**Motivation:**
When I was previously working on a project using Netty's HTTP/2 support, I used the newer frames approach but I struggled to find any good examples or documentation online. I did, however, see a few people ask the same (or similar) questions as me on StackOverflow and a couple of older Netty Github issues.
Reading issue [9733](https://github.com/netty/netty/issues/9733) therefore prompted me to pull together a few bits of code into this HTTP/2 frame client example.
**Modification:**
Populated the previously-empty `example/src/main/java/io/netty/example/http2/helloworld/frame/client/` folder with a HTTP/2 frame client example.
**Result:**
Gives a clear example of how the newer HTTP/2 support can be used for Netty clients.
Motivation:
java.io.File.listFiles() may return null and cause a unexpected NPE.
Modification:
Extract a local variable from the return value of File.listFiles() and do a null check.
Result:
Fix the potential NPE.
Motivation:
Since "Http2ClientInitializer" creates a new SSLContext Handler without specifying Host, Netty does not add SNI Extension in TLS Client Hello request and the request fails if the server uses SNI to establish TLS Connection.
Modification:
Specified Host while creating a new SSLContext Handler in "Http2ClientInitializer".
Result:
Netty adds SNI Extension of the Host Specified in new SSLContext Handler and sends it with TLS Client Hello request.
Fixes#9815.
Motivation:
After fix#9377 some websocket examples work incorrect
Modification:
Replace `Unpooled.EMPTY_BUFFER` to `ctx.alloc().buffer(0)` for responses with possible content
Result:
Examples work
Motivation:
In many places Netty uses Unpooled.buffer(0) while should use EMPTY_BUFFER. We can't change this due to back compatibility in the constructors but can use Unpooled.EMPTY_BUFFER in some cases to ensure we not allocate at all. In others we can directly use the allocator either from the Channel / ChannelHandlerContext or the request / response.
Modification:
- Use Unpooled.EMPTY_BUFFER where possible
- Use allocator where possible
Result:
Fixes#9345 for websockets and http package
Motivation:
Recently I'm going to build MQTT broker and client based on Netty. I had MQTT encoder and decoder founded, while no basic examples. So I'm going to share my simple heartBeat MQTT broker and client as an example.
Modification:
New MQTT heartBeat example under io.netty.example/mqtt/heartBeat/.
Result:
Client would send CONNECT and PINGREQ(heartBeat message).
- CONNECT: once channel active
- PINGREQ: once IdleStateEvent triggered, which is 20 seconds in this example
Client would discard all messages it received.
MQTT broker could handle CONNECT, PINGREQ and DISCONNECT messages.
- CONNECT: send CONNACK back
- PINGREQ: send PINGRESP back
- DISCONNECT: close the channel
Broker would close the channel if 2 heartBeat lost, which set to 45 seconds in this example.
Motivation:
Some methods that either override others or are implemented as part of implementation an interface did miss the `@Override` annotation
Modifications:
Add missing `@Override`s
Result:
Code cleanup
Motivation:
In the past we had the following class hierarchy:
Http2ConnectionHandler --- Http2FrameCodec -- Http2MultiplexCodec
This hierarchy makes it impossible to plug in any code that would like to act on Http2Frame and Http2StreamFrame which can be quite useful for various situations (like metrics, logging etc). Beside this it also made the implementtion very hacky. To allow easier maintainance and also allow more flexible costumizations we should split Http2MultiplexCodec and Http2FrameCode.
Modifications:
- Introduce Http2MultiplexHandler (which is a replacement for Http2MultiplexCodec when used together with Http2FrameCodec)
- Mark Http2MultiplexCodecBuilder and Http2MultiplexCodec as deprecated. People should use Http2FrameCodecBuilder / Http2FrameCodec together with Http2MultiplexHandlder in the future
- Adjust / Add tests
- Adjust examples
Result:
More flexible usage possible and less hacky / coupled implementation for http2 multiplexing
Motivation:
The io.netty.example.http2.helloworld.client.Http2Client example should work in the h2c (HTTP2 cleartext - non-TLS) mode, which is the default for this example unless you set a -Dssl VM param. As we do not set the HOST header some servers do reject the upgrade request.
Modifications:
Set the HOST header
Result:
Fixes https://github.com/netty/netty/issues/9115.
Motivation:
As brought up in https://github.com/netty/netty/issues/8998, JKS can be substantially faster than pkcs12, JDK's new default. Without an option to set the KeyStore type you must change the configuration of the entire JVM which is impractical.
Modification:
- Allow to specify KeyStore type
- Add test case
Result:
Fixes https://github.com/netty/netty/issues/8998.
Motivation:
HttpHelloWorldServer example works incorrect for HTTP 1.1, the value of header connection is always set to close for each request.
Modification:
Correctly set header
Result:
Fixed HttpHelloWorldServerHandler for handling HTTP 1.0/1.1
Motivation:
"Connection: close" header should be specified each time we're going
to close an underlying TCP connection when sending HTTP/1.1 reply.
Modifications:
Introduces changes made in #8914 for the following examples:
* WebSocket index page and WebSocket server handler
* HelloWorld server
* SPDY server handler
* HTTP/1.1 server handler from HTTP/2 HelloWorld example
* HTTP/1.1 server handler from tiles example
Result:
Keep-Alive connections management conforms with RFCs.
Motivation:
We can just use a local variable in HttpUploadServerHandler and so make the example code a bit cleaner.
Modifications:
Use local variable.
Result:
Fixes https://github.com/netty/netty/issues/8892.
Motivation:
Simple rules:
* close the connection when sending any error
* specify "Connection: close" header when closing the connection
* successful responses should keep the connection intact when otherwise is not requested by the client
Modifications:
* "send response and cleanup the connection" logic moved to a helper
* for all successful responses set "Content-Lenght" header
* do not specify "Connection: Keep-Alive" header as far it's a default for HTTP/1.1
* set "Connection: close" header when necessary
Result:
Keep-Alive connections management is inlined with RFCs.
Motivation:
Netty is very widely used which can lead to a lot of pain when we break API / ABI. We should make use japicmp-maven-plugin during the build to verify we do not introduce breakage by mistake.
Modifications:
- Add japicmp-maven-plugin to the build process
- Fix a method signature change in HttpProxyHandler that was flagged as a possible problem.
Result:
Ensure no API/ABI breakage accour between releases.
Motivation:
In most cases, HttpMethod instance is built from the factory method and the same instance is taken for known Http Methods. So we can implement fast path for equals().
Modification:
Replace == checks with HttpMethod.equals;
Use this == o within HttpMethod.equals;
Replaced known new HttpMethod with HttpMethod.valueOf;
Result:
Comparisons should be a bit faster in some cases.
Motivation:
We need to update to a new checkstyle plugin to allow the usage of lambdas.
Modifications:
- Update to new plugin version.
- Fix checkstyle problems.
Result:
Be able to use checkstyle plugin which supports new Java syntax.
Motivation:
Most of the maven modules do not explicitly declare their
dependencies and rely on transitivity, which is not always correct.
Modifications:
For all maven modules, add all of their dependencies to pom.xml
Result:
All of the (essentially non-transitive) depepdencies of the modules are explicitly declared in pom.xml
Motivation:
We currently depend on slf4j in an transitive way in one of our classes in the examples. We should not do this.
Modifications:
Remove logging in example.
Result:
Remove not needed dependency.
Motivation:
After #7527 fix there is no need to manually release chunks (HttpData) during file upload as they will be released on HttpPostRequestDecoder.destroy().
Modification:
HttpUploadServer example doesn't release chunks manually (doesn't call data.release()).
Result:
Fixes#7695 and #7689
Motivation:
MemcacheClientHandler.channelRead(...) need to release the frame after it prints out its content to not introduce a memory leak.
Modifications:
Call release() on the frame.
Result:
Example has no leak any more.
Motivation:
We need to release the inbound data to ensure there are no leaks.
Modifications:
Extend SimpleChannelInboundHandler which will release inbound data by default.
Result:
No more leaks.
Motivation:
Java 11 will be out soon, so we should be able to build (and run tests) netty.
Modifications:
- Add dependency that is needed till Java 11
- Adjust tests so these also pass on Java 11 (SocketChannelImpl.close() behavious a bit differently now).
Result:
Build also works (and tests pass) on Java 11.
Motivation:
At the moment we use a ByteBuf as the payload for a http2 frame. This complicates life-time management a lot with no real gain and also may produce more objects then needed. We should just use a long as it is required to be 8 bytes anyway.
Modifications:
Use long for ping payloads.
Result:
Fixes [#7629].
Motivation:
Even if it's a super micro-optimization (most JVM could optimize such
cases in runtime), in theory (and according to some perf tests) it
may help a bit. It also makes a code more clear and allows you to
access such methods in the test scope directly, without instance of
the class.
Modifications:
Add 'static' modifier for all methods, where it possible. Mostly in
test scope.
Result:
Cleaner code with proper 'static' modifiers.
Motivation:
The `AsciiString#toString` method calculate string value and cache it into field. If an `AsciiString` created from the `String` value, we can avoid rebuilding strings if we cache them immediately when creating `AsciiString`. It would be useful for constants strings, which already stored in the JVMs string table, or in cases where an unavoidable `#toString `method call is assumed.
Modifications:
- Add new static method `AsciiString#cache(String)` which save string value into cache field.
- Apply a "benign" data race in the `#hashCode` and `#toString` methods.
Result:
Less memory usage in some `AsciiString` use cases.
Motivation:
Our http2 child channel implementation was not 100 % complete and had a few bugs. Beside this the performance overhead was non-trivial.
Modifications:
There are a lot of modifications, the most important....
* Http2FrameCodec extends Http2ConnectionHandler and Http2MultiplexCodec extends Http2FrameCodec to reduce performance heads and inter-dependencies on handlers in the pipeline
* Correctly handle outbound flow control for child channels
* Support unknow frame types in Http2FrameCodec and Http2MultiplexCodec
* Use a consistent way how to create Http2ConnectionHandler, Http2FrameCodec and Http2MultiplexCodec (via a builder)
* Remove Http2Codec and Http2CodecBuilder as the user should just use Http2MultipleCodec and Http2MultiplexCodecBuilder now
* Smart handling of flushes from child channels to reduce overhead
* Reduce object allocations
* child channels always use the same EventLoop as the parent Channel to reduce overhead and simplify implementation.
* Not extend AbstractChannel for the child channel implementation to reduce overhead in terms of performance and memory usage
* Remove Http2FrameStream.managedState(...) as the user of the child channel api should just use Channel.attr(...)
Result:
Http2MultiplexCodec (and so child channels) and Http2FrameCodec are more correct, faster and more feature complete.
