Introduction to GitHub Actions - How to easily automate and integrate with GitHub

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© 2021 Brent C. Laster &
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Tech Skills Transformations & Brent Laster
Introduction to GitHub Actions

@techupskills
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About me
• R&D Director, DevOps
• Global trainer – training (Git,
Jenkins, Gradle, CI/CD,
pipelines, Kubernetes,
Helm, ArgoCD, operators)
• Author -
§ OpenSource.com
§ Professional Git book
§ Jenkins 2 – Up and
Running book
§ Continuous Integration
vs. Continuous Delivery
vs. Continuous
Deployment mini-book
on Safari
techskillstransformations.com
getskillsnow.com
https://www.linkedin.com/in/brentlaster
@BrentCLaster
GitHub: brentlaster

@techupskills
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Book – Professional Git
• Extensive Git reference,
explanations, and examples
• First part for non-technical
• Beginner and advanced
reference
• Hands-on labs

@techupskills
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Jenkins 2 Book
• Jenkins 2 – Up and Running
• “It’s an ideal book for those who are
new to CI/CD, as well as those who
have been using Jenkins for many
years. This book will help you discover
and rediscover Jenkins.” By Kohsuke
Kawaguchi, Creator of Jenkins

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O’Reilly Training

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What are GitHub Actions?
• Way to create custom, automated workflows in GitHub
• Executed based on repository operations
• Building blocks - can be combined & shared
• Used for usual SDLC tasks
• Can be used for CI/CD as alternatives to other apps

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What's interesting about it?
• Direct integration with GitHub

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What else is interesting about it?
• Lots of events can trigger an action workflow -
automate practically anything!
on: project
on: watch
on: repository_dispatch
on: delete
on: check_run
on: page_build
on: scheduled
on: pull_request
on: public
on: pull_request_review_comment
on: pull_push
on: fork
https://docs.github.com/en/actions/learn-github-actions/events-that-trigger-workflows

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Types of triggers for events
• single event - on: push
• list of events - on: [push, pull_request]
• specify activity types or configuration - on:
push:
branches:
- main
• scheduled events - on:
scheduled:
- cron: '30 5,15 * * *'
• manual events - on: workflow-dispatch
on: repository-dispatch
[opened, deleted]
• workflow reuse events - on: workflow-call
(can be called from another workflow)
• webhook events - on: issue_comment
on: pull_request

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How actions work? (events)
• Events occur
§ Example: pull request
triggers build for
validation
§ Example: push for
commit
• Repository Dispatch
Events
§ Endpoint that can be
used to trigger webhook
event
§ Can be used for activity
that is not in GitHub
§ Can trigger a GitHub
Actions workflow or
GitHub App webhook
• ref
https://docs.github.com
/en/rest/reference/repo
s#create-a-repository-
dispatch-event
Event

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How actions work (workflows)
• Events trigger workflows
workflow
Event
§ Procedure to run
automatically
§ Added to your repository
§ Composed of one+ jobs
§ Can be triggered/scheduled
by event
§ Useful for doing CI/CD
actions such as building,
testing, packaging, etc.

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How actions work (jobs, steps, actions)
Workflows contain jobs
§ Set of steps
§ Workflow with multiple jobs runs them in parallel
Jobs contain steps
§ A task that can execute commands in a job
§ Can be either
» action
» shell command
workflow
Job 1
Job 2
Event
Step 1
Step 1
Step 2
Action
Action
Action
Action
§ Independent
commands
§ Combined into
steps to form a job
§ Smallest unit in a
workflow
§ Can be created or
pulled in from the
community
§ Only usable if
included as a step

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How actions work (runner)
Runner
• A server with GitHub
Actions runner app
on it
• Can use runner
provided by/hosted
via GitHub or use
your own
• Runner listens for
available jobs
• Steps in a job execute
on the same runner
workflow
Job 1
Job 2
Event
Step 1
Step 1
Step 2
Action
Action
Action
Runner 1
Action Runs
Log results
Runner 2
Action Runs
Log results

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How workflows are triggered
1. Event happens in repo
2. Resulting event has SHA and Git ref (branch)
3. .github/workflows dir in repo is searched for
workflow files in same SHA or ref
4. workflow files for commit and ref are inspected
5. new workflow run triggered for any workflow with
matching "on:" values

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How actions work
GitHub Repository
.github
workflows
workflow1.yml
Job 1
Step 1
Action
Step 2
Action
Job 2
Step 1
Action
workflow2.yml
Job 1
Step 1
Action
Job 2
Step 1
Action
Step 2
Action
Runner 1
Action Runs
Log results
Runner 2
Action Runs
Log results
Event
• Resides in
.github/workflows
• Can have multiple
workflows

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Editing Actions

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Updating workflows with Pull Requests #1

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Searching for a Public Action

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Custom Actions
• Can be created by you
• Can result from customizing community actions
• Can be put on Marketplace and shared
• repository must be public
• Can integrate with any public API
• Can run directly on a machine or in Docker
container
• Can define inputs, outputs, and environment
variables
• Require metadata file
• defines inputs, outputs, and entrypoint
• must be named either action.yaml or
action.yml
• Should be tagged with a label and then pushed to
GitHub
• To use:
• In file in .github/workflows/main.yml
• In steps
• "uses: <github path to action>@<label>
$ <create GitHub repo>
$ <clone repo>
$ <create files>
$ git add action.yml <other files>
$ git commit -m "action files"
$ git tag -a -m "first release of action" v1
$ git push --follow-tags
on: [push]
jobs:
example_job:
runs on: ubuntu-latest
name: An example job
steps:
- name: Example step
id: example_step
uses: <repo name>/<action name>@<tag>
...
.github/workflows/example.yml

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Custom Action Types
• Docker
• Packages env with actions code
• Env can include specific OS versions,
config, tools, etc.
• Well suited for specific env needs
• Runs only on Linux runners with
Docker installed
• Slower due to cost of building and
retrieving container
• GitHub builds image from Dockerfile
and runs comands in a new
container based on image
• Javascript
• Run directly on runner for any of
macOS, Linux, or Windows
• Separates action from env
• Fast than Docker
• Needs to be pure JavaScript (no
other binaries)
• Can use binaries already on runner
• Composite
• Combines multiple workflow steps
in one action
Runner
FROM <base> ....
COPY <entry script>
ENTRYPOINT <script>
Dockerfile
...
runs:
using: 'docker'
image: 'Dockerfile'
args:
....
action.yml
+ +
Runner
+ +
...
runs:
using: 'node12'
main: 'index.js'
action.yml
npm install @actions/core
npm install @actions/github
const core =
require('@actions/core');
const github =
require('@actions/github);
try{
...
} catch (error) {
...
}
index.js
Runner
...
runs:
using: 'composite'
- run: echo ...
- run: ${{ github.action.path
}}/shell-script.sh
action.yml
+
echo ...
...
shell-script.sh

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Actions Toolkit
• Provides packages for more
easily creating/working with
actions
• Functions in packages can be
run in code as in
core.setOutput('SELECTED_COLOR
', 'red');
or (in many cases)
• run as workflow commands
- name: Set selected color run:
echo '::set-output
name=SELECTED_COLOR::green'

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Actions Toolkit packages
• Collections of
related
functions
• Can be
imported into
code for actions

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Environment Variables for Actions
• GitHub sets a set of default
env vars for each run of an
action
• Can set custom variables in
workflow file
• Case-sensitive
• Can be for step, job, or
overall workflow
jobs:
my_job:
env:
LEVEL: admin
steps:
- auth: "Check if admin"
if: {{ env.LEVEL == 'admin' }}
run: echo "Detected admin user
$USER_ID."
env:
USER_ID: abc123
• if in "run" key - reads env var from
runner OS after job sent to runner
• else use env "context" because
variable must be sub'd during
processing of workflow - before sent
to runner
Default Environment Variables
GITHUB_WORKFLOW GITHUB_RUN_ID
GITHUB_RUN_NUMBER GITHUB_JOB
GITHUB_ACTION GITHUB_ACTION_PATH
GITHUB_ACTIONS GITHUB_ACTOR
GITHUB_REPOSITORY GITHUB_EVENT_NAME
GITHUB_EVENT_PATH GITHUB_WORKSPACE
GITHUB_SHA GITHUB_REF
GITHUB_HEAD_REF GITHUB_BASE_REF
GITHUB_SERVER_URL GITHUB_API_URL
GITHUB_GRAPHQL_URL RUNNER_NAME
RUNNER_OS RUNNER_TEMP
RUNNER_TOOL_CACHE CI
Ref: https://docs.github.com/en/actions/learn-github-
actions/environment-variables

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Viewing the Workflow Run history

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Viewing a Specific Workflow Run

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Drilling into logs
• Click on workflow in list
• Click on step
• Step log is shown
• Gear icon can be used for
options - such as timestamps
• Can also view raw logs

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GitHub Actions Runner

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GitHub Actions Virtual Environments
• Virtual
environments
for GitHub
actions hosted
runners
• VM images of
Microsoft-
hosted agents
used for Azure
Pipelines

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GitHub-hosted vs Self-hosted Runners
GitHub-hosted Self-hosted
Definition Hosted by GitHub Any system/configuration
you want to use
Prereqs Running GitHub actions
runner application
GitHub actions self-hosted
runner application
Platforms Windows, Linux, MacOS Any that can be made to
work
Advantages Quicker and simpler Highly configurable
Management/Ownership GitHub As defined
Clean instance For every job execution Optional
Cost Free minutes on GitHub
plan with cost for overages
Free to use with actions,
but owner is responsible
for any other cost
Automatic updates For OS, installed packages,
tools, and hosted runner
application
Only for self-hosted runner
application
Implementation Virtual Virtual or physical

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GitHub Actions Storage - Artifacts
• Actions allow you to persist data after job has completed - as artifacts
• Artifact - file or collection of files produced during workflow run
§ build and test output
§ log files
§ binary files
• Artifacts are uploaded during workflow run
§ can be shared between jobs in same workflow
§ visible in the UI
• Default retention period is 90 days

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What are the limits?
• Job execution time - each job can run up to 6 hours of execution time
§ At 6 hours, job is terminated and fails to complete
• Workflow run time - each workflow run limited to 72 hours
§ At limit, workflow run is cancelled
• API requests - can execute up to 1000 API requests in an hour across all actions in a
single repo
§ Past limit, additional API calls will fail
• Concurrent jobs - number of concurrent jobs depends on plan
§ Past limit, additional jobs are queued
GitHub plan Total concurrent jobs Maximum concurrent
macOS jobs
Free 20 5
Pro 40 5
Team 60 5
Enterprise 180 50

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How much does it cost? (part 1)
• Free for both public repos and self-hosted runners
• For private repos, each GitHub account gets
designated amount of free minutes and storage
§ above that, usage is controlled by spending limits
§ minutes reset every month, but not storage
Product Storage Minutes (per month)
GitHub Free 500 MB 2,000
GitHub Pro 1 GB 3,000
GitHub Free for
organizations
500 MB 2,000
GitHub Team 2 GB 3,000
GitHub Enterprise
Cloud
50 GB 50,000

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How much does it cost? (part 2)
• Total storage is Actions artifacts and GitHub Packages
§ GitHub Packages = platform for hosting and managing packages, such as containers or
dependencies
• Storage usage is calculated for each month based on hourly usage during the month
• Per-minute rates
• If jobs run on Windows or macOS on runners hosted by GitHub, multiplier comes into play
Operating system Minute multiplier
Linux 1
macOS 10
Windows 2
Operating system Per-minute rate
(USD)
Linux $0.008
macOS $0.08
Windows $0.016

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Upcoming Training on GitHub Actions

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That’s all - thanks!
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Introduction to GitHub Actions - How to easily automate and integrate with GitHub

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