标签：#netty

With protocol values and message framing complete, Stage 2 delivered the first end-to-end call: plaintext h2c unary RPC. This is already on main , and Stage 3 and Stage 4 subsequently completed all four RPC cardinalities on the same transport primitive. Previous: Building a Leak-Safe gRPC Frame Decoder on Reactor Netty Method Descriptor Is Where Protocol Meets Types A method requires a precise service name, method name, cardinality, and request/response marshallers: var echo = new GrpcMethod <>( "testing.EchoService" , "Echo" , GrpcMethod . Cardinality . UNARY , new ProtobufMarshaller <>( StringValue . parser ()), new ProtobufMarshaller <>( StringValue . parser ())); The generated path must be: /testing.EchoService/Echo The service registry matches by exact full path. An unknown path returns UNIMPLEMENTED ; registering the same path twice fails immediately when building the service definition. Server Validates Protocol Before Subscribing to Business Logic ReactorGrpcServer uses Reactor Netty h2c: DisposableServer bound = HttpServer . create () . host ( host ) . port ( port ) . protocol ( HttpProtocol . H2C ) . handle ( handler: : handle ) . bindNow ( Duration . ofSeconds ( 10 )); Incoming requests are validated in order: HTTP method must be POST; content-type must be application/grpc or application/grpc+... ; te must declare trailers; path must exist; currently only unary cardinality is allowed; metadata and message size must not exceed limits. Only after validation passes does it create a GrpcCallContext and subscribe to the request body, preventing invalid requests from entering the business handler. HTTP 200 Does Not Mean RPC Success The server writes a compatible content-type first; the final status comes from trailing headers: response . status ( 200 ) . header ( HttpHeaderNames . CONTENT_TYPE , "application/grpc+proto" ); response . trailerHeaders ( trailers -> { GrpcException error = terminal . get (); if ( error == null ) { writeStatus ( trailers , GrpcStatu

This is the second article in my grpc-reactor series. The first article explains why I chose to build the runtime directly on Reactor Netty and where its compatibility boundary sits. This article moves one layer down into the Stage 1 protocol implementation: the frame decoder that every RPC shape relies on. gRPC protobuf messages are not written directly as raw bytes into HTTP/2 DATA frames. Every message starts with a five-byte envelope: byte 0 bit 0 indicates compression; bits 1-7 must be zero bytes 1-4 unsigned big-endian payload length byte 5..n protobuf message, or its compressed representation Encoding this envelope is straightforward. The difficult part is decoding it without assuming that one input buffer contains one complete frame. HTTP/2, TCP, and Reactor Netty do not promise that buffer boundaries will line up with gRPC message boundaries. This post describes the Stage 1 protocol layer. The project has since progressed beyond it, but the ownership and bounded-decoding rules introduced here remain the foundation for the later transport stages. Encoding Must Define Ownership The contract of GrpcFrameCodec.encode is deliberately explicit: the returned frame and the input message have independent lifetimes. Encoding must not move the input reader index or release the input buffer. The implementation currently copies the readable bytes into a byte array before applying compression: public static ByteBuf encode ( ByteBufAllocator allocator , ByteBuf message , GrpcCompression . Codec compression ) { boolean compressed = ! compression . name (). equals ( "identity" ); byte [] payload = new byte [ message . readableBytes ()]; message . getBytes ( message . readerIndex (), payload ); if ( compressed ) { payload = compression . compress ( payload ); } return allocator . buffer ( GrpcFrameCodec . HEADER_SIZE + payload . length ) . writeByte ( compressed ? 1 : 0 ) . writeInt ( payload . length ) . writeBytes ( payload ); } This is not a zero-copy implementation, and