Deploy individual services from a monorepo using github actions - github

Question

I have around 10 individual micro-services which are mostly cloud functions for various data processing jobs, which all live in a single github repository.
The goal is to trigger the selective deployment of these service to Google Cloud Functions, on push to a branch - when an individual function has been updated.
I must avoid the situation in which update of a single service causes the deployment of all the cloud functions.
My current repository structure:
/repo
--/service_A
----/function
----/notebook
--/service_B
----/function
----/notebook
On a side note, what are the pros/cons of using Github Actions VS Google Cloud Build for such automation?

Answer 1

GitHub Actions supports monorepos with path filtering for workflows. You can create a workflow to selectively trigger when files on a specific path change.
https://help.github.com/en/articles/workflow-syntax-for-github-actions#onpushpull_requestpaths
For example, this workflow will trigger on a push when any files under the path service_A/ have changed (note the ** glob to match files in nested directories).
on:
push:
paths:
- 'service_A/**'

Answer 2

You could also run some script to discover which services were changed based on git diff and trigger corresponding job via GitHub REST API.
There could be two workflows main.yml and services.yml.
Main workflow will be configured to be started always on push and it will only start script to find out which services were changed. For each changed service repository dispatch event will be triggered with service name in payload.
Services workflow will be configured to be started on repository_dispatch and it will contain one job for each service. Jobs would have additional condition based on event payload.
See showcase with similar setup:
https://github.com/zladovan/monorepo

Answer 3

It's not a Monorepo
If you only have apps, then I'm sorry... but all you have is a repo of many apps.
A monorepo is a collection of packages that you can map a graph of dependencies between.
Aha, I have a monorepo
But if you have a collection of packges which depend on each other, then read on.
apps/
one/
depends:
pkg/foo
two/
depends:
pkg/bar
pkg/foo
pkg/
foo/
bar/
baz/
The answer is that you switch to a tool that can describe which packages have changed between the current git ref and some other git ref.
The following two examples runs the release npm script on each package that changed under apps/* and all the packges they would depend on.
I'm unsure if the pnpm method silently skips packages that don't have a release target/command/script.
Use NX Dev
Using NX.dev, it will work it out for you with its nx affected command.
you need a nx.json in the root of your monorepo
it assumes you're using the package.json approach with nx.dev, if you have project.json in each package, then the target would reside there.
your CI would then look like:
pnpx nx affected --target=release
Pnpm Filtering
Your other option is to switch to pnpm and use its filtering syntax:
pnpm --filter "...{apps/**}[origin/master]" release
Naive Path Filtering
If you just try and rely on "which paths" changed in this git commit, then you miss out on transient changes that affect the packages you actually want to deploy.
If you have a github action like:
on:
push:
paths:
- 'app/**'
Then you won't ever get any builds for when you only push commits that change anything in pkg/**.
Other interesting github actions
https://github.com/marketplace/actions/nx-check-changes
https://github.com/marketplace/actions/nx-affected-dependencies-action
https://github.com/marketplace/actions/nx-affected-list (a non nx alternative here is dorny/paths-filter
https://github.com/marketplace/actions/nx-affected-matrix

Answer 4

Has Changed Path Action might be worth a try:
name: Conditional Deploy
on: push
jobs:
build:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout#v2
with:
fetch-depth: 100
- uses: marceloprado/has-changed-path#v1
id: service_A_deployment
with:
paths: service_A
- name: Deploy front
if: steps.service_A_deployment.outputs.changed == 'true'
run: /deploy-service_A.sh