GitHub Actions	CircleCI

Overview

This is an example of a golang-based monorepo. It has the following features:

• Only build the services or cmds that are modified in a commit;
• Build all services and/or cmds that are affected by changes in common codes (i.e. pkg);
• Build all services and/or cmds that are affected by changes in vendor codes.

For now, CircleCI 2.1 and GitHub Actions are supported. But since it uses bash scripts and Makefiles, it should be fairly straightforward to port to TravisCI or AppVeyor, etc.

At the moment, CI is setup with GO111MODULE=on and GOFLAGS=-mod=vendor environment variables enabled during build. See sample dockerfile for more details.

How does it work

During CI builds, build.sh iterates the updated files within the commit range (CIRCLE_COMPARE_URL environment variable in CircleCI) or the modified files within a single commit (when the value is not a valid range), excluding hidden files, pkg, and vendor folders. It will then try to walk up the directory path until it can find a Makefile (excluding root Makefile). Once found, the root Makefile will include that Makefile and call the custom rule as target, thus, initiating the build.

When the changes belong to either pkg or vendor, the script will then try to determine the services (and cmds) that have dependencies using the go list command. All dependent services will then be built using the same process described above.

You can override the COMMIT_RANGE environment variable for your own CI. If this is set, build.sh will use its value. You also want to set CIRCLE_SHA1 to your commit SHA (CIRCLE_SHA1 is CircleCI-specific). Example for GitHub Actions is here. Something like:

# If your commit range is correct:
COMMIT_RANGE: aaaaa..bbbbb
CIRCLE_SHA1: aaaaa

# If no valid commit range:
COMMIT_RANGE: <your_commit_sha>
CIRCLE_SHA1: <your_commit_sha>

Directory structure

• services/ - Basically, long running services.
• cmd/ - CLI-based tools that are not long running.
• pkg/ - Shared codes, or libraries common across the repo.
• vendor/ - Third party codes from different vendors.

Although we have this structure, there is no limitation into where should you put your services/cmds. Any subdirectory structure is fine as long as a Makefile is provided.

How to add a service/cmd

A reference template named samplesvc is provided. Basically, these are the things that you need to do:

• Create a new directory for your service under services/ or tool under cmd/. You may copy the samplesvc contents to your new directory.
• Update the dockerfile inside your new service directory. Note that during build, this dockerfile is copied to the root directory (to be able to access pkg and vendor directories).
• Update the Makefile with your own values. You need to at least update the MODULE variable with your service name. The only required rule is the custom part so you may need to change that as well (i.e. name of the dockerfile used in docker build).
• [Optional] Update the deploy.sh script for your deployment needs.