gRPC-Gateway

gRPC to JSON proxy generator following the gRPC HTTP spec

## About

The gRPC-Gateway is a plugin of the Google protocol buffers compiler
[protoc](https://github.com/protocolbuffers/protobuf).
It reads protobuf service definitions and generates a reverse-proxy server which
translates a RESTful HTTP API into gRPC. This server is generated according to the
[`google.api.http`](https://github.com/googleapis/googleapis/blob/master/google/api/http.proto#L46)
annotations in your service definitions.

This helps you provide your APIs in both gRPC and RESTful style at the same time.

## Docs

You can read our docs at:

- https://grpc-ecosystem.github.io/grpc-gateway/

## Testimonials

> We use the gRPC-Gateway to serve millions of API requests per day,
> and have been since 2018 and through all of that,
> we have never had any issues with it.
>
> _- William Mill, [Ad Hoc](http://adhocteam.us/)_

## Background

gRPC is great -- it generates API clients and server stubs in many programming
languages, it is fast, easy-to-use, bandwidth-efficient and its design is
combat-proven by Google. However, you might still want to provide a traditional
RESTful JSON API as well. Reasons can range from maintaining
backward-compatibility, supporting languages or clients that are not well supported by
gRPC, to simply maintaining the aesthetics and tooling involved with a RESTful
JSON architecture.

This project aims to provide that HTTP+JSON interface to your gRPC service.
A small amount of configuration in your service to attach HTTP semantics is all
that's needed to generate a reverse-proxy with this library.

## Installation

### Compile from source

The following instructions assume you are using
[Go Modules](https://go.dev/wiki/Modules) for dependency
management. Use a
[tool dependency](https://go.dev/wiki/Modules#how-can-i-track-tool-dependencies-for-a-module)
to track the versions of the following executable packages:

```go
// +build tools

package tools

import (
    _ "github.com/grpc-ecosystem/grpc-gateway/v2/protoc-gen-grpc-gateway"
    _ "github.com/grpc-ecosystem/grpc-gateway/v2/protoc-gen-openapiv2"
    _ "google.golang.org/grpc/cmd/protoc-gen-go-grpc"
    _ "google.golang.org/protobuf/cmd/protoc-gen-go"
)
```

Run `go mod tidy` to resolve the versions. Install by running

```sh
go install \
    github.com/grpc-ecosystem/grpc-gateway/v2/protoc-gen-grpc-gateway \
    github.com/grpc-ecosystem/grpc-gateway/v2/protoc-gen-openapiv2 \
    google.golang.org/protobuf/cmd/protoc-gen-go \
    google.golang.org/grpc/cmd/protoc-gen-go-grpc
```

This will place four binaries in your `$GOBIN`;

- `protoc-gen-grpc-gateway`
- `protoc-gen-openapiv2`
- `protoc-gen-go`
- `protoc-gen-go-grpc`

Make sure that your `$GOBIN` is in your `$PATH`.

### **Using the `tool` Directive in Go 1.24**

Starting from Go 1.24, the `tool` directive in `go.mod` provides a structured way to track and manage executable dependencies. This replaces the previous workaround of using a separate `tools.go` file with blank imports.

#### **Tracking Tools in `go.mod`**

Instead of manually importing tool dependencies in a Go source file, you can now use the `tool` directive in `go.mod` to declare the tools your project depends on. For example:

```go
module tools

go 1.24

tool (
	github.com/grpc-ecosystem/grpc-gateway/v2/protoc-gen-grpc-gateway
	github.com/grpc-ecosystem/grpc-gateway/v2/protoc-gen-openapiv2
	google.golang.org/grpc/cmd/protoc-gen-go-grpc
	google.golang.org/protobuf/cmd/protoc-gen-go
)
```

#### **Managing Tool Dependencies**

To add tools to your module, use the `-tool` flag with `go get`:

```sh
go get -tool github.com/grpc-ecosystem/grpc-gateway/v2/protoc-gen-grpc-gateway
go get -tool github.com/grpc-ecosystem/grpc-gateway/v2/protoc-gen-openapiv2
go get -tool google.golang.org/protobuf/cmd/protoc-gen-go
go get -tool google.golang.org/grpc/cmd/protoc-gen-go-grpc
```

This automatically updates `go.mod`, adding the tools under the `tool` directive along with `require` statements to ensure version tracking.

### Install Tools

Once the tool dependencies are properly recorded in the `go.mod` file, simply execute the following command in the root directory of your project:

```sh
go install tool
```

This will place four binaries in your `$GOBIN`;

- `protoc-gen-grpc-gateway`
- `protoc-gen-openapiv2`
- `protoc-gen-go`
- `protoc-gen-go-grpc`

Make sure that your `$GOBIN` is in your `$PATH`.

### Download the binaries

You may alternatively download the binaries from the [GitHub releases page](https://github.com/grpc-ecosystem/grpc-gateway/releases/latest).
We generate [SLSA3 signatures](slsa.dev) using the OpenSSF's [slsa-framework/slsa-github-generator](https://github.com/slsa-framework/slsa-github-generator) during the release process. To verify a release binary:

1. Install the verification tool from [slsa-framework/slsa-verifier#installation](https://github.com/slsa-framework/slsa-verifier#installation).
2. Download the provenance file `attestation.intoto.jsonl` from the [GitHub releases page](https://github.com/grpc-ecosystem/grpc-gateway/releases/latest).
3. Run the verifier:

```shell
slsa-verifier -artifact-path <the-binary> -provenance attestation.intoto.jsonl -source github.com/grpc-ecosystem/grpc-gateway -tag <the-tag>
```

Alternatively, see the section on remotely managed plugin versions below.

## Usage

### 1.Define your [gRPC](https://grpc.io/docs/) service using protocol buffers

`your_service.proto`:

```protobuf
 syntax = "proto3";
 package your.service.v1;
 option go_package = "github.com/yourorg/yourprotos/gen/go/your/service/v1";

 message StringMessage {
   string value = 1;
 }

 service YourService {
   rpc Echo(StringMessage) returns (StringMessage) {}
 }
```

### 2. Generate gRPC stubs

This step generates the gRPC stubs that you can use to implement the service and consume from clients:

Here's an example `buf.gen.yaml` you can use to generate the stubs with [buf](https://github.com/bufbuild/buf):

```yaml
version: v2
plugins:
  - local: protoc-gen-go
    out: gen/go
    opt:
      - paths=source_relative
  - local: protoc-gen-go-grpc
    out: gen/go
    opt:
      - paths=source_relative
```

With this file in place, you can generate your files using `buf generate`.

> For a complete example of using `buf generate` to generate protobuf stubs, see
> [the boilerplate repo](https://github.com/johanbrandhorst/grpc-gateway-boilerplate).
> For more information on generating the stubs with buf, see
> [the official documentation](https://docs.buf.build/generate-usage).

If you are using `protoc` to generate stubs, here's an example of what a command
might look like:

```sh
protoc -I . \
    --go_out ./gen/go/ --go_opt paths=source_relative \
    --go-grpc_out ./gen/go/ --go-grpc_opt paths=source_relative \
    your/service/v1/your_service.proto
```

### 3. Implement your service in gRPC as usual.

### 4. Generate reverse-proxy using `protoc-gen-grpc-gateway`

At this point, you have 3 options:

- no further modifications, use the default mapping to HTTP semantics (method, path, etc.)
  - this will work on any `.proto` file, but will not allow setting HTTP paths, request parameters or similar
- additional `.proto` modifications to use a custom mapping
  - relies on parameters in the `.proto` file to set custom HTTP mappings
- no `.proto` modifications, but use an external configuration file
  - relies on an external configuration file to set custom HTTP mappings
  - mostly useful when the source proto file isn't under your control

#### 1. Using the default mapping

This requires no additional modification to the `.proto` file but does require enabling a specific option when executing the plugin.
The `generate_unbound_methods` should be enabled.

Here's what a `buf.gen.yaml` file might look like with this option enabled:

```yaml
version: v2
plugins:
  - local: protoc-gen-go
    out: gen/go
    opt:
      - paths=source_relative
  - local: protoc-gen-go-grpc
    out: gen/go
    opt:
      - paths=source_relative
  - local: protoc-gen-grpc-gateway
    out: gen/go
    opt:
      - paths=source_relative
      - generate_unbound_methods=true
```

With `protoc` (just the grpc-gateway stubs):

```sh
protoc -I . --grpc-gateway_out ./gen/go \
    --grpc-gateway_opt paths=source_relative \
    --grpc-gateway_opt generate_unbound_methods=true \
    your/service/v1/your_service.proto
```

#### 2. With custom annotations

Add a [`google.api.http`](https://github.com/googleapis/googleapis/blob/master/google/api/http.proto#L46)
annotation to your .proto file

`your_service.proto`:

```diff
 syntax = "proto3";
 package your.service.v1;
 option go_package = "github.com/yourorg/yourprotos/gen/go/your/service/v1";
+
+import "google/api/annotations.proto";
+
 message StringMessage {
   string value = 1;
 }

 service YourService {
-  rpc Echo(StringMessage) returns (StringMessage) {}
+  rpc Echo(StringMessage) returns (StringMessage) {
+    option (google.api.http) = {
+      post: "/v1/example/echo"
+      body: "*"
+    };
+  }
 }
```

> You will need to provide the required third party protobuf files to the protobuf compiler.
> If you are using [buf](https://github.com/bufbuild/buf), this dependency can
> be added to the `deps` array in your `buf.yaml` under the name
> `buf.build/googleapis/googleapis`:
>
> ```yaml
> version: v2
> name: buf.build/yourorg/myprotos
> deps:
>   - buf.build/googleapis/googleapis
> ```
>
> Always run `buf dep update` after adding a dependency to your `buf.yaml`.

See [a_bit_of_everything.proto](examples/internal/proto/examplepb/a_bit_of_everything.proto)
for examples of more annotations you can add to customize gateway behavior
and generated OpenAPI output.

Here's what a `buf.gen.yaml` file might look like:

```yaml
version: v2
plugins:
  - local: protoc-gen-go
    out: gen/go
    opt:
      - paths=source_relative
  - local: protoc-gen-go-grpc
    out: gen/go
    opt:
      - paths=source_relative
  - local: protoc-gen-grpc-gateway
    out: gen/go
    opt:
      - paths=source_relative
```

If you are using `protoc` to generate stubs, you need to ensure the required
dependencies are available to the compiler at compile time. These can be found
by manually cloning and copying the relevant files from the
[googleapis repository](https://github.com/googleapis/googleapis), and providing
them to `protoc` when running. The files you will need are:

```
google/api/annotations.proto
google/api/field_behavior.proto
google/api/http.proto
google/api/httpbody.proto
```

Here's what a `protoc` execution might look like:

```sh
protoc -I . --grpc-gateway_out ./gen/go \
    --grpc-gateway_opt paths=source_relative \
    your/service/v1/your_service.proto
```

#### 3. External configuration

If you do not want to (or cannot) modify the proto file for use with gRPC-Gateway you can
alternatively use an external
[gRPC Service Configuration](https://cloud.google.com/endpoints/docs/grpc/grpc-service-config) file.
[Check our documentation](https://grpc-ecosystem.github.io/grpc-gateway/docs/mapping/grpc_api_configuration/)
for more information. This is best combined with the `standalone=true` option
to generate a file that can live in its own package, separate from the files
generated by the source protobuf file.

Here's what a `buf.gen.yaml` file might look like with this option enabled:

```yaml
version: v2
plugins:
  - local: protoc-gen-go
    out: gen/go
    opt:
      - paths=source_relative
  - local: protoc-gen-go-grpc
    out: gen/go
    opt:
      - paths=source_relative
  - local: protoc-gen-grpc-gateway
    out: gen/go
    opt:
      - paths=source_relative
      - grpc_api_configuration=path/to/config.yaml
      - standalone=true
```

With `protoc` (just the grpc-gateway stubs):

```sh
protoc -I . --grpc-gateway_out ./gen/go \
    --grpc-gateway_opt paths=source_relative \
    --grpc-gateway_opt grpc_api_configuration=path/to/config.yaml \
    --grpc-gateway_opt standalone=true \
    your/service/v1/your_service.proto
```

### 5. Write an entrypoint for the HTTP reverse-proxy server

```go
package main

import (
  "context"
  "flag"
  "net/http"

  "github.com/grpc-ecosystem/grpc-gateway/v2/runtime"
  "google.golang.org/grpc"
  "google.golang.org/grpc/credentials/insecure"
  "google.golang.org/grpc/grpclog"

  gw "github.com/yourorg/yourrepo/proto/gen/go/your/service/v1/your_service"  // Update
)

var (
  // command-line options:
  // gRPC server endpoint
  grpcServerEndpoint = flag.String("grpc-server-endpoint",  "localhost:9090", "gRPC server endpoint")
)

func run() error {
  ctx := context.Background()
  ctx, cancel := context.WithCancel(ctx)
  defer cancel()

  // Register gRPC server endpoint
  // Note: Make sure the gRPC server is running properly and accessible
  mux := runtime.NewServeMux()
  opts := []grpc.DialOption{grpc.WithTransportCredentials(insecure.NewCredentials())}
  err := gw.RegisterYourServiceHandlerFromEndpoint(ctx, mux,  *grpcServerEndpoint, opts)
  if err != nil {
    return err
  }

  // Start HTTP server (and proxy calls to gRPC server endpoint)
  return http.ListenAndServe(":8081", mux)
}

func main() {
  flag.Parse()

  if err := run(); err != nil {
    grpclog.Fatal(err)
  }
}
```

### 6. (Optional) Generate OpenAPI definitions using `protoc-gen-openapiv2`

Here's what a `buf.gen.yaml` file might look like:

```yaml
version: v2
plugins:
  - local: protoc-gen-go
    out: gen/go
    opt:
      - paths=source_relative
  - local: protoc-gen-go-grpc
    out: gen/go
    opt:
      - paths=source_relative
  - local: protoc-gen-grpc-gateway
    out: gen/go
    opt:
      - paths=source_relative
      - generate_unbound_methods=true
  - local: protoc-gen-openapiv2
    out: gen/go
```

To use the custom protobuf annotations supported by `protoc-gen-openapiv2`, we need
another dependency added to our protobuf generation step. If you are using
`buf`, you can add the `buf.build/grpc-ecosystem/grpc-gateway` dependency
to your `deps` array:

```yaml
version: v2
name: buf.build/yourorg/myprotos
deps:
  - buf.build/googleapis/googleapis
  - buf.build/grpc-ecosystem/grpc-gateway
```

With `protoc` (just the swagger file):

```sh
protoc -I . --openapiv2_out ./gen/openapiv2 \
    your/service/v1/your_service.proto
```

If you are using `protoc` to generate stubs, you will need to copy the protobuf
files from the `protoc-gen-openapiv2/options` directory of this repository,
and providing them to `protoc` when running.

Note that this plugin also supports generating OpenAPI definitions for unannotated methods;
use the `generate_unbound_methods` option to enable this.

It is possible with the HTTP mapping for a gRPC service method to create duplicate mappings
with the only difference being constraints on the path parameter.

`/v1/{name=projects/*}` and `/v1/{name=organizations/*}` both become `/v1/{name}`. When
this occurs the plugin will rename the path parameter with a "\_1" (or "\_2" etc) suffix
to differentiate the different operations. So in the above example, the 2nd path would become
`/v1/{name_1=organizations/*}`. This can also cause OpenAPI clients to URL encode the "/" that is
part of the path parameter as that is what OpenAPI defines in the specification. To allow gRPC gateway to
accept the URL encoded slash and still route the request, use the UnescapingModeAllCharacters or
UnescapingModeLegacy (which is the default currently though may change in future versions). See
[Customizing Your Gateway](https://grpc-ecosystem.github.io/grpc-gateway/docs/mapping/customizing_your_gateway/)
for more information.

## Usage with remote plugins

As an alternative to all of the above, you can use `buf` with
[remote plugins](https://buf.build/docs/bsr/remote-plugins/usage)
to manage plugin versions and generation. An example `buf.gen.yaml` using remote
plugin generation looks like this:

```yaml
version: v2
plugins:
  - remote: buf.build/protocolbuffers/go:v1.31.0
    out: gen/go
    opt:
      - paths=source_relative
  - remote: buf.build/grpc/go:v1.3.0
    out: gen/go
    opt:
      - paths=source_relative
  - remote: buf.build/grpc-ecosystem/gateway:v2.16.2
    out: gen/go
    opt:
      - paths=source_relative
  - remote: buf.build/grpc-ecosystem/openapiv2:v2.16.2
    out: gen/openapiv2
```

This requires no local installation of any plugins. Be careful to use the same
version of the generator as the runtime library, i.e. if using `v2.16.2`, run

```shell
$ go get github.com/grpc-ecosystem/grpc-gateway/v2@v2.16.2
```

To get the same version of the runtime in your `go.mod`.

Note that usage of remote plugins is incompatible with usage of external configuration files like [grpc_api_configuration](https://grpc-ecosystem.github.io/grpc-gateway/docs/mapping/grpc_api_configuration/#using-an-external-configuration-file).

## Video intro

This GopherCon UK 2019 presentation from our maintainer [@JohanBrandhorst](https://github.com/johanbrandhorst) provides a good intro to using the gRPC-Gateway. It uses the following boilerplate repo as a base: https://github.com/johanbrandhorst/grpc-gateway-boilerplate.

## Parameters and flags

When using `buf` to generate stubs, flags and parameters are passed through
the `opt` field in your `buf.gen.yaml` file, for example:

```yaml
version: v2
plugins:
  - local: protoc-gen-grpc-gateway
    out: gen/go
    opt:
      - paths=source_relative
      - grpc_api_configuration=path/to/config.yaml
      - standalone=true
```

During code generation with `protoc`, flags to gRPC-Gateway tools must be passed
through `protoc` using one of 2 patterns:

- as part of the `--<tool_suffix>_out` `protoc` parameter: `--<tool_suffix>_out=<flags>:<path>`

```sh
--grpc-gateway_out=repeated_path_param_separator=ssv:.
--openapiv2_out=repeated_path_param_separator=ssv:.
```

- using additional `--<tool_suffix>_opt` parameters: `--<tool_suffix>_opt=<flag>[,<flag>]*`

```sh
--grpc-gateway_opt repeated_path_param_separator=ssv
--openapiv2_opt repeated_path_param_separator=ssv
```

## More examples

More examples are available under the `examples` directory.

- `proto/examplepb/echo_service.proto`, `proto/examplepb/a_bit_of_everything.proto`, `proto/examplepb/unannotated_echo_service.proto`: service definition
  - `proto/examplepb/echo_service.pb.go`, `proto/examplepb/a_bit_of_everything.pb.go`, `proto/examplepb/unannotated_echo_service.pb.go`: [generated] stub of the service
  - `proto/examplepb/echo_service.pb.gw.go`, `proto/examplepb/a_bit_of_everything.pb.gw.go`, `proto/examplepb/uannotated_echo_service.pb.gw.go`: [generated] reverse proxy for the service
  - `proto/examplepb/unannotated_echo_service.yaml`: gRPC API Configuration for `unannotated_echo_service.proto`
- `server/main.go`: service implementation
- `main.go`: entrypoint of the generated reverse proxy

To use the same port for custom HTTP handlers (e.g. serving `swagger.json`),
gRPC-Gateway, and a gRPC server, see
[this example by CoreOS](https://github.com/philips/grpc-gateway-example/blob/master/cmd/serve.go)
(and its accompanying [blog post](https://web.archive.org/web/20201112010739/https://coreos.com/blog/grpc-protobufs-swagger.html)).

[This example by neiro.ai](https://github.com/mynalabsai/grpc_gateway_media_example) (and its accompanying [blog post](https://medium.com/neiro-ai/grpc-gateway-for-media-api-by-neiro-9033caab12c8)) shows how mediafiles using `multipart/form-data` can be integrated into rpc messages using a middleware.

## Features

### Supported

- Generating JSON API handlers.
- Method parameters in the request body.
- Method parameters in the request path.
- Method parameters in the query string.
- Enum fields in the path parameter (including repeated enum fields).
- Mapping streaming APIs to newline-delimited JSON streams.
- Mapping HTTP headers with `Grpc-Metadata-` prefix to gRPC metadata (prefixed with `grpcgateway-`)
- Optionally emitting API definitions for
  [OpenAPI (Swagger) v2](https://swagger.io/docs/specification/2-0/basic-structure/).
- Setting [gRPC timeouts](https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests)
  through inbound HTTP `Grpc-Timeout` header.
- Partial support for [gRPC API Configuration](https://cloud.google.com/endpoints/docs/grpc/grpc-service-config)
  files as an alternative to annotation.
- Automatically translating PATCH requests into Field Mask gRPC requests. See
  [the docs](https://grpc-ecosystem.github.io/grpc-gateway/docs/mapping/patch_feature/)
  for more information.

### No plan to support

But patches are welcome.

- Method parameters in HTTP headers.
- Handling trailer metadata.
- Encoding request/response body in XML.
- True bi-directional streaming.

## Mapping gRPC to HTTP

- [How gRPC error codes map to HTTP status codes in the response](https://github.com/grpc-ecosystem/grpc-gateway/blob/main/runtime/errors.go#L15).
- HTTP request source IP is added as `X-Forwarded-For` gRPC request header.
- HTTP request host is added as `X-Forwarded-Host` gRPC request header.
- HTTP `Authorization` header is added as `authorization` gRPC request header.
- 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.
- HTTP headers that start with 'Grpc-Metadata-' are mapped to gRPC metadata
  (prefixed with `grpcgateway-`).
- While configurable, the default {un,}marshaling uses
  [protojson](https://pkg.go.dev/google.golang.org/protobuf/encoding/protojson).
- The path template used to map gRPC service methods to HTTP endpoints supports the [google.api.http](https://github.com/googleapis/googleapis/blob/master/google/api/http.proto)
  path template syntax. For example, `/api/v1/{name=projects/*/topics/*}` or `/prefix/{path=organizations/**}`.

## Contribution

See [CONTRIBUTING.md](http://github.com/grpc-ecosystem/grpc-gateway/blob/main/CONTRIBUTING.md).

## License

gRPC-Gateway is licensed under the BSD 3-Clause License.
See [LICENSE](https://github.com/grpc-ecosystem/grpc-gateway/blob/main/LICENSE) for more details.
