The gRPC-Gateway is a plugin of the Google protocol buffers compiler
protoc.
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
annotations in your service definitions.
This helps you provide your APIs in both gRPC and RESTful style at the same time.
You can read our docs at:
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
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.
The following instructions assume you are using Go Modules for dependency management. Use a tool dependency to track the versions of the following executable packages:
// +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
$ 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-grpcThis will place four binaries in your $GOBIN;
protoc-gen-grpc-gatewayprotoc-gen-openapiv2protoc-gen-goprotoc-gen-go-grpc
Make sure that your $GOBIN is in your $PATH.
You may alternatively download the binaries from the GitHub releases page. We generate SLSA3 signatures using the OpenSSF's slsa-framework/slsa-github-generator during the release process. To verify a release binary:
- Install the verification tool from slsa-framework/slsa-verifier#installation.
- Download the provenance file
attestation.intoto.jsonlfrom the GitHub releases page. - Run the verifier:
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.
1.Define your gRPC service using protocol buffers
your_service.proto:
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) {}
}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:
version: v1
plugins:
- plugin: go
out: gen/go
opt:
- paths=source_relative
- plugin: go-grpc
out: gen/go
opt:
- paths=source_relativeWith this file in place, you can generate your files using buf generate.
For a complete example of using
buf generateto generate protobuf stubs, see the boilerplate repo. For more information on generating the stubs with buf, see the official documentation.
If you are using protoc to generate stubs, here's an example of what a command
might look like:
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.protoAt this point, you have 3 options:
- no further modifications, use the default mapping to HTTP semantics (method, path, etc.)
- this will work on any
.protofile, but will not allow setting HTTP paths, request parameters or similar
- this will work on any
- additional
.protomodifications to use a custom mapping- relies on parameters in the
.protofile to set custom HTTP mappings
- relies on parameters in the
- no
.protomodifications, 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
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:
version: v1
plugins:
- plugin: go
out: gen/go
opt:
- paths=source_relative
- plugin: go-grpc
out: gen/go
opt:
- paths=source_relative
- plugin: grpc-gateway
out: gen/go
opt:
- paths=source_relative
- generate_unbound_methods=trueWith protoc (just the grpc-gateway stubs):
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.protoAdd a google.api.http
annotation to your .proto file
your_service.proto:
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, this dependency can be added to the
depsarray in yourbuf.yamlunder the namebuf.build/googleapis/googleapis:version: v1 name: buf.build/yourorg/myprotos deps: - buf.build/googleapis/googleapisAlways run
buf mod updateafter adding a dependency to yourbuf.yaml.
See 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:
version: v1
plugins:
- plugin: go
out: gen/go
opt:
- paths=source_relative
- plugin: go-grpc
out: gen/go
opt:
- paths=source_relative
- plugin: grpc-gateway
out: gen/go
opt:
- paths=source_relativeIf 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, 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:
protoc -I . --grpc-gateway_out ./gen/go \
--grpc-gateway_opt paths=source_relative \
your/service/v1/your_service.protoIf 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 file.
Check our documentation
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:
version: v1
plugins:
- plugin: go
out: gen/go
opt:
- paths=source_relative
- plugin: go-grpc
out: gen/go
opt:
- paths=source_relative
- plugin: grpc-gateway
out: gen/go
opt:
- paths=source_relative
- grpc_api_configuration=path/to/config.yaml
- standalone=trueWith protoc (just the grpc-gateway stubs):
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.protopackage 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)
}
}Here's what a buf.gen.yaml file might look like:
version: v1
plugins:
- plugin: go
out: gen/go
opt:
- paths=source_relative
- plugin: go-grpc
out: gen/go
opt:
- paths=source_relative
- plugin: grpc-gateway
out: gen/go
opt:
- paths=source_relative
- plugin: openapiv2
out: gen/openapiv2To 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:
version: v1
name: buf.build/yourorg/myprotos
deps:
- buf.build/googleapis/googleapis
- buf.build/grpc-ecosystem/grpc-gatewayWith protoc (just the swagger file):
protoc -I . --openapiv2_out ./gen/openapiv2 \
your/service/v1/your_service.protoIf 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
for more information.
As an alternative to all of the above, you can use buf with
remote plugins
to manage plugin versions and generation. An example buf.gen.yaml using remote
plugin generation looks like this:
version: v1
plugins:
- plugin: buf.build/protocolbuffers/go:v1.31.0
out: gen/go
opt:
- paths=source_relative
- plugin: buf.build/grpc/go:v1.3.0
out: gen/go
opt:
- paths=source_relative
- plugin: buf.build/grpc-ecosystem/gateway:v2.16.2
out: gen/go
opt:
- paths=source_relative
- plugin: buf.build/grpc-ecosystem/openapiv2:v2.16.2
out: gen/openapiv2This 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
$ go get github.com/grpc-ecosystem/grpc-gateway/[email protected]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.
This GopherCon UK 2019 presentation from our maintainer @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.
When using buf to generate stubs, flags and parameters are passed through
the opt field in your buf.gen.yaml file, for example:
version: v1
plugins:
- plugin: grpc-gateway
out: gen/go
opt:
- paths=source_relative
- grpc_api_configuration=path/to/config.yaml
- standalone=trueDuring 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>_outprotocparameter:--<tool_suffix>_out=<flags>:<path>
--grpc-gateway_out=repeated_path_param_separator=ssv:.
--openapiv2_out=repeated_path_param_separator=ssv:.- using additional
--<tool_suffix>_optparameters:--<tool_suffix>_opt=<flag>[,<flag>]*
--grpc-gateway_opt repeated_path_param_separator=ssv
--openapiv2_opt repeated_path_param_separator=ssvMore 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 definitionproto/examplepb/echo_service.pb.go,proto/examplepb/a_bit_of_everything.pb.go,proto/examplepb/unannotated_echo_service.pb.go: [generated] stub of the serviceproto/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 serviceproto/examplepb/unannotated_echo_service.yaml: gRPC API Configuration forunannotated_echo_service.proto
server/main.go: service implementationmain.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
(and its accompanying blog post).
This example by neiro.ai (and its accompanying blog post) shows how mediafiles using multipart/form-data can be integrated into rpc messages using a middleware.
- 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 withgrpcgateway-) - Optionally emitting API definitions for OpenAPI (Swagger) v2.
- Setting gRPC timeouts
through inbound HTTP
Grpc-Timeoutheader. - Partial support for gRPC API Configuration files as an alternative to annotation.
- Automatically translating PATCH requests into Field Mask gRPC requests. See the docs for more information.
But patches are welcome.
- Method parameters in HTTP headers.
- Handling trailer metadata.
- Encoding request/response body in XML.
- True bi-directional streaming.
- How gRPC error codes map to HTTP status codes in the response.
- HTTP request source IP is added as
X-Forwarded-ForgRPC request header. - HTTP request host is added as
X-Forwarded-HostgRPC request header. - HTTP
Authorizationheader is added asauthorizationgRPC request header. - Remaining Permanent HTTP header keys (as specified by the IANA
here)
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.
- The path template used to map gRPC service methods to HTTP endpoints supports the google.api.http
path template syntax. For example,
/api/v1/{name=projects/*/topics/*}or/prefix/{path=organizations/**}.
See CONTRIBUTING.md.
gRPC-Gateway is licensed under the BSD 3-Clause License. See LICENSE for more details.
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