Add root cause exception when throwing PrematureCloseException

[pderop]

Reactor Netty’s HttpClient relies on Netty’s Http2FrameCodecBuilder. This codec, by default, enforces the MAX_HEADER_LIST_SIZE found in the SETTINGS sent by the server, meaning that If a request’s header list size exceeds the SETTINGS MAX_HEADER_LIST_SIZE limit, then HpackEncoder throws a HeaderListSizeException. Consequently, the request is not sent, and the client receives a PrematureCloseException error without any details.

Let's just add more specific root cause to the PrematureCloseException in order to make it meaningful in the case the request header size exceeds MAX_HEADER_LIST_SIZE (or if whatever Netty Http2 Codec exceptions are caught while writing the request out).

Example:

reactor.netty.http.client.PrematureCloseException: Connection prematurely closed BEFORE response
Caused by: io.netty.handler.codec.http2.Http2Exception$HeaderListSizeException: Header size exceeded max allowed size (1024)

Fixes #2927

[pderop]

@violetagg , can you take a look ? I don't think the failures from macos-native and windows-2029 are related.

PS: I have set the label to enhancement because this is not a BUG fix per se, but I however have targeted the PR to 1.0.x because I think this simple improvement is worth it.

thanks.

[violetagg]

Thanks

[pderop]

@violetagg , thanks for your review.

[pderop]

The Merge done in the netty5 branch is not working, and needs to be completed with another PR, and for the moment, the testIssue2927_H2C and testIssue2927 tests are disabled in netty5 branch.

The problem in netty5 is that when the HeaderListSizeException is thrown, then:

1. first, the HttpClientOperations.onInboundClose() is invoked -> here, no unprocessedOutboundError, so the PrematureCloseException is logged without the root cause exception.
2. and right after, the ChannelOperations.onError(Throwable t) method is called .. but this too late, because the HttpClientOperations.onInboundClose() method has already logged the PrematureCloseExeption without the HeaderListSizeException root cause exception.