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Go build

This document describes the Go code layout and build integration with Gradle. The setup is non-trivial, because the Go toolchain expects a certain layout and Gradle support is limited.

Goals:

  1. Go code can be built and tested using Gradle w/o special requirements.
  2. Go tools such as go build, go test and go generate work as usual.
  3. Go code can be pulled with go get from github.com/apache/beam for users.
  4. Go programs can used in docker container images.

In short, the goals are to make both worlds work well.

Gradle integration

The Go toolchain expects the package name to match the directory structure, which in turn must be rooted in github.com/apache/beam for go get to work. This directory prefix is beyond the repo itself and we must copy the Go source code into such a layout to invoke the tool chain. We use a single directory sdks/go for all shared library code and export it as a zip file during the build process to be used by various tools, such as sdks/java/container. This scheme balances the convenience of combined Go setup with the desire for a unified layout across languages. Python seems to do the same.

The container build adds a small twist to the build integration, because container images use linux/amd64 but the development setup might not. We therefore additionally cross-compile Go binaries for inclusion into container images where needed, generally placed in target/linux_amd64.

Go development setup

Developers must clone their git repository into:

$GOPATH/src/github.com/apache

to match the package structure expected by the code imports. Go users can just go get the code directly. For example:

go get github.com/apache/beam/sdks/go/...

Developers must invoke Go for cross-compilation manually, if desired.

If you make changes to .proto files, you will need to rebuild the generated code. Consult pkg/beam/model/PROTOBUF.md.