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:
While forward porting https://github.com/netty/netty/pull/3579 there were a few areas that had not been previously back ported.
Modifications:
Backport the missed areas to ensure consistency.
Result:
More consistent 4.1 and master branches.
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.
Motivation:
The Http2FrameLogger is currently using the internal logging classes. We should change this so that it's using the public classes and then converts internally.
Modifications:
Modified Http2FrameLogger and the examples to use the public LogLevel class.
Result:
Fixes#2512
Motivation:
The current documentation for Endpoint methods referring to concurrent streams and the SETTINGS_MAX_CONCURRENT_STREAMS setting are a bit confusing.
Modifications:
Renamed a few of the methods and added more clear documentation.
Result:
Fixes#3451
Motivation:
There are two writeRstStream methods in the DefaultHttp2ConnectionEncoder.
One of the two is neither used nor part of the Http2FrameWriter interface.
Modifications:
Delete the method.
Result:
Fewer lines of dead code.
Motivation:
For every write of a flow controlled frame (HEADERS, DATA) we are allocating
a Frame object that is not necessary anymore as it does not maintain any
state, besides the payload.
Modifications:
Remove the Frame class and directly add the payload to the pending write queue.
Result:
One few object allocation per write of a flow controlled frame.
Motivation:
The logger was always performing a hex dump of the ByteBufs regarless whether or not the log would take place.
Modifications:
Fixed the logger to avoid serializing the ByteBufs and calling the varargs method if logging is not enabled.
Result:
The loggers should run MUCH faster when disabled.
Motivation:
If HEADERS or DATA frames are pending due to a too small flow control
window, a frame with the END_STREAM flag set will wrongfully cancel
all pending frames (including itself).
Also see grpc/grpc-java#145
Modifications:
The transition of the stream state to CLOSE / HALF_CLOSE due to a
set END_STREAM flag is delayed until the frame with the flag is
actually written to the Channel.
Result:
Flow control works correctly. Frames with END_STREAM flag will no
longer cancel their preceding frames.
Motivation:
HttpToHttp2ConnectionHandlerTest was accidentally modified with a
debugging value for WAIT_TIME_SECONDS.
Modifications:
Reverted the change.
Result:
original wait time restored.
Motivation:
The Http2DefaultFrameWriter copies all contents into a buffer (or uses a CompositeBuffer in 1 case) and then writes that buffer to the socket. There is an opportunity to avoid the copy operations and write directly to the socket.
Modifications:
- Http2DefaultFrameWriter should avoid copy operations where possible.
- The Http2FrameWriter interface should be clarified to indicate that ByteBuf objects will be released.
Result:
Hopefully less allocation/copy leads to memory and throughput performance benefit.
Motivation:
Http2Stream has several methods that provide state information. We need
to simplify how state is used and consolidate as many of these fields as
possible.
Modifications:
Since we already have a concept of a stream being active or inactive,
I'm now separating the deactivation of a stream from the act of closing
it. The reason for this is the case of sending a frame with
endOfStream=true. In this case we want to close the stream immediately
in order to disallow further writing, but we don't want to mark the
stream as inactive until the write has completed since the inactive
event triggers the flow controller to cancel any pending writes on the
stream.
With deactivation separated out, we are able to eliminate most of the
additional state methods with the exception of `isResetSent`. This is
still required because we need to ignore inbound frames in this case (as
per the spec), since the remote endpoint may not yet know that the
stream has been closed.
Result:
Fixes#3382
Motivation:
Previously flow-controller had to know the implementation details of each frame type in order to write it correctly. That concern is more correctly handled by the encoder. By encapsulating the payload types to be flow-controlled it will be easier to add support for extension types later. This change also fixes#3353.
Modifications:
Add interface FlowControlled which is now delivered to flow-controller.
Implement this interface for HEADERS and DATA
Refactor and improve tests for flow-control.
Result:
Flow control semantics are more cleanly separated for data encoding and implementation is simpler overall.
Motivation:
A downstream consumer of Netty failed as emitting zero-length http2 data frames in a unit test resulted in assertion errors in Http2LocalFlowController. Since zero-length frames are valid, an assertion that http2 data frame length must be positive is invalid.
Modifications:
Assertions of data length in Http2LocalFlowController now permit zero.
Result:
Those running netty with assertions on can now emit zero length http2 data frames.
Motivation:
HTTP/2 codec was implemented in master branch.
Since, master is not yet stable and will be some time before it gets released, backporting it to 4.1, enables people to use the codec with a stable netty version.
Modification:
The code has been copied from master branch as is, with minor modifications to suit the `ChannelHandler` API in 4.x.
Apart from that change, there are two backward incompatible API changes included, namely,
- Added an abstract method:
`public abstract Map.Entry<CharSequence, CharSequence> forEachEntry(EntryVisitor<CharSequence> visitor)
throws Exception;`
to `HttpHeaders` and implemented the same in `DefaultHttpHeaders` as a delegate to the internal `TextHeader` instance.
- Added a method:
`FullHttpMessage copy(ByteBuf newContent);`
in `FullHttpMessage` with the implementations copied from relevant places in the master branch.
- Added missing abstract method related to setting/adding short values to `HttpHeaders`
Result:
HTTP/2 codec can be used with netty 4.1
