jonelantha: Blog

Refactoring your GitHub Actions workflow into a script

Is your GitHub Actions workflow file getting a bit large and perhaps a little difficult to follow? Or maybe you want to share logic between multiple workflows in the same repo and want to keep things ‘DRY’? In this article we’ll compare using different scripting engines to extract out code from a workflow.

The problem

Here’s a workflow which deploys files to an Amazon S3 bucket and then invalidates a Cloudfront Distribution using the AWS CLI. This is a common situation for anyone deploying a static website site to AWS.

name: Deployment Workflow


jobs:
  deploy:
    runs-on: ubuntu-latest
    steps:
    ...
    - name: Deploy
      run: |
        aws s3 sync ./public/ s3://my-test-bucket --delete
        aws cloudfront create-invalidation  --distribution-id MYCLOUDFRONTID --paths /*

This example has only two commands and those two commands don’t have too many command line options. However, real world solutions will often be more complex.

The best practice is to create your own GitHub Action (see the official GitHub guide for more details). There’s quite a lot of overhead with this approach and if you’re only working on a single repo it’s probably easiest just to move the logic into a script within the same repo.

So how should our script work?

Ideally the script should tick the following boxes:

1. A Bash script

deploy.sh

#!/bin/bash


# Read named command line arguments into an args variable


declare -A args


while (( "$#" )); do
    if  [[ $1 == --* ]] && [ "$2" ]; then
        args[${1:2}]=$2
        shift
    fi
    shift
done


# Do the deployment


aws s3 sync ./build/ "s3://${args[bucketname]}" --delete


if [ -n "${args[cloudfrontid]}" ]; then
    aws cloudfront create-invalidation  --distribution-id "${args[cloudfrontid]}" --paths /*
fi

And inside the workflow yml file:

...
    steps:
    ...
    - name: Deploy
      run: ./scripts/deploy.sh --bucketname my-test-bucket --cloudfrontid MYCLOUDFRONTID

Pros:

Cons:

2. A Python script

deploy.py

import argparse
import os


parser = argparse.ArgumentParser(description='Deploy')
parser.add_argument('--bucketname', dest='bucketname', required=True)
parser.add_argument('--cloudfrontid', dest='cloudfrontid')


args = parser.parse_args()


os.system(f'aws s3 sync ./build/ s3://{args.bucketname} --delete')


if args.cloudfrontid:
    os.system(f'aws cloudfront create-invalidation  --distribution-id {args.cloudfrontid} --paths /*')

And inside the workflow yml file:

...
    - name: Deploy
      run: python3 ./scripts/deploy.sh --bucketname my-test-bucket --cloudfrontid MYCLOUDFRONTID

Pros:

Cons:

3. A PowerShell script

deploy.ps1

Terminal window
param (
    [Parameter(Mandatory)]
    [string]$BucketName,
    [string]$CloudfrontID
)


iex "aws s3 sync ./build/ s3://$BucketName --delete"


if ($CloudfrontID) {
    iex "aws cloudfront create-invalidation  --distribution-id $CloudfrontID --paths /*"
}

And the entry in the workflow yml file:

...
    - name: Deploy
      run: pwsh ./scripts/deploy.ps1 -BucketName my-test-bucket -CloudfrontID MYCLOUDFRONTID

Pros:

Cons:

4. A Node script

deploy.js

const { execSync } = require('child_process');
const yargs = require('yargs');


const args = yargs.options({
  'bucketname': { demandOption: true },
  'cloudfrontid': {},
}).argv;


execSync(
  `aws s3 sync ./build/ s3://${args.bucketname} --delete`,
  {stdio: 'inherit'}
);


if (args.cloudfrontid) {
  execSync(
    `aws cloudfront create-invalidation  --distribution-id ${args.cloudfrontid} --paths /*`,
    {stdio: 'inherit'}
  );
}

And the workflow yml file:

...
    - name: Deploy
      run: node ./scripts/deploy.js --bucketname my-test-bucket --cloudfrontid MYCLOUDFRONTID

Pros:

Cons:

5. A Node based GitHub Action in the same repo

For a step by step guide to using this method see the article ‘Create your own local js GitHub Action with just two files’

deploy.js

const core = require("@actions/core");
const { exec } = require("@actions/exec");


async function deploy() {
  const bucketName = core.getInput('bucket-name');
  await exec(`aws s3 sync ./build/ s3://${bucketName} --delete`);


  const cloudfrontID = core.getInput('cloudfront-id');
  if (cloudfrontID) {
    await exec(`aws cloudfront create-invalidation  --distribution-id ${cloudfrontID} --paths /*`);
  }
}


deploy()
  .catch(error => core.setFailed(error.message));

action.yml

name: "Deploy"
description: "Deploy action"
inputs:
  bucket-name:
    description: "S3 Bucket"
    required: true
  cloudfront-id:
    description: "Cloudfront ID"
runs:
  using: "node12"
  main: "deploy.js"

And the workflow yml file:

...
    - name: Deploy
      uses: ./actions/deploy
        with:
          bucket-name: my-test-bucket
          cloudfront-id: MYCLOUDFRONTID

Pros:

Cons:

TL;DR