Support server-streaming in transcoding - #284
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This PR depends on #281 |
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| === Server-streaming responses | ||
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| Server-streaming RPCs (`rpc Foo (Req) returns (stream Resp)`) are transcoded by emitting the response over chunked transfer encoding. The wire format is selected per-request from the HTTP `Accept` header so clients can pick the encoding that fits their consumption pattern without any server configuration: |
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"according to the HTTP accept header letting the client choose the most appropriate encoding"
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| # data: {"payload":"second"} | ||
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| If the RPC terminates with a non-OK gRPC status before any message has been written, the response is finished with the corresponding HTTP status code and no body. If messages have already been written, the stream ends (with the closing `]` for JSON array mode). Mid-stream errors cannot be signalled on the body since the HTTP status was already sent. |
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Rather:
- gRPC trailers-only response sends the corresponding HTTP status error without content
- gRPC trailers response terminates the response with
], such error cannot be reported to the client
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| If the RPC terminates with a non-OK gRPC status before any message has been written, the response is finished with the corresponding HTTP status code and no body. If messages have already been written, the stream ends (with the closing `]` for JSON array mode). Mid-stream errors cannot be signalled on the body since the HTTP status was already sent. | ||
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| Client-streaming and bidirectional-streaming RPCs are not supported by transcoding. |
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rather : Transcoding does not support ...
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A few docs style wording changes would improve the quality.
… formatting. Motivation: - Extend JSON transcoding support for server-streaming RPCs to enhance compatibility with streaming APIs. - Improve response flexibility with support for JSON Array, NDJSON, and SSE formats based on the `Accept` header. Changes: - Added `streaming` and `StreamFormat` fields to `TranscodingGrpcOutboundStream` for response format negotiation. - Implemented JSON Array, NDJSON, and SSE response formatting for server-streaming. - Derived the streaming cardinality from `ServiceMethod#serverStreaming()`. - Updated `MessageWeaver` to handle `JsonObject` outputs for request/response weaving. - Modified tests to validate new streaming response formats and HTTP transcoding logic. Signed-off-by: Daniel Fiala <danfiala23@gmail.com>
Motivation: - The server-streaming transcoding formats were only covered by unit tests using hand-built service methods, leaving the protoc plugin path untested end to end. Changes: - Exercise the generated `StreamingTranscodingGreeter` service method over HTTP for the JSON array, NDJSON and SSE formats. - Cover the empty stream and the coexistence of the transcoded and gRPC routes for the same method. Signed-off-by: Daniel Fiala <danfiala23@gmail.com>
Motivation: - `GrpcServer#addService` only registered the canonical `/package.Service/Method` path, so the HTTP rules of a transcoded service method were ignored and the transcoded routes returned a 500. `GrpcServer#callHandler` already mounts these paths. Changes: - Mount the `MountPoint` paths of a service method in `addService`, like `callHandler` does. - Add integration tests binding a transcoded unary and server-streaming service with `addService`. Signed-off-by: Daniel Fiala <danfiala23@gmail.com>
… message. Motivation: Transcoding defers the HTTP head until the response body is known, so writeHead returns a promise resolved by writeUnaryMessage. A unary call that ends without ever writing a message never resolves it and leaves the caller waiting. Changes: Resolve the head promise from writeEnd when it is still pending. Fix the indentation of the SSE branch.
Motivation: - Review feedback on the server-streaming transcoding section asked for a more concise wording of the content negotiation and error reporting paragraphs. Changes: - Describe the wire format as selected according to the HTTP `accept` header. - Split the error reporting paragraph into the trailers-only and trailers cases. - Reword the unsupported streaming modes sentence. Signed-off-by: Daniel Fiala <danfiala23@gmail.com>
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Motivation:
Acceptheader.Changes:
streamingandStreamFormatfields toTranscodingGrpcOutboundStreamfor response format negotiation.MessageWeaverto handleJsonObjectoutputs for request/response weaving.grpc-service.mustache) and tests to support method-levelisManyOutputconfigurations.