Motivation:
ByteToMessageDecoder may call decode after channelInactive is called. This will lead to a NPE.
Modifications:
- Call super.channelInactive() before we process the event in Http2ConnectionHandler
Result:
No more NPE in decode.
Motivation:
If any streams are still active the graceful shutdown code will wait until they are all closed before the connection is closed. In some situations this event may never occur, and thus a timeout should be supported so the socket can be closed even if all streams haven't been closed.
Modifications:
- Add a configurable timeout for when the graceful shutdown process is attempted.
- Update unit tests to be faster, and use this graceful timeout
Result:
Local endpoint can protect from local or remote issues which prevent the channel from being closed during the graceful shutdown process.
Motivation:
The Http2ConnectionHandler was writing pending bytes, but was not flushing. This may result in deadlock.
Modifications:
- Http2ConnectionHandler must writePendingBytes and also flush.
Result:
Data is now flushed after writabilityChange writes more data to underlying layers.
Motivation:
See #3783
Modifications:
- The DefaultHttp2RemoteFlowController should use Channel.isWritable() before attempting to do any write operations.
- The Flow controller methods should no longer take ChannelHandlerContext. The concept of flow control is tied to a connection and we do not support 1 flow controller keeping track of multiple ChannelHandlerContext.
Result:
Writes are delayed until isWritable() is true. Flow controller interface methods are more clear as to ChannelHandlerContext restrictions.
Motivation:
The problem is described in https://github.com/grpc/grpc-java/issues/605. Basically, when using `StreamBufferingEncoder` there is a chance of creating zombie streams that never get closed.
Modifications:
Change `Http2ConnectionHandler`'s `channelInactive` handling logic to shutdown the encoder/decoder before shutting down the active streams.
Result:
Fixes https://github.com/grpc/grpc-java/issues/605
Motivation:
Http2ConnectionHandler missed to forward channelReadComplete(...) events.
Modifications:
Ensure we notify the next handler in the pipeline via ctx.fireChannelReadComplete().
Result:
Correctly forwarding of event.
Motivation:
Coalescing many small writes into a larger DATA frame reduces framing overheads on the wire and reduces the number of calls to Http2FrameListeners on the remote side.
Delaying the write of WINDOW_UPDATE until flush allows for more consumed bytes to be returned as the aggregate of consumed bytes is returned and not the amount consumed when the threshold was crossed.
Modifications:
- Remote flow controller no longer immediately writes bytes when a flow-controlled payload is enqueued. Sequential data payloads are now merged into a single CompositeByteBuf which are written when 'writePendingBytes' is called.
- Listener added to remote flow-controller which observes written bytes per stream.
- Local flow-controller no longer immediately writes WINDOW_UPDATE when the ratio threshold is crossed. Now an explicit call to 'writeWindowUpdates' triggers the WINDOW_UPDATE for all streams who's ratio is exceeded at that time. This results in
fewer window updates being sent and more bytes being returned.
- Http2ConnectionHandler.flush triggers 'writeWindowUpdates' on the local flow-controller followed by 'writePendingBytes' on the remote flow-controller so WINDOW_UPDATES preceed DATA frames on the wire.
Result:
- Better throughput for writing many small DATA chunks followed by a flush, saving 9-bytes per coalesced frame.
- Fewer WINDOW_UPDATES being written and more flow-control bytes returned to remote side more quickly, thereby improving throughput.
Motivation:
Bootstrap of the HTTP/2 can take a lot of paths and a lot of things can go wrong in the initial handshakes leading up to establishment of HTTP/2 between client and server. There have been many times where handshakes have failed silently, leading to very cryptic errors that are hard to debug.
Modifications:
Changed the HTTP/2 handler and decoder to ensure that the very first data on the wire (WRT HTTP/2) is SETTINGS/preface+SETTINGS. When this is not the case, a connection error is thrown with the bytes that were found instead.
Result:
Fixes#3880
Motiviation:
The connection handler stream close operation is unconditionally adding a listener object to a future. We may not have to add a listener at all because the future has already been completed.
Modifications:
- If the future is done, directly invoke the logic without creating/adding a new listener.
Result:
No need to create/add listener if the future is already done in close logic.
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.
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:
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:
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.
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:
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 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:
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.
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 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 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 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:
- 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 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:
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:
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