This tool defines a custom build step that allows the Cloud Build worker to run the protocol buffer compiler, protoc.

When to use this builder

The gcr.io/cloud-builders/protoc build step should be used when you want to run protoc. It may be used as part of a Google Cloud Build process.

Building this builder

You will need to build this Builder and push it to a container registry before you may use it. To build and push to Google Container Registry, run the following command in this directory:

gcloud builds submit . --config=cloudbuild.yaml

If you wish to specify a different version or architecture for the build, run the following:

gcloud builds submit . --config=cloudbuild.yaml --substitutions=_VERS=${VERS},_ARCH=${ARCH}

Where ${VERS} and ${ARCH} are defined to contain values for the release and architecture as listed on:

https://github.com/protocolbuffers/protobuf/releases

NB Due to inconsistent handling of URLs for release candidates, the build will fail when referencing these (issue).

Referencing protoc compiler plugins

It is common to augment protoc with language-specific compiler plugins. Here is a list of plugins:

https://github.com/protocolbuffers/protobuf/blob/master/docs/third_party.md

These plugins take the form protoc-gen-[[NAME]]. For example, the plugin to generate Golang is called protoc-gen-go

The usual command takes the form:

protoc \
--proto-path=... \
- --go_out=plugins=grpc:...

But this assumes that protoc-gen-go is accessible in ${PATH} and configuring ${PATH} is challenging across containers.

The solution is to install the compiler plugins either to /workspace or using volumes: and then reference it using --plugin

E.g.:

- name: gcr.io/${PROJECT_ID}/protoc
  args:
  - --proto_path=...
  - --plugin=protoc-gen-go=/workspace/plugins/protoc-gen-go
  - --go_out=plugins=grpc:...
    - /workspace/protos/my.proto

In this example, protoc-gen-go must have been installed during a previous step into /workspace/plugins.