Motivation:
We should convert Http2Exceptions that are produced because of STREAM_CLOSED to ClosedChannelException when hand-over to the child channel to make it more consistent with other transports.
Modifications:
- Check if STREAM_CLOSED is used and if so create a new ClosedChannelException (while preserve the original exception as cause) and use it in the child channel
- Ensure STREAM_CLOSED is used in DefaultHttp2RemoteFlowController when writes are failed because of a closed stream.
- Add testcase
Result:
More consistent and correct exception usage.
Motivation:
Each StreamByteDistributor may allow for priority in different ways, but there are certain characteristics which are invalid regardless of the distribution algorithm. We should validate these invalid characteristics at the flow controller level.
Modifications:
- Disallow negative stream IDs from being used. These streams may be accepted by the WeightedFairQueueByteDistributor and cause state for other valid streams to be evicted.
- Improve unit tests to verify limits are enforced.
Result:
Boundary conditions related to the priority parameters are validated more strictly.
Motivation:
We used some deprecated Mockito methods.
Modifications:
- Replace deprecated method usage
- Some cleanup
Result:
No more usage of deprecated Mockito methods. Fixes [#6482].
Motivation:
codec-http2 couples the dependency tree state with the remainder of the stream state (Http2Stream). This makes implementing constraints where stream state and dependency tree state diverge in the RFC challenging. For example the RFC recommends retaining dependency tree state after a stream transitions to closed [1]. Dependency tree state can be exchanged on streams in IDLE. In practice clients may use stream IDs for the purpose of establishing QoS classes and therefore retaining this dependency tree state can be important to client perceived performance. It is difficult to limit the total amount of state we retain when stream state and dependency tree state is combined.
Modifications:
- Remove dependency tree, priority, and weight related items from public facing Http2Connection and Http2Stream APIs. This information is optional to track and depends on the flow controller implementation.
- Move all dependency tree, priority, and weight related code from DefaultHttp2Connection to WeightedFairQueueByteDistributor. This is currently the only place which cares about priority. We can pull out the dependency tree related code in the future if it is generally useful to expose for other implementations.
- DefaultHttp2Connection should explicitly limit the number of reserved streams now that IDLE streams are no longer created.
Result:
More compliant with the HTTP/2 RFC.
Fixes https://github.com/netty/netty/issues/6206.
[1] https://tools.ietf.org/html/rfc7540#section-5.3.4
Motivation:
Performing a server upgrade with a new initial flow control window will cause an NPE in the DefaultHttp2RemoteFlowController. This is due to the fact that the monitor does not check whether or not the channel is writable.
Modifications:
Added a check for channel writability before calling `writePendingBytes`. Also fixed a unit test that was supposed to be testing this :).
Result:
Fixes#5301
Motivation:
The DefaultHttp2Conneciton.close method accounts for active streams being iterated and attempts to avoid reentrant modifications of the underlying stream map by using iterators to remove from the stream map. However there are a few issues:
- While iterating over the stream map we don't prevent iterations over the active stream collection
- Removing a single stream may actually remove > 1 streams due to closed non-leaf streams being preserved in the priority tree which may result in NPE
Preserving closed non-leaf streams in the priority tree is no longer necessary with our current allocation algorithms, and so this feature (and related complexity) can be removed.
Modifications:
- DefaultHttp2Connection.close should prevent others from iterating over the active streams and reentrant modification scenarios which may result from this
- DefaultHttp2Connection should not keep closed stream in the priority tree
- Remove all associated code in DefaultHttp2RemoteFlowController which accounts for this case including the ReducedState object
- This includes fixing writability changes which depended on ReducedState
- Update unit tests
Result:
Fixes https://github.com/netty/netty/issues/5198
Motivation:
DefaultHttp2RemoteFlowController does not correctly account for the padding in the event frames are merged. This causes the internal stat of DefaultHttp2RemoteFlowController to become corrupt and can result in attempting to write frames when there are none.
Modifications:
- Update DefaultHttp2RemoteFlowController to account for frame sizes not necessarily adding together.
Result:
DefaultHttp2RemoteFlowController internal state does not become corrupt when padding is present.
Fixes https://github.com/netty/netty/issues/4573
Motivation:
RemoteFlowController.streamWritten is not currently required. We should remove it to keep interfaces minimal.
Modifications:
- Remove RemoteFlowController.streamWritten
Result:
1 Less method in RemoteFlowController interface.
Fixes https://github.com/netty/netty/issues/4600
Motivation:
DefaultHttp2RemoteFlowController.ListenerWritabilityMonitor no longer reliably detects when a stream's writability change occurs.
Modifications:
- Ensure writiability is reliabily reported by DefaultHttp2RemoteFlowController.ListenerWritabilityMonitor
- Fix infinite loop issue (https://github.com/netty/netty/issues/4588) detected when consolidating unit tests
Result:
Reliable stream writability change notification, and 1 less infinite loop in UniformStreamByteDistributor.
Fixes https://github.com/netty/netty/issues/4587
Motivation:
The `DefaultHttp2RemoteFlowController` does not correctly determine `hasFrame` when updating the stream state for the distributor. Adding a check to enforce `hasFrame` when `streamableBytes > 0` causes several test failures.
Modifications:
Modified `DefaultHttp2RemoteFlowController` to simplify the writing logic and to correct the bookkeeping for `hasFrame`.
Result:
The distributors are always called with valid arguments.
Motivation:
PriorityStreamByteDistributor saves exception state and attempts to reset state. This could be simplified by just throwing a connection error and closing the connection. PriorityStreamByteDistributor also does not handle or detect re-entry in the distribute method.
Motivation:
- PriorityStreamByteDistributor propagate an INTERNAL_ERROR if an exception occurs during writing
- PriorityStreamByteDistributor to handle re-entry on the write method
Result:
PriorityStreamByteDistributor exception code state simplified, and re-entry is detected.
Motivation:
For implementations that want to manage flow control down to the stream level it is useful to be notified when stream writability changes.
Modifications:
- Add writabilityChanged to Http2RemoteFlowController.Listener
- Add isWritable to Http2RemoteFlowController
Result:
The Http2RemoteFlowController provides notification when writability of a stream changes.
Motivation:
The DefaultHttp2RemoteFlowController has become very large and is getting difficult to understand and maintain. It is also desirable for some applications to be able to disable the priority algorithm altogether for performance reasons.
Modifications:
Abstract the stream byte assignment logic (renamed allocation->assignment for clarity) behind an interface `StreamByteAssigner` with a single implementation `PriorityStreamByteAssigner`.
Result:
Goes some way towards supporting #4246
Motivation:
DefaultHttp2RemoteFlowController's allocation algorithm may not allocate all bytes that are available in the connection window. If the 'fair share' based upon weight is not fully used by sibling nodes it was not correctly re-distributed to other sibilings which may be able to utilize part / all of that share.
Modifications:
- Add a unit test which demonstrates the issue.
- Modify the allocation algorithm to ensure all available bytes are allocated.
Result:
Fixes https://github.com/netty/netty/issues/4266
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:
It is currently assumed that all usages of the HTTP/2 codec will be from the same event loop context. If the methods are used outside of the assumed thread context then unexpected behavior is observed. This assumption should be more clearly communicated and enforced in key areas.
Modifications:
- The flow controller interfaces have assert statements and updated javadocs indicating the assumptions.
Result:
Interfaces more clearly indicate thread context limitations.
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 Http2FrameListener requires that the Http2FrameReader accumulate ByteBuf objects. There is currently no way to limit the amount of bytes that is accumulated.
Motiviation:
- DefaultHttp2FrameReader supports maxHeaderSize which will fail fast as soon as the maximum size is exceeded.
- DefaultHttp2HeadersDecoder will respect the return value of endHeaderBlock() and fail if the max size is exceeded.
Result:
Frames which carry header data now respect a maximum number of bytes that can be accumulated.
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:
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:
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:
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:
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:
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:
- 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:
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:
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:
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
