Motivation:
We not correctly managed the life-cycle of the buffer / frames in our http2 multiplex example which lead to a memory leak.
Modifications:
- Correctly release frame if not echo'ed back the remote peer.
- Not retain content before echo back to remote peer.
Result:
No more leak in the example, fixes [#6636].
https://github.com/netty/netty-tcnative/pull/215
Motivation
OCSP stapling (formally known as TLS Certificate Status Request extension) is alternative approach for checking the revocation status of X.509 Certificates. Servers can preemptively fetch the OCSP response from the CA's responder, cache it for some period of time, and pass it along during (a.k.a. staple) the TLS handshake. The client no longer has to reach out on its own to the CA to check the validity of a cetitficate. Some of the key benefits are:
1) Speed. The client doesn't have to crosscheck the certificate.
2) Efficiency. The Internet is no longer DDoS'ing the CA's OCSP responder servers.
3) Safety. Less operational dependence on the CA. Certificate owners can sustain short CA outages.
4) Privacy. The CA can lo longer track the users of a certificate.
https://en.wikipedia.org/wiki/OCSP_staplinghttps://letsencrypt.org/2016/10/24/squarespace-ocsp-impl.html
Modifications
https://www.openssl.org/docs/man1.0.2/ssl/SSL_set_tlsext_status_type.html
Result
High-level API to enable OCSP stapling
Motivation:
HTTP/2 support two ways to start on a no-tls tcp connection,
http/1.1 upgrade and prior knowlege methodology to start HTTP/2.
Currently, the http2-server from example only support
starting by upgrade. I think we can do a simple dispatch by peek first
bytes from inbound that match to prior knowledge preface or not and
determine which handlers to set into pipeline.
Modifications:
Add ClearTextHttp2ServerUpgradeHandler to support start HTTP/2 via clear
text with two approach. And update example/http2-server to support
this functionality.
Result:
netty HTTP/2 and the example http2-server accept for two ways to start
HTTP/2 over clear text.
Fixed memory leak problem
Update fields to final
Rename ClearText to cleartext
Addressed comments for code improvement
- Always prefer static, final, and private if possible
- Add UnstableApi annotation
- Used EmbeddedChannel.readInbound instead of unhandled inbound handler
- More assertion
Update javadoc for CleartextHttp2ServerUpgradeHandler
Rename ClearTextHttp2ServerUpgradeHandler to CleartextHttp2ServerUpgradeHandler
Removed redundant code about configure pipeline
nit: PriorKnowledgeHandler
Removed Mockito.spy, investigate conn state instead
Add Http2UpgradeEvent
Check null of the constructor arguments
Rename Http2UpgradeEvent to PriorKnowledgeUpgradeEvent
Update unit test
Motivation:
Calling a static method is faster then dynamic
Modifications:
Add 'static' keyword for methods where it missed
Result:
A bit faster method calls
Motivation:
2fd42cfc6b fixed a bug related to encoding headers but it also introduced a throws statement onto the Http2FrameWriter methods which write headers. This throws statement makes the API more verbose and is not necessary because we can communicate the failure in the ChannelFuture that is returned by these methods.
Modifications:
- Remove throws from all Http2FrameWriter methods.
Result:
Http2FrameWriter APIs do not propagate checked exceptions.
Motivation:
Currently Netty does not wrap socket connect, bind, or accept
operations in doPrivileged blocks. Nor does it wrap cases where a dns
lookup might happen.
This prevents an application utilizing the SecurityManager from
isolating SocketPermissions to Netty.
Modifications:
I have introduced a class (SocketUtils) that wraps operations
requiring SocketPermissions in doPrivileged blocks.
Result:
A user of Netty can grant SocketPermissions explicitly to the Netty
jar, without granting it to the rest of their application.
Motivation:
If the HPACK Decoder detects that SETTINGS_MAX_HEADER_LIST_SIZE has been violated it aborts immediately and sends a RST_STREAM frame for what ever stream caused the issue. Because HPACK is stateful this means that the HPACK state may become out of sync between peers, and the issue won't be detected until the next headers frame. We should make a best effort to keep processing to keep the HPACK state in sync with our peer, or completely close the connection.
If the HPACK Encoder is configured to verify SETTINGS_MAX_HEADER_LIST_SIZE it checks the limit and encodes at the same time. This may result in modifying the HPACK local state but not sending the headers to the peer if SETTINGS_MAX_HEADER_LIST_SIZE is violated. This will also lead to an inconsistency in HPACK state that will be flagged at some later time.
Modifications:
- HPACK Decoder now has 2 levels of limits related to SETTINGS_MAX_HEADER_LIST_SIZE. The first will attempt to keep processing data and send a RST_STREAM after all data is processed. The second will send a GO_AWAY and close the entire connection.
- When the HPACK Encoder enforces SETTINGS_MAX_HEADER_LIST_SIZE it should not modify the HPACK state until the size has been checked.
- https://tools.ietf.org/html/rfc7540#section-6.5.2 states that the initial value of SETTINGS_MAX_HEADER_LIST_SIZE is "unlimited". We currently use 8k as a limit. We should honor the specifications default value so we don't unintentionally close a connection before the remote peer is aware of the local settings.
- Remove unnecessary object allocation in DefaultHttp2HeadersDecoder and DefaultHttp2HeadersEncoder.
Result:
Fixes https://github.com/netty/netty/issues/6209.
Motivation:
The HTTP/2 helloworld client example has 2 bugs:
1. HttpResponseHandler has a map which is accessed from multiple threads, but the map is not thread safe.
2. Requests are flushed and maybe completely written and the responses may be received/processed by Netty before an element is inserted into the HttpResponseHandler map. This may result in an 'unexpected message' error even though the message has actually been sent.
Modifications:
- HttpResponseHandler should use a thread safe map
- Http2Client shouldn't flush until entries are added to the HttpResponseHandler map
Result:
Fixes https://github.com/netty/netty/issues/6165.
Motivation:
The responsibility for retaining the settings values and enforcing the settings constraints is spread out in different areas of the code and may be initialized with different values than the default specified in the RFC. This should not be allowed by default and interfaces which are responsible for maintaining/enforcing settings state should clearly indicate the restrictions that they should only be set by the codec upon receipt of a SETTINGS ACK frame.
Modifications:
- Encoder, Decoder, and the Headers Encoder/Decoder no longer expose public constructors that allow the default settings to be changed.
- Http2HeadersDecoder#maxHeaderSize() exists to provide some bound when headers/continuation frames are being aggregated. However this is roughly the same as SETTINGS_MAX_HEADER_LIST_SIZE (besides the 32 byte octet for each header field) and can be used instead of attempting to keep the two independent values in sync.
- Encoding headers now enforces SETTINGS_MAX_HEADER_LIST_SIZE at the octect level. Previously the header encoder compared the number of header key/value pairs against SETTINGS_MAX_HEADER_LIST_SIZE instead of the number of octets (plus 32 bytes overhead).
- DefaultHttp2ConnectionDecoder#onData calls shouldIgnoreHeadersOrDataFrame but may swallow exceptions from this method. This means a STREAM_RST frame may not be sent when it should for an unknown stream and thus violate the RFC. The exception is no longer swallowed.
Result:
Default settings state is enforced and interfaces related to settings state are clarified.
Motivation:
We need to duplicate the buffer before passing it to writeBytes(...) as it will increase the readerIndex().
Modifications:
Call duplicate().
Result:
No more IndexOutOfBoundsException when runing the multiplex example.
Motivation:
We called ctx.flush() which is not correct as it will not call flowController().writePendingBytes().
Modifications:
Call flush(ChannelHandlerContext) and so also call flowController().writePendingBytes().
Result:
Correct http2 example
Motivation:
Http2ServerInitializer uses a SimpleChannelHandler in an attempt to ease putting an HttpObjectAggregator in the pipeline when no upgrade is attempted. However the message is double released because it is fired up the pipeline (which will be released) and also released by SimpleChannelHandler in a finally block.
Modifications:
- Retain the message if we fire it up the pipeline
Result:
HTTP/2 examples don't encounter a reference count error if no upgrade was attempted.
Motivation:
As we use compression in the websocketx example we need to allow extensions as ohterwise the example not works.
Modifications:
Allow extensions.
Result:
websocketx example does work.
Motivation:
The HTTP Static File Server seems to ignore filenames that doesn't contains only latin characters, but these days people wish to serve files in other languages, or even include some emojis in the filename. Although these files are not displayed on the directory listing, they are accessible by HTTP requests. This fix will make such files more visible.
Modifications:
I've changed the ALLOWED_FILE_NAME pattern to disallow only files that starts with underline, minus or a dot (such as .htaccess), and hide other "unsafe" filenames that may be used to trigger some security issues. Other filenames, including the space character are allowed.
I've also added charset encoding to the directory listing, because the browser default MAY be configured for ISO-8859-1 instead of UTF-8.
Result:
Directory listing will work for files that contains the space character, as well as other Unicode characters.
Motivation:
When Netty HTTP Static File Server does directory listing, it does expose the user.dir environment variable to the user. Although it doesn't a security issue, it is a bad practice to show it, and the user does expect to see the server virtual root instead, which is the absolute path as mentioned in the RFC.
Modifications:
the sendListing method receives a third argument, which is the requested URI, and this is what should be displayed on the page instead of the filesystem path.
Result:
The directory listing pages will show the virtual path as described in the URI and not the real filesystem path.
Removed fallback method
Motivation:
Socks5 proxy supports resolve domain at the server side. When testing
with curl, the SocksServer in example package only works for proxy
request with IP, not with domain name (`--socks5` vs
`--socks5-hostname`). As curl is widely used, it should work with
the example provided.
Modifications:
Passing address and port to the Socks5CommandResponse, so that it
works for curl.
Result:
`curl --socks5-hostname` works as expected.
Motivation:
We not need to mark the field as volatile and so this may confuse people.
Modifications:
Remove volatile and add comment to explain why its not needed.
Result:
More correct example.
Motivation:
Quote from issue 4914:
"Http2MultiplexCodec currently does two things: mapping the existing h2 API to frames and managing the child channels.
It would be better if the two parts were separated. This would allow less-coupled development of the HTTP/2 handlers (flow control could be its own handler, for instance) and allow applications to insert themselves between all streams and the codec, which permits custom logic and could be used, in part, to implement custom frame types.
It would also greatly ease testing, as the child channel could be tested by itself without dealing with how frames are encoded on the wire."
Modifications:
- Split the Http2MultiplexCodec into Http2FrameCodec and Http2MultiplexCodec. The Http2FrameCodec interacts with the existing HTTP/2 callback-based API, while the Http2MulitplexCodec is completely independent of it and simply multiplexes Http2StreamFrames to the child channels. Additionally, the Http2Codec handler is introduced, which is a convenience class that simply sets up the Http2FrameCodec and Http2MultiplexCodec in the channel pipeline and removes itself.
- Improved test coverage quite a bit.
Result:
- The original Http2MultiplexCodec is split into Http2FrameCodec and Http2MultiplexCodec.
- More tests for higher confidence in the code.
Related: #4333#4421#5128
Motivation:
slice(), duplicate() and readSlice() currently create a non-recyclable
derived buffer instance. Under heavy load, an application that creates a
lot of derived buffers can put the garbage collector under pressure.
Modifications:
- Add the following methods which creates a non-recyclable derived buffer
- retainedSlice()
- retainedDuplicate()
- readRetainedSlice()
- Add the new recyclable derived buffer implementations, which has its
own reference count value
- Add ByteBufHolder.retainedDuplicate()
- Add ByteBufHolder.replace(ByteBuf) so that..
- a user can replace the content of the holder in a consistent way
- copy/duplicate/retainedDuplicate() can delegate the holder
construction to replace(ByteBuf)
- Use retainedDuplicate() and retainedSlice() wherever possible
- Miscellaneous:
- Rename DuplicateByteBufTest to DuplicatedByteBufTest (missing 'D')
- Make ReplayingDecoderByteBuf.reject() return an exception instead of
throwing it so that its callers don't need to add dummy return
statement
Result:
Derived buffers are now recycled when created via retainedSlice() and
retainedDuplicate() and derived from a pooled buffer
Motivation:
Currently the way a 'null' origin, a request that most often indicated
that the request is coming from a file on the local file system, is
handled is incorrect. We are currently returning a wildcard origin '*'
but should be returning 'null' for the 'Access-Control-Allow-Origin'
which is valid according to the specification [1].
Modifications:
Updated CorsHandler to add a 'null' origin instead of the '*' origin in
the case the request origin is 'null.
Result:
All test pass and the CORS example as does the cors.html example if you
try to serve it by opening the file directly in a web browser.
[1]
https://www.w3.org/TR/cors/#access-control-allow-origin-response-header
Motivation:
- Add an example Redis client using codec-redis.
Modifications:
- Add an example Redis client that reads input from STDIN and writes output to STDOUT.
Result:
- Added an example Redis client using codec-redis.
Motivation:
We lately added ByteBuf.isReadOnly() which allows to detect if a buffer is read-only or not. We should add ByteBuf.asReadOnly() to allow easily access a read-only version of a buffer.
Modifications:
- Add ByteBuf.asReadOnly()
- Deprecate Unpooled.unmodifiableBuffer(Bytebuf)
Result:
More consistent api.
Motivation:
People need to set all length fields manually when creating a memcache message and it's error prone. See #2736 for more dicussion.
Modifications:
This patch adds the logic to update the keyLength, extrasLength and totalBodyLength when key, extras or content is set.
Result:
The length fields of memcache messages will be updated automatically.
Motivation:
This allows using handlers for Streams in normal Netty-style. Frames are
read/written to the channel as messages, not directly as a
callback/method call. Handlers allow mixing and can ease HTTP/1 and
HTTP/2 interoperability by eventually supporting HTTP/1 handlers in
HTTP/2 and vise versa.
Modifications:
New handler Http2MultiplexCodec that converts from the current HTTP/2
API to a message-based API and child channels for streams.
Result:
The basics are done for server-side: new streams trigger creation of new
channels in much the same appearance to how new connections trigger new
channel creation. The basic frames HEADERS and DATA are handled, but
also GOAWAY and RST_STREAM.
Inbound flow control is implemented, but outbound is not. That will be
done later, along with not completing write promises on the child
channel until the write actually completes on the parent.
There is not yet support for outbound priority/weight, push promises,
and many other features.
There is a generic Object that may be set on stream frames. This also
paves the way for client-side support which needs a way to refer to
yet-to-be-created streams (due to how HEADERS allocates a stream id, and
the allocation order must be the same as transmission order).
Motivation:
It will be easier to support websockets in server application by using WebSocketServerProtocolHandshakeHandler class and not reinvent its functionality. But currently it handles all http requests as if they were websocket handshake requests.
Modifications:
Check if http request path is equals to adjusted websocket path.
Fixed example of websocket server implementation.
Result:
WebSocketServerProtocolHandshakeHandler handles only websocket handshake requests.
Motivation:
The key can be ByteBuf to avoid converting between ByteBuf and String. See #3689.
Modifications:
Replace the type of key with ByteBuf.
Result:
The type of key becomes ByteBuf.
Motivation:
WebSocketClientCompressionHandler is stateless so it should be @Sharable.
Modifications:
Add @Sharable annotation to WebSocketClientCompressionHandler, make constructor private and add static field to get the instance.
Result:
Less object creation.
Motivation:
Boxing/unboxing can be avoided.
Modifications:
Use parseInt/parseLong to avoid unnecessary boxing/unboxing.
Result:
Remove unnecessary boxing/unboxing.
Motivation:
Warnings in IDE, unclean code, negligible performance impact.
Modification:
Deletion of unused imports
Result:
No more warnings in IDE, cleaner code, negligible performance improvement.
Motivation:
Javadoc reports errors about invalid docs.
Modifications:
Fix some errors reported by javadoc.
Result:
A lot of javadoc errors are fixed by this patch.
Motivation:
We have websocket extension support (with compression) in old master. We should port this to 4.1
Modifications:
Backport relevant code.
Result:
websocket extension support (with compression) is now in 4.1.
Related: #4572#4574
Motivation:
Consistency in our builder API design
Modifications:
- Add AbstractInboundHttp2ToHttpAdapterBuilder
- Replace the old 'Builder's with InboundHttp2ToHttpAdapterBuilder and
InboundHttp2ToHttpPriorityAdapterBuilder
Result:
Builder API consistency
Motivation:
Consistency in API design
Modifications:
- Deprecate CorsConfig.Builder and its factory methods
- Deprecate CorsConfig.DateValueGenerator
- Add CorsConfigBuilder and its factory methods
- Fix typo (curcuit -> circuit)
Result:
Consistency with other builder APIs such as SslContextBuilder and
Http2ConnectionHandlerBuilder
Related: #4572
Motivation:
- A user might want to extend Http2ConnectionHandler and define his/her
own static inner Builder class that extends
Http2ConnectionHandler.BuilderBase. This introduces potential
confusion because there's already Http2ConnectionHandler.Builder. Your
IDE will warn about this name duplication as well.
- BuilderBase exposes all setters with public modifier. A user's Builder
might not want to expose them to enforce it to certain configuration.
There's no way to hide them because it's public already and they are
final.
- BuilderBase.build(Http2ConnectionDecoder, Http2ConnectionEncoder)
ignores most properties exposed by BuilderBase, such as
validateHeaders, frameLogger and encoderEnforceMaxConcurrentStreams.
If any build() method ignores the properties exposed by the builder,
there's something wrong.
- A user's Builder that extends BuilderBase might want to require more
parameters in build(). There's no way to do that cleanly because
build() is public and final already.
Modifications:
- Make BuilderBase and Builder top-level so that there's no duplicate
name issue anymore.
- Add AbstractHttp2ConnectionHandlerBuilder
- Add Http2ConnectionHandlerBuilder
- Add HttpToHttp2ConnectionHandlerBuilder
- Make all builder methods in AbstractHttp2ConnectionHandlerBuilder
protected so that a subclass can choose which methods to expose
- Provide only a single build() method
- Add connection() and codec() so that a user can still specify
Http2Connection or Http2Connection(En|De)coder explicitly
- Implement proper state validation mechanism so that it is prevented
to invoke conflicting setters
Result:
Less confusing yet flexible builder API
Motivation:
The HTTP/2 client example is not validating the results of ALPN if TLS is enabled.
Modifications:
- Use ApplicationProtocolNegotiationHandler to validate ALPN results.
Result:
Client example validates ALPN results.
Motivation:
The proxy example contains some code that is not needed. This can confuse the reader.
Modifications:
Remove the not needed ctx.write(...).
Result:
Less confusing code.
Motivation:
Using the builder pattern for Http2ConnectionHandler (and subclasses) would be advantageous for the following reasons:
1. Provides the consistent construction afforded by the builder pattern for 'optional' arguments. Users can specify these options 1 time in the builder and then re-use the builder after this.
2. Enforces that the Http2ConnectionHandler's internals (decoder Http2FrameListener) are initialized after construction.
Modifications:
- Add an extensible builder which can be used to build Http2ConnectionHandler objects
- Update classes which inherit from Http2ConnectionHandler
Result:
It is easier to specify options and construct Http2ConnectionHandler objects.
Motivation:
It is often the case that implementations of Http2FrameListener will want to send responses when data is read. The Http2FrameListener needs access to the Http2ConnectionHandler (or the encoder contained within) to be able to send responses. However the Http2ConnectionHandler requires a Http2FrameListener instance to be passed in during construction time. This creates a cyclic dependency which can make it difficult to cleanly accomplish this relationship.
Modifications:
- Add Http2ConnectionDecoder.frameListener(..) method to set the frame listener. This will allow the listener to be set after construction.
Result:
Classes which inherit from Http2ConnectionHandler can more cleanly set the Http2FrameListener.
Motivation:
Http2CodecUtils has some static variables which are defined as Strings instead of CharSequence. One of these defines is used as a header name and should be AsciiString.
Modifications:
- Change the String defines in Http2CodecUtils to CharSequence
Result:
Types are more consistently using CharSequence and adding the upgrade header will require less work.
Motivation:
The DefaultHttp2Headers code is throwing a IllegalArgumentException if an invalid character is detected. This is being ignored by the HTTP/2 codec instead of generating a GOAWAY.
Modifications:
- Throw a Http2Exception of type PROTOCOL_ERROR in accordance with https://tools.ietf.org/html/rfc7540#section-8.1.2.6
- Update examples which were building invalid headers
Result:
More compliant with https://tools.ietf.org/html/rfc7540#section-8.1.2.6
Motivation:
There currently exists http.HttpUtil, http2.HttpUtil, and http.HttpHeaderUtil. Having 2 HttpUtil methods can be confusing and the utilty methods in the http package could be consolidated.
Modifications:
- Rename http2.HttpUtil to http2.HttpConversionUtil
- Move http.HttpHeaderUtil methods into http.HttpUtil
Result:
Consolidated utilities whose names don't overlap.
Fixes https://github.com/netty/netty/issues/4120
Motivation:
A degradation in performance has been observed from the 4.0 branch as documented in https://github.com/netty/netty/issues/3962.
Modifications:
- Simplify Headers class hierarchy.
- Restore the DefaultHeaders to be based upon DefaultHttpHeaders from 4.0.
- Make various other modifications that are causing hot spots.
Result:
Performance is now on par with 4.0.
Motivation:
We noticed that the headers implementation in Netty for HTTP/2 uses quite a lot of memory
and that also at least the performance of randomly accessing a header is quite poor. The main
concern however was memory usage, as profiling has shown that a DefaultHttp2Headers
not only use a lot of memory it also wastes a lot due to the underlying hashmaps having
to be resized potentially several times as new headers are being inserted.
This is tracked as issue #3600.
Modifications:
We redesigned the DefaultHeaders to simply take a Map object in its constructor and
reimplemented the class using only the Map primitives. That way the implementation
is very concise and hopefully easy to understand and it allows each concrete headers
implementation to provide its own map or to even use a different headers implementation
for processing requests and writing responses i.e. incoming headers need to provide
fast random access while outgoing headers need fast insertion and fast iteration. The
new implementation can support this with hardly any code changes. It also comes
with the advantage that if the Netty project decides to add a third party collections library
as a dependency, one can simply plug in one of those very fast and memory efficient map
implementations and get faster and smaller headers for free.
For now, we are using the JDK's TreeMap for HTTP and HTTP/2 default headers.
Result:
- Significantly fewer lines of code in the implementation. While the total commit is still
roughly 400 lines less, the actual implementation is a lot less. I just added some more
tests and microbenchmarks.
- Overall performance is up. The current implementation should be significantly faster
for insertion and retrieval. However, it is slower when it comes to iteration. There is simply
no way a TreeMap can have the same iteration performance as a linked list (as used in the
current headers implementation). That's totally fine though, because when looking at the
benchmark results @ejona86 pointed out that the performance of the headers is completely
dominated by insertion, that is insertion is so significantly faster in the new implementation
that it does make up for several times the iteration speed. You can't iterate what you haven't
inserted. I am demonstrating that in this spreadsheet [1]. (Actually, iteration performance is
only down for HTTP, it's significantly improved for HTTP/2).
- Memory is down. The implementation with TreeMap uses on avg ~30% less memory. It also does not
produce any garbage while being resized. In load tests for GRPC we have seen a memory reduction
of up to 1.2KB per RPC. I summarized the memory improvements in this spreadsheet [1]. The data
was generated by [2] using JOL.
- While it was my original intend to only improve the memory usage for HTTP/2, it should be similarly
improved for HTTP, SPDY and STOMP as they all share a common implementation.
[1] https://docs.google.com/spreadsheets/d/1ck3RQklyzEcCLlyJoqDXPCWRGVUuS-ArZf0etSXLVDQ/edit#gid=0
[2] https://gist.github.com/buchgr/4458a8bdb51dd58c82b4
Motivation:
The HTTP/2 hello world example server should be expecting a FullHttpRequest when falling back to HTTP/1.x mode.
Modifications:
- HelloWorldHttp1Handler should process FullHttpRequestObjects
- Http2ServerInitializer should insert an HttpObjectAggregator into the pipeline if no upgrade was attempted
Result:
Responses from the HelloWorldHttp1Handler should only come after full HTTP requests are received.
Proposal to fix issue #3636
Motivations:
Currently, while adding the next buffers to the decoder
(`decoder.offer()`), there is no way to access to the current HTTP
object being decoded since it can only be available currently once fully
decoded by `decoder.hasNext()`.
Some could want to know the progression on the overall transfer but also
per HTTP object.
While overall progression could be done using (if available) the global
Content-Length of the request and taking into account each HttpContent
size, the per HttpData object progression is unknown.
Modifications:
1) For HTTP object, `AbstractHttpData` has 2 protected properties named
`definedSize` and `size`, respectively the supposely final size and the
current (decoded until now) size.
This provides a new method `definedSize()` to get the current value for
`definedSize`. The `size` attribute is reachable by the `length()`
method.
Note however there are 2 different ways that currently managed the
`definedSize`:
a) `Attribute`: it is reset each time the value is less than actual
(when a buffer is added, the value is increased) since the final length
is not known (no Content-Length)
b) `FileUpload`: it is set at startup from the lengh provided
So these differences could lead in wrong perception;
a) `Attribute`: definedSize = size always
b) `FileUpload`: definedSize >= size always
Therefore the comment tries to explain clearly the different behaviors.
2) In the InterfaceHttpPostRequestDecoder (and the derived classes), I
add a new method: `decoder.currentPartialHttpData()` which will return a
`InterfaceHttpData` (if any) as the current `Attribute` or `FileUpload`
(the 2 generic types), which will allow then the programmer to check
according to the real type (instance of) the 2 methods `definedSize()`
and `length()`.
This method check if currentFileUpload or currentAttribute are null and
returns the one (only one could be not null) that is not null.
Note that if this method returns null, it might mean 2 situations:
a) the last `HttpData` (whatever attribute or file upload) is already
finished and therefore accessible through `next()`
b) there is not yet any `HttpData` in decoding (body not yet parsed for
instance)
Result:
The developper has more access and therefore control on the current
upload.
The coding from developper side could looks like in the example in
HttpUloadServerHandler.
