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* adding missing arguments, fixing entrypoint bugs, adding tests

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gRPC/Protocol Buffer Compiler Containers

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This repository contains support for various Docker images that wrap protoc, prototool, grpc_cli commands with gRPC support in a variety of languages removing the need to install and manage these commands locally. It relies on setting a simple volume to the docker container, usually mapping the current directory to /defs, and specifying the file and language you want to generate.


  • Docker images for:
    • protoc with namely/protoc (automatically includes /usr/local/include)
    • Uber's Prototool with namely/prototool
    • A custom generation script to facilitate common use-cases with namely/protoc-all (see below)
    • grpc_cli with namely/grpc-cli
    • gRPC Gateway using a custom go-based server with namely/gen-grpc-gateway
  • Google APIs included in /opt/include/google
  • Protobuf library artifacts included in /opt/include/google/protobuf. NOTE: protoc would only need part of the path i.e. -I /opt/include if you import WKTs like so:
import "google/protobuf/empty.proto";
  • Support for all C-based gRPC libraries with Go and Java native libraries

If you're having trouble, see Docker troubleshooting below.

Note - throughout this document, commands for bash are prefixed with $ and commands for PowerShell on Windows are prefixed with PS>. It is not required to use "Windows Subsystem for Linux" (WSL) except for development work on docker-protoc itself

Tag Conventions

For protoc, grpc_cli and prototool a pattern of <GRPC_VERSION>_<CONTAINER_VERSION> is used for all images (or <GRPC_VERSION>_<CONTAINER_VERSION>-rc.<PRERELEASE_NUMBER>) for pre-releases). Example is namely/protoc-all:1.15_0 for gRPC version 1.15 (or namely/protoc-all:1.15_0-rc.1 for a pre-release). The latest tag will always point to the most recent version.


Pull the container:

$ docker pull namely/protoc-all

After that, change working directory to the one that contains your .proto definition files.

So if you have a directory: ~/my_project/protobufs/ that has: myproto.proto, you'd want to run this:

$ cd ~/my_project/protobufs
$ docker run -v $PWD:/defs namely/protoc-all -f myproto.proto -l ruby #or go, csharp, etc
PS> cd ~/my_project/protobufs
PS> docker run -v ${pwd}:/defs namely/protoc-all -f myproto.proto -l ruby #or go, csharp, etc

The container automatically puts the compiled files into a gen directory with language-specific sub-directories. So for Golang, the files go into a directory ./gen/pb-go; For ruby the directory is ./gen/pb-ruby.


You can use the -o flag to specify an output directory. This will automatically be created. For example, add -o my-gen to add all fileoutput to the my-gen directory. In this case, pb-* subdirectories will not be created.

You can use the -d flag to generate all proto files in a directory. You cannot use this with the -f option.

You can also use -i to add extra include directories. This can be helpful to lift protofiles up a directory when generating. As an example, say you have a file protorepo/catalog/catalog.proto. This will by default output to gen/pb-go/protorepo/catalog/ because protorepo is part of the file path input. To remove the protorepo you need to add an include and change the import:

$ docker run ... namely/protoc-all -i protorepo -f catalog/catalog.proto -l go
# instead of
$ docker run ... namely/protoc-all -f protorepo/catalog/catalog.proto -l go
# which will generate files in a `protorepo` directory.

Ruby-specific options

--with-rbi to generate Ruby Sorbet type definition .rbi files

node/web-specific options

--js-out <string> to modify the js_out= options for node and web code generation

--grpc-web-out <string> to modify the grpc-web_out= options for web code generation

--grpc-out <string> to modify the grpc_out= options for node and web code generation. See for more details.

gRPC Gateway

This repo also provides a docker image namely/gen-grpc-gateway to generate a grpc-gateway server. By annotating your proto (see the grpc-gateway documentation), you can generate a server that acts as an HTTP server, and a gRPC client to your gRPC service.

Generate a gRPC Gateway docker project with

docker run -v `pwd`:/defs namely/gen-grpc-gateway -f path/to/your/proto.proto -s Service

where Service is the name of your gRPC service defined in the proto. This will create a folder with a simple go server. By default, this goes in the gen/grpc-gateway folder. You can then build the contents of this folder into an actual runnable grpc-gateway server.

Build your gRPC Gateway server with

docker build -t my-grpc-gateway gen/grpc-gateway/

NOTE: If your service does not contain any (google.api.http) annotations, this build will fail with an error ...HandlerFromEndpoint is undefined. You need to have at least one rpc method annotated to build a gRPC Gateway, or use --generate-unbound-methods option to expose all the methods in your proto file

Run this image with

docker run my-grpc-gateway --backend=grpc-service:50051

where --backend refers to your actual gRPC server's address. The gRPC gateway listens on port 80 for HTTP traffic.

Configuring grpc-gateway

The gateway is configured using spf13/viper, see gwy/templates/config.yaml.tmpl for configuration options.

To configure your gateway to run under a prefix, set proxy.api-prefix to that prefix. For example, if you have (google.api.http) = '/foo/bar', and set proxy.api-prefix to /api/', your gateway will listen to requests on '/api/foo/bar'. This can also be set with the environment variable <SERVICE>_PROXY_API-PREFIX where <SERVICE> is the name of the service generating the gateway.

See gwy/ for an example of how to set the prefix with an environment variable.

HTTP Headers

The gateway will turn any HTTP headers that it receives into gRPC metadata. Any permanent HTTP headers will be prefixed with grpcgateway- in the metadata, so that your server receives both the HTTP client-to-gateway headers, as well as the gateway-to-gRPC server headers.

Any headers starting with Grpc- will be prefixed with an X-; this is because grpc- is a reserved metadata prefix.

All other headers will be converted to metadata as-is.

CORS Configuration

You can configure CORS for your gateway through the configuration. This will allow your gateway to receive requests from different origins.

There are four values:

  • cors.allow-origin: Value to set for Access-Control-Allow-Origin header.
  • cors.allow-credentials: Value to set for Access-Control-Allow-Credentials header.
  • cors.allow-methods: Value to set for Access-Control-Allow-Methods header.
  • cors.allow-headers: Value to set for Access-Control-Allow-Headers header.

For CORS, you will want to configure your cors.allow-methods to be the HTTP verbs set in your proto (i.e. GET, PUT, etc.), as well as OPTIONS, so that your service can handle the preflight request.

If you are not using CORS, you can leave these configuration values at their default, and your gateway will not accept CORS requests.

GRPC Client Configuration

  • grpc.max-call-recv-msg-size: Sets the maximum message size in bytes the client can receive.

  • grpc.max-call-send-msg-size: Sets the maximum message size in bytes the client can send.

Other Response Headers

You can configure additional headers to be sent in the HTTP response. Set environment variable with prefix <SERVICE>_RESPONSE-HEADERS_ (e.g SOMESERVICE_RESPONSE-HEADERS_SOME-HEADER-KEY). You can also set headers in the your configuration file (e.g response-headers.some-header-key)

Marshalling options

Setting Marshaler version

By default, gen-grpc-gateway will use a marshaler/unmarshaler based on jsonpb. You can change this behavior by setting gateway.use-jsonpb-v2-marshaler: true, which will use protojson - a newer version which is more aligned with proto <=> json mapping.

Proto names format

By default, gen-grpc-gateway will return proto names as they are in the proto messages. You can change this behavior by setting gateway.use-json-names: true and the gateway will use camelCase JSON names.

Unpopulated fields

By default, gen-grpc-gateway will not emit unpopulated fields. You can change this behavior by setting gateway.emit-unpopulated: true and the gateway will populate these fields with default values.

Unknown fields

By default, gen-grpc-gateway will discard unknown fields from requests. You can change this behavior by setting gateway.keep-unknown: true and the gateway will keep these fields in the requests.

Environment Variables

The gateway project used spf13/viper for configuration. The generated gateway code includes a config file that can be overridden with cli flags or environment variables. For environment-variable overrides, use a <SERVICE>_ prefix, upcase the setting, and replace . with _.


This repo also contains a Dockerfile for building a grpc_cli.

Run it with

docker run -v `pwd`:/defs --rm -it namely/grpc-cli call docker.for.mac.localhost:50051 \\
LinkShortener.ResolveShortLink "short_link:'asdf'" --protofiles=link_shortener.proto

You can pass multiple files to --protofiles by separating them with commas, for example --protofiles=link_shortener.proto,foo/bar/baz.proto,biz.proto. All of the protofiles must be relative to pwd, since pwd is mounted into the container.

See the grpc_cli documentation for more information. You may find it useful to bind this to an alias:

alias grpc_cli='docker run -v $PWD:/defs --rm -it namely/grpc-cli'

Note the use of single quotes in the alias, which avoids expanding the $PWD parameter when the alias is created.

Now you can call it with

grpc_cli call docker.for.mac.localhost:50051 LinkShortener.ResolveShortLink "short_link:'asdf'" --protofiles=link_shortener.proto


Thank you for considering a contribution to namely/docker-protoc!

If you'd like to make an enhancement, or add a container for another language compiler, you will need to run one of the build scripts in this repo. You will also need to be running Mac, Linux, or WSL 2, and have Docker installed.


From the repository root, run this command to build all the known containers:

make build

Note the version tag in Docker's console output - this image tag is required to run the tests using the container with your changes.

You can change some environment variables relevant to the build by setting them as prefixes to the make command. For example, this would build the containers using Node.js 15 and gRPC 1.35. See some interesting variables in and

NODE_VERSION=15 GRPC_VERSION=1.35 make build


Running tests for protoc-all image

To run the tests, identify your image tag from the build step and run make test as below:

CONTAINER=namely/protoc-all:VVV make test

(VVV is your version from the tag in the console output when running make build.) Running this will demonstrate that your new image can successfully build containers for each language.

Note that testing currently requires Go to be locally installed.

Adding tests

The tests for protoc-all are written in Go.
To add or modify tests, use the testCase struct in all_test.go to set: the language, the arguments to invoke the image with, the expected generated files and any additional assertions.

gRPC Gateway test

CONTAINER=namely/gen-grpc-gateway:VVV make test-gwy

Auto Dependency Managenement

Dependencies are managed in this repo via Renovate. Please read more here.


Any new gRPC version based release is handled automatically once the relevant Renovate branch is merged to master via the CI (Github Action). A patch release should be created manually in Github and the CI workflow will take care of the rest.


Open a PR and ping one of the Namely employees who have worked on this repo recently. We will take a look as soon as we can.
Thank you!!

Namely Employees

Namely employees can merge PRs and cut a release/pre-release by drafting a new Github release and publishing them.
The release name should follow the same tag conventions described in this doc and the gRPC version in the release name
must match the GRPC_VERSION configured in
A valid release/pre-release will be of the form v${GRPC_VERSION}_${BUILD_VERSION}/v${GRPC_VERSION}_${BUILD_VERSION}-rc.${RC_VERSION} respectively.
e.g 1.37_2, 1.38_0-rc.3.
Once a new valid Github release is published, new images will be published to DockerHub via CI.

Docker Troubleshooting

Docker must be configured to use Linux containers.

If on Windows, you must have your C: drive shared with Docker. Open the Docker settings (right-click Docker icon in notification area) and pick the Shared Drives tab. Ensure C: is listed and the box is checked. If you are still experiencing trouble, click "Reset credentials..." on that tab and re-enter your local Windows username and password.