250 lines
9.0 KiB
Markdown
250 lines
9.0 KiB
Markdown
# grpc-gateway
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[](https://travis-ci.org/grpc-ecosystem/grpc-gateway)
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grpc-gateway is a plugin of [protoc](http://github.com/google/protobuf).
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It reads [gRPC](http://github.com/grpc/grpc-common) service definition,
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and generates a reverse-proxy server which translates a RESTful JSON API into gRPC.
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This server is generated according to [custom options](https://cloud.google.com/service-management/reference/rpc/google.api#http) in your gRPC definition.
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It helps you to provide your APIs in both gRPC and RESTful style at the same time.
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## Background
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gRPC is great -- it generates API clients and server stubs in many programming languages,
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it is fast, easy-to-use, bandwidth-efficient and its design is combat-proven by Google.
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However, you might still want to provide classic RESTful APIs too for some reasons --
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compatibility with languages not supported by gRPC, API backward-compatibility or aesthetics
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of RESTful architecture.
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That's what grpc-gateway helps you to do. You just need to implement your gRPC service with a small amount of custom options.
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Then the reverse-proxy generated by grpc-gateway serves RESTful API on top of the gRPC service.
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## Installation
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First you need to install ProtocolBuffers 3.0.0-beta-3 or later.
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```sh
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mkdir tmp
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cd tmp
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git clone https://github.com/google/protobuf
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cd protobuf
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./autogen.sh
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./configure
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make
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make check
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sudo make install
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```
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Then, `go get -u` as usual the following packages:
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```sh
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go get -u github.com/grpc-ecosystem/grpc-gateway/protoc-gen-grpc-gateway
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go get -u github.com/grpc-ecosystem/grpc-gateway/protoc-gen-swagger
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go get -u github.com/golang/protobuf/protoc-gen-go
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```
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## Usage
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Make sure that your `$GOPATH/bin` is in your `$PATH`.
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1. Define your service in gRPC
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your_service.proto:
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```protobuf
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syntax = "proto3";
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package example;
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message StringMessage {
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string value = 1;
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}
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service YourService {
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rpc Echo(StringMessage) returns (StringMessage) {}
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}
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```
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2. Add a [custom option](https://cloud.google.com/service-management/reference/rpc/google.api#http) to the .proto file
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your_service.proto:
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```diff
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syntax = "proto3";
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package example;
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+
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+import "google/api/annotations.proto";
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+
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message StringMessage {
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string value = 1;
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}
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service YourService {
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- rpc Echo(StringMessage) returns (StringMessage) {}
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+ rpc Echo(StringMessage) returns (StringMessage) {
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+ option (google.api.http) = {
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+ post: "/v1/example/echo"
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+ body: "*"
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+ };
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+ }
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}
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```
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3. Generate gRPC stub
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```sh
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protoc -I/usr/local/include -I. \
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-I$GOPATH/src \
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-I$GOPATH/src/github.com/grpc-ecosystem/grpc-gateway/third_party/googleapis \
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--go_out=plugins=grpc:. \
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path/to/your_service.proto
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```
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It will generate a stub file `path/to/your_service.pb.go`.
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4. Implement your service in gRPC as usual
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1. (Optional) Generate gRPC stub in the language you want.
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e.g.
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```sh
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protoc -I/usr/local/include -I. \
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-I$GOPATH/src \
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-I$GOPATH/src/github.com/grpc-ecosystem/grpc-gateway/third_party/googleapis \
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--ruby_out=. \
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path/to/your/service_proto
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protoc -I/usr/local/include -I. \
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-I$GOPATH/src \
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-I$GOPATH/src/github.com/grpc-ecosystem/grpc-gateway/third_party/googleapis \
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--plugin=protoc-gen-grpc=grpc_ruby_plugin \
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--grpc-ruby_out=. \
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path/to/your/service.proto
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```
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2. Add the googleapis-common-protos gem (or your language equivalent) as a dependency to your project.
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3. Implement your service
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5. Generate reverse-proxy
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```sh
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protoc -I/usr/local/include -I. \
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-I$GOPATH/src \
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-I$GOPATH/src/github.com/grpc-ecosystem/grpc-gateway/third_party/googleapis \
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--grpc-gateway_out=logtostderr=true:. \
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path/to/your_service.proto
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```
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It will generate a reverse proxy `path/to/your_service.pb.gw.go`.
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Note: After generating the code for each of the stubs, in order to build the code, you will want to run ```go get .``` from the directory containing the stubs.
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6. Write an entrypoint
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Now you need to write an entrypoint of the proxy server.
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```go
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package main
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import (
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"flag"
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"net/http"
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"github.com/golang/glog"
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"golang.org/x/net/context"
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"github.com/grpc-ecosystem/grpc-gateway/runtime"
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"google.golang.org/grpc"
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gw "path/to/your_service_package"
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)
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var (
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echoEndpoint = flag.String("echo_endpoint", "localhost:9090", "endpoint of YourService")
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)
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func run() error {
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ctx := context.Background()
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ctx, cancel := context.WithCancel(ctx)
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defer cancel()
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mux := runtime.NewServeMux()
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opts := []grpc.DialOption{grpc.WithInsecure()}
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err := gw.RegisterYourServiceHandlerFromEndpoint(ctx, mux, *echoEndpoint, opts)
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if err != nil {
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return err
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}
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return http.ListenAndServe(":8080", mux)
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}
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func main() {
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flag.Parse()
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defer glog.Flush()
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if err := run(); err != nil {
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glog.Fatal(err)
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}
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}
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```
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7. (Optional) Generate swagger definitions
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```sh
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protoc -I/usr/local/include -I. \
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-I$GOPATH/src \
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-I$GOPATH/src/github.com/grpc-ecosystem/grpc-gateway/third_party/googleapis \
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--swagger_out=logtostderr=true:. \
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path/to/your_service.proto
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```
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## Parameters and flags
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`protoc-gen-grpc-gateway` supports custom mapping from Protobuf `import` to Golang import path.
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They are compatible to [the parameters with same names in `protoc-gen-go`](https://github.com/golang/protobuf#parameters).
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In addition we also support the `request_context` parameter in order to use the `http.Request`'s Context (only for Go 1.7 and above).
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This parameter can be useful to pass request scoped context between the gateway and the gRPC service.
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`protoc-gen-grpc-gateway` also supports some more command line flags to control logging. You can give these flags together with parameters above. Run `protoc-gen-grpc-gateway --help` for more details about the flags.
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## More Examples
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More examples are available under `examples` directory.
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* `examplepb/echo_service.proto`, `examplepb/a_bit_of_everything.proto`: service definition
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* `examplepb/echo_service.pb.go`, `examplepb/a_bit_of_everything.pb.go`: [generated] stub of the service
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* `examplepb/echo_service.pb.gw.go`, `examplepb/a_bit_of_everything.pb.gw.go`: [generated] reverse proxy for the service
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* `server/main.go`: service implementation
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* `main.go`: entrypoint of the generated reverse proxy
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To use the same port for custom HTTP handlers (e.g. serving `swagger.json`), gRPC-gateway, and a gRPC server, see [this code example by CoreOS](https://github.com/philips/grpc-gateway-example/blob/master/cmd/serve.go) (and its accompanying [blog post](https://coreos.com/blog/gRPC-protobufs-swagger.html))
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## Features
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### Supported
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* Generating JSON API handlers
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* Method parameters in request body
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* Method parameters in request path
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* Method parameters in query string
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* Enum fields in path parameter (including repeated enum fields).
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* Mapping streaming APIs to newline-delimited JSON streams
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* Mapping HTTP headers with `Grpc-Metadata-` prefix to gRPC metadata (prefixed with `grpcgateway-`)
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* Optionally emitting API definition for [Swagger](http://swagger.io).
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* Setting [gRPC timeouts](http://www.grpc.io/docs/guides/wire.html) through inbound HTTP `Grpc-Timeout` header.
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### Want to support
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But not yet.
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* bytes fields in path parameter. #5
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* Optionally generating the entrypoint. #8
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* `import_path` parameter
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### No plan to support
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But patch is welcome.
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* Method parameters in HTTP headers
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* Handling trailer metadata
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* Encoding request/response body in XML
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* True bi-directional streaming. (Probably impossible?)
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# Mapping gRPC to HTTP
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* [How gRPC error codes map to HTTP status codes in the response](https://github.com/grpc-ecosystem/grpc-gateway/blob/master/runtime/errors.go#L15)
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* HTTP request source IP is added as `X-Forwarded-For` gRPC request header
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* HTTP request host is added as `X-Forwarded-Host` gRPC request header
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* HTTP `Authorization` header is added as `authorization` gRPC request header
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* Remaining Permanent HTTP header keys (as specified by the IANA [here](http://www.iana.org/assignments/message-headers/message-headers.xhtml) are prefixed with `grpcgateway-` and added with their values to gRPC request header
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* HTTP headers that start with 'Grpc-Metadata-' are mapped to gRPC metadata (prefixed with `grpcgateway-`)
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* While configurable, the default {un,}marshaling uses [jsonpb](https://godoc.org/github.com/golang/protobuf/jsonpb) with `OrigName: true`.
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# Contribution
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See [CONTRIBUTING.md](http://github.com/grpc-ecosystem/grpc-gateway/blob/master/CONTRIBUTING.md).
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# License
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grpc-gateway is licensed under the BSD 3-Clause License.
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See [LICENSE.txt](https://github.com/grpc-ecosystem/grpc-gateway/blob/master/LICENSE.txt) for more details.
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