Unlocking the Power of GitHub Event Data with Actions and Pages

As a full-stack developer, I‘m always looking for ways to automate workflows and extract valuable insights from the vast amount of data generated by the software development process. With the rise of GitHub Actions and Pages, we now have a powerful set of tools for capturing, analyzing and publishing GitHub event data.

In this in-depth guide, I‘ll show you how to harness the potential of GitHub events to build data-driven experiences and automations around your repositories. We‘ll dive deep into the technical details of accessing event payloads, persisting data, and publishing to static sites. Along the way, I‘ll share expert tips, real-world examples, and insights drawn from years of experience as a full-stack developer.

Whether you‘re looking to create a project status dashboard, an automatically updating blog, or an interactive release notes site, this guide will equip you with the knowledge and skills to unlock the hidden potential of your repository data. Let‘s get started!

The Scale and Significance of GitHub Event Data

To put the opportunity in context, let‘s look at some key statistics:

• GitHub has over 40 million users and 100 million repositories (as of January 2020)
• Over 80% of Fortune 100 companies use GitHub Enterprise
• There were 44 million new repositories created in 2019 alone
• The GitHub API serves over 60 billion requests per year

Event Type	Events Per Month
Push	291,684,541
PullRequest	24,186,442
Issues	12,364,652
Create	11,625,001
Delete	8,921,690
Gollum	2,457,910
IssueComment	8,069,812
Fork	5,978,487

Table 1: GitHub event statistics for January 2020 (Source: GitHub Archive)

As these numbers show, GitHub repositories generate a massive amount of event data across a wide range of categories. Each event represents an opportunity to gain insights, automate processes, and enhance the development experience.

Traditionally, accessing and working with this data required using the GitHub API and building custom integrations. However, with the launch of GitHub Actions in 2019, it‘s become much easier to programmatically interact with repositories and their event data directly from the platform.

Accessing Event Payloads in GitHub Actions

GitHub Actions is an automation platform deeply integrated with the rest of GitHub‘s featureset. It allows defining custom workflows triggered by repository events. When an event like a new commit or issue comment occurs, the corresponding workflow is executed in an isolated virtual machine.

Each workflow run has access to the full event payload that triggered it via special environment variables and a JSON file on disk. The payload contains all the relevant data about the event, such as the repository, sender, and any associated commits, issues, or pull requests.

To access the event payload, we can use the GITHUB_EVENT_PATH environment variable, which points to a file containing the full JSON data. For example, to read the payload for an IssuesEvent triggered by opening a new issue:

issue_payload=$(cat $GITHUB_EVENT_PATH)
issue_title=$(echo $issue_payload | jq -r ‘.issue.title‘)
issue_number=$(echo $issue_payload | jq -r ‘.issue.number‘)

Here we‘re using cat to read the contents of the JSON file, then parsing out specific fields with the jq tool. The -r flag tells jq to return the result as a plain string.

For convenience, the most commonly accessed event data is also available in the github.event context, which can be referenced directly in the workflow yaml:

on:
  issues:
    types: [opened]

jobs:
  process_issue:
    runs-on: ubuntu-latest
    steps:
      - env:
          ISSUE_TITLE: ${{ github.event.issue.title }}
          ISSUE_NUMBER: ${{ github.event.issue.number }}
        run: |
          echo "New issue opened: $ISSUE_TITLE (#$ISSUE_NUMBER)"

This more concise syntax is great for simpler workflows, but using jq to parse the full payload provides the most flexibility and control.

With access to the raw event data, the next step is to extract any relevant information and persist it beyond the lifecycle of the workflow run.

Strategies for Persisting Event Data

Event data is only accessible during the workflow run triggered by the event. Once the workflow finishes, the virtual machine is terminated and all data is lost. To make use of the data in later workflow runs or publish it to a repository, we need to persist it.

There are two main approaches: artifacts and repository files.

Persisting Data as Artifacts

Artifacts allow sharing data between jobs in a workflow run. This is useful when we need to perform some pre-processing or aggregation on the event data before using it in a later job.

To create an artifact, use the actions/upload-artifact action:

- uses: actions/upload-artifact@v2
  with:
    name: event-data
    path: ${{ github.event_path }}

This will take the JSON event payload and upload it as an artifact named event-data, making it available to subsequent jobs.

To access the artifact in another job, use the actions/download-artifact action:

- uses: actions/download-artifact@v2
  with:
    name: event-data

This will download the event-data artifact and place it in the job‘s workspace directory, where it can be read and processed by other steps.

Artifacts are a good fit for temporary data that doesn‘t need to be committed to the repository. However, they only persist for the duration of the workflow run – typically up to 90 days. For data that needs to be stored long-term or published, we need to commit it to the repository.

Persisting Data in Repository Files

Committing event data to repository files provides the most flexibility and control. The data becomes part of the repository history, and can be used to build documentation sites, reports, or other artifacts.

To commit to a repository from an Actions workflow, we first need to check out the repository using the actions/checkout action:

- uses: actions/checkout@v2

Then, we can write the event data to a file using standard shell commands. For example, to append the data to a JSON Lines file:

echo $EVENT_DATA >> data.jsonl

We can also transform the data before writing it to a file. For example, to create an HTML fragment from an issue comment event:

COMMENT_BODY=$(echo ${{ github.event.comment.body }} | sed ‘s/"/\\"/g‘)

cat >> comment.html <<EOL
<div class="comment">
  <p class="comment-author">${{ github.event.comment.user.login }}</p>  
  <p class="comment-body">$COMMENT_BODY</p>
</div>
EOL

This uses sed to escape any double quotes in the comment body, then outputs an HTML snippet to comment.html using a heredoc.

After creating or updating the desired files, we need to commit and push the changes back to the repository:

- name: Commit changes
  run: |
    git config user.email "[email protected]"  
    git config user.name "GitHub Actions"
    git add data.jsonl comment.html
    git commit -m "Add event data"
    git push

This sets up the git user, stages the new and updated files, creates a commit, and pushes it to the default branch. By default, the GITHUB_TOKEN secret is used to authenticate the push.

With the event data committed to the repository, we can now use it to build documentation sites, dashboards, or any other desired output.

Publishing Event Data to GitHub Pages

GitHub Pages is a web hosting service that lets you publish static sites directly from a repository. It‘s an ideal platform for showcasing data generated from repository events.

To publish to Pages, we first need to generate the site files (HTML, CSS, etc.) and commit them to the repository. We can do this using a static site generator like Jekyll or Hugo, or by writing the files directly in the workflow.

For example, to generate an HTML page displaying recent issue comments:

- name: Generate comment page
  run: |
    cat > index.html <<EOL
    <html>
      <head>
        <title>Recent Comments</title>
      </head>
      <body>

        <ul>
          $(ls -t *.html | head -n 10 | sed ‘s/^/<li><a href="&">/;s/$/<\/a><\/li>/‘)
        </ul>
      </body>
    </html>
    EOL

This generates an index.html file with a list of links to the 10 most recent comment files (generated in the previous step). The ls and sed commands are used to build the list items.

Once the site files are committed to the repository, we can publish to Pages by configuring the repository settings. Under the "Pages" section, choose the branch to publish from (e.g. main or gh-pages) and the directory containing the site files (usually / or /docs).

By default, the GITHUB_TOKEN secret used to authenticate the workflow doesn‘t have permission to deploy to Pages. To enable deployments, we need to create a personal access token (PAT) with the repo scope and add it to the repository secrets.

Then, update the workflow to use the PAT for the push step:

- name: Deploy to Pages
  env:
    GITHUB_TOKEN: ${{ secrets.PAGES_DEPLOY_TOKEN }}
  run: |  
    git push origin main  

Replace PAGES_DEPLOY_TOKEN with the name of your PAT secret. With this configuration, the workflow will trigger a Pages build whenever it pushes to the specified branch.

After the build completes (usually within a few minutes), the updated site will be live at https://<username>.github.io/<repository>/.

Real-World Examples and Use Cases

Now that we‘ve covered the key technical concepts, let‘s explore some real-world examples of using GitHub Actions and Pages to publish event data.

Project Status Dashboard

Imagine you want to create a dashboard showing the current status of your project – things like open issues, pull request activity, and contributor stats. With Actions, you can generate this dashboard automatically using repository event data.

Here‘s a high-level outline of the workflow:

1. Trigger on a schedule (e.g. daily) or relevant events (e.g. issues, pull_request)
2. Query the GitHub API to fetch additional data (e.g. total issues, PRs, contributors)
3. Process the data and generate an HTML dashboard
4. Commit the dashboard to the gh-pages branch
5. Configure Pages to publish from the gh-pages branch

This approach allows you to create a fully automated dashboard that stays up-to-date with the latest project activity. By leveraging Actions and Pages, there‘s no need to manually update the dashboard or host it externally.

Changelog Generator

Another common use case is generating a changelog from repository events. By parsing events like pull requests and releases, you can create a nicely formatted changelog without the manual effort.

Here‘s how it might work:

1. Trigger on release events
2. Fetch all merged pull requests since the last release
3. Extract the relevant details (title, description, author) from each PR
4. Generate a markdown changelog from the PR data
5. Commit the changelog to the repository
6. Optionally, publish the changelog to Pages for easy access

This workflow automates the tedious process of manually compiling a changelog, ensuring it‘s always accurate and up-to-date.

Interactive Q&A Site

You can also use GitHub events to power an interactive Q&A site, similar to Stack Overflow. Users can ask questions by opening issues, and answers can be posted as comments.

The workflow might look like this:

1. Trigger on issue and issue_comment events
2. For new issues, create a corresponding HTML page with the question details
3. For new comments, update the relevant question page with the answer
4. Commit the updated pages to the repository
5. Publish the Q&A site to Pages

By leveraging GitHub‘s built-in issue tracking and Pages hosting, you can create a fully functional Q&A site without any external dependencies.

These are just a few examples of the kinds of data-driven applications you can build with GitHub Actions and Pages. The possibilities are endless!

The Future of GitHub Automation

As GitHub continues to evolve its automation offerings, I believe we‘ll see even more powerful ways to leverage repository data.

One area I‘m particularly excited about is the potential for more granular event triggers and filters. Imagine being able to trigger a workflow only for certain types of issues (e.g. bugs), or when a pull request is merged to a specific branch.

I also anticipate tighter integration between Actions and other GitHub features like Projects and Packages. This could enable workflows that automatically update project boards based on issue activity, or publish new package versions when a release is created.

As the GitHub ecosystem grows, I expect to see a flourishing of third-party Actions and integrations that make it even easier to build sophisticated automations. We‘re already seeing examples of this with tools like Publish to GitHub Pages, which streamlines the process of deploying a static site.

Ultimately, I believe GitHub is well-positioned to become the central hub for all aspects of the software development lifecycle – from planning and coding to deployment and monitoring. By providing a unified platform for automation and data access, GitHub is empowering developers to create more efficient, collaborative, and data-driven workflows.

Conclusion

In this guide, we‘ve explored the exciting possibilities of leveraging GitHub event data with Actions and Pages. By capturing and publishing this data, we can create dynamic, data-driven applications and automations that enhance the development experience.

We‘ve covered the key concepts and techniques, including:

• Accessing event payloads in Actions workflows
• Persisting data as artifacts and repository files
• Publishing data to GitHub Pages
• Real-world examples and use cases
• Future directions for GitHub automation

As a full-stack developer, I‘m thrilled by the potential of these tools to streamline and enrich my workflows. I encourage you to experiment with them in your own projects, and see what kinds of creative solutions you can build.

Remember, the key is to start small and iterate. Begin by capturing a single event type and publishing it to a simple Pages site. Then gradually add more data sources and features as you become comfortable with the process.

If you have any questions or feedback, feel free to reach out. I‘m always eager to learn from others in the community.

Happy automating!