Include SETTINGS_MAX_HEADER_LIST_SIZE in initial SETTINGS.

[buchgr]

We currently don't send SETTINGS_MAX_HEADER_LIST_SIZE as part of the initial SETTINGS frame, although we enforce it on the decoder. This is valid as of the H2 spec

For any given request, a lower limit than what is advertised MAY be enforced. The initial value of this setting is unlimited.

However, we would argue that we should still include it in the initial SETTINGS frame, cause why not? If both endpoints are gRPC Java, it would also give us better error messages, as then the local encoder would enforce the remote decode limit [1]. However, we can't currently do that cause it seems like a bug in Netty that the encoder throws a connection error and not a stream error [1], bringing down the whole connection, while only the stream should fail. I ll open a issue/PR in Netty.

[1] https://github.com/netty/netty/blob/4.1/codec-http2/src/main/java/io/netty/handler/codec/http2/internal/hpack/Encoder.java#L126

[buchgr]

Opened Netty PR netty/netty#5919

[ejona86]

Does anything need to be done here? Will the next update of Netty "just work"?

[buchgr]

@ejona86 We need to also include the max header list value in the initial settings. So add one line in client handler and one line in server handler. [1]

initialSettings.maxHeaderListSize(maxHeaderListSize);

[1] https://github.com/grpc/grpc-java/blob/master/netty/src/main/java/io/grpc/netty/NettyClientHandler.java#L156

[lukaszx0]

For posterity and people that are using versions < 1.2.x.

This fixes following stream error which gets thrown when header size is exceeded:

WARNING: Stream Error
io.netty.handler.codec.http2.Http2Exception$HeaderListSizeException: Header size exceeded max allowed size (8192)
at io.netty.handler.codec.http2.Http2Exception.headerListSizeError(Http2Exception.java:169)
at io.netty.handler.codec.http2.Http2CodecUtil.headerListSizeExceeded(Http2CodecUtil.java:252)
at io.netty.handler.codec.http2.internal.hpack.Encoder.encodeHeadersEnforceMaxHeaderListSize(Encoder.java:128)
at io.netty.handler.codec.http2.internal.hpack.Encoder.encodeHeaders(Encoder.java:112)
at io.netty.handler.codec.http2.DefaultHttp2HeadersEncoder.encodeHeaders(DefaultHttp2HeadersEncoder.java:69)
at io.netty.handler.codec.http2.DefaultHttp2FrameWriter.writeHeadersInternal(DefaultHttp2FrameWriter.java:435)
  ...