrameListener is notified of the change. The setPriority call has additional verification logic and may even create the dependency stream and so it must be before the Http2FrameListener is notified.
Modifications:
The DefaultHttp2ConnectionDecoder should treat the setPriority call in the same for the HEADERS and PRIORITY frame (call it before notifying the listener).
Result:
Http2FrameListener should see correct state when a HEADERS frame has a stream dependency that has not yet been created yet. Fixes https://github.com/netty/netty/issues/3572.
Motivation:
We are allocating a hash map for every HTTP2 Stream to store it's children.
Most streams are leafs in the priority tree and don't have children.
Modification:
- Only allocate children when we actually use them.
- Make EmptyIntObjectMap not throw a UnsupportedOperationException on remove, but return null instead (as is stated in it's javadoc).
Result:
Fewer unnecessary allocations.
Motivation:
In a simple load test that creates and closes several 10k streams per second
I have seen Iterator objects using roughly 1.6% of the total committed heap.
Modifications:
Use an ArrayList instead of a LinkedHashSet to store the connection listeners.
That way we can iterate over the list without creating an iterator every time.
Result:
Zero Iterator allocations due to notifying connection listeners.
Motivation:
The Http2Settings class currently disallows setting non-standard settings, which violates the spec.
Modifications:
Updated Http2Settings to permit arbitrary settings. Also adjusting the default initial capacity to allow setting all of the standard settings without reallocation.
Result:
Fixes#3560
Motivation:
The HTTP/2 specification allows for closed (and streams in any state) to exist in the priority tree. The current code removes streams from the priority tree as soon as they are closed (subject to the removal policy). This may lead to undesired distribution of resources from the peer's perspective.
Modifications:
- We should only remove streams from the priority tree when they have no descendant streams in a viable state.
- We should track when tree edges change or nodes are removed if inviable nodes can then be removed.
Result:
Priority tree doesn't remove closed streams until descendant are all closed, or there are no descendants.
Motivation:
We're currently using Math.ceil which isn't necessary. We should exchange for a lighter weight operation.
Modifications:
Changing the logic to just ensure that we allocate at least one byte to the child rather than always performing a ceil.
Result:
Slight performance improvement in the priority algorithm.
Motivation:
The Connection.Listener GOAWAY event handler currently provides no additional information, requiring applications to hack in other ways to get at the error code and debug message.
Modifications:
Modified the Connection.Listener interface to pass on the error code and message that triggered the GOAWAY.
Result:
Application can now use Connection.Listener for all GOAWAY processing.
Motivation:
It currently takes a builder for the encoder and decoder, which makes it difficult to decorate them.
Modifications:
Removed the builders from the interfaces entirely. Left the builder for the decoder impl but removed it from the encoder since it's constructor only takes 2 parameters. Also added decorator base classes for the encoder and decoder and made the CompressorHttp2ConnectionEncoder extend the decorator.
Result:
Fixes#3530
Motivation:
The DefaultHttp2RemoteFlowController's priority algorithm doesn't really need to sort the children by weight since it already fairly distributes data based on weight.
Modifications:
Removing the sorting in the priority algorithm and updating one test to allow a small bit of variability in the results.
Result:
Slight improvement on the performance of the priority algorithm.
Motivation:
The encoder/decoder currently do not handle streams which have previously existed but no longer exist because they were closed. The specification requires supporting this.
Modifications:
- encoder/decoder should tolerate the frame or the dependent frame not existing in the streams map due to the fact that it may have previously existed.
Result:
encoder/decoder are more compliant with the specification.
Motivation:
The DefaultHttp2ConnectionDecoder class is calling verifyPrefaceReceived() for almost every frame event at all times.
The Http2ConnectionHandler class is calling readClientPrefaceString() on every decode event.
Modifications:
- DefaultHttp2ConnectionDecoder should not have to continuously call verifyPrefaceReceived() because it transitions boolean state 1 time for each connection.
- Http2ConnectionHandler should not have to continuously call readClientPrefaceString() because it transitions boolean state 1 time for each connection.
Result:
- Less conditional checks for the mainstream usage of the connection.
Motivation:
The current DefaultHttp2RemoteFlowController's writePendingBytes currently operates in 2 passes. The first allocates bytes and optionally writes some frames. The second pass just loops across all active streams and writes all remaining bytes.
If streams can be removed/added as a side effect of writing (EOS or error) then we need to take more care when the write actually occurs. Moving all of the writes to the second loop (across active streams) is simpler since we can just make a copy of the list and not worry about any restructuring of the priority tree that may result.
Modifications:
Modified DefaultHttp2RemoteFlowController.writePendingBytes to only allocate bytes on the first pass and then write any allocated bytes on the second pass.
Result:
Side effects resulting from writing should no longer impact the flow control algorithm.
Motivation:
A microbenchmark will be useful to get a baseline for performance.
Modifications:
- Introduce a new microbenchmark which tests the Http2DefaultFrameWriter.
- Allow benchmarks to run without thread context switching between JMH and Netty.
Result:
Microbenchmark exists to test performance.
Motivation:
The Http2ConnectionHandler writeRstStream method allows RST_STREAM frames to be sent when we do not know about the stream and after a RST_STREAM frame has already been sent. This may lead to sending frames when we should not according to the HTTP/2 spec. There is also the potential to notify the closeListener multiple times if the closeStream method is called multiple times.
Modifications:
- Prevent RST_STREAM from being sent if we don't know about the stream, or if we already sent the RST_STREAM.
- Prevent the closeListener from being notified multiple times.
Result:
More robust writeRstStream logic in boundary conditions.
Motivation:
There was a new draft for HTTP/2. We should support the new draft.
Modifications:
- Review the HTTP/2 draft 17 specification, and update code to reflect changes.
Result:
Support for HTTP/2 draft 17.
Motivation:
- In FlowState.write(...) we are currently swalloing an exception.
- In my previous commit I introduced a compiler warning by not making
a local variabe final.
Modifications:
- Have FlowState.cancel() take a Throwable.
- Make the variable final.
Result:
No more swallowed exceptions and warnings.
Motivation:
- The encoder and decoder should be closed right after the handler releases its resources.
- The clientPrefaceString is allocated in the constructor but releases in handlerRemoved.
If the handler is never added to the pipeline, the clientPrefaceString will never be
released.
Modifications:
- Call encoder.close() and decoder.close() on channelInactive.
- Release the clientPrefaceString on handlerRemoved.
Result:
- The encoder and decoder get closed right after the handler's resources are freed.
- It's easier to verify that the clientPrefaceString will also get released.
