> ## Documentation Index > Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt > Use this file to discover all available pages before exploring further. # Create a Docker Action > Learn to create a Docker-based GitHub Action that posts a random Giphy Thank You GIF on pull request events. In this tutorial, learn how to develop a custom Docker-based GitHub Action that automatically posts a random “Thank You” GIF from Giphy whenever someone opens a pull request. This CI/CD integration covers: * Triggering on `pull_request` events * Fetching a random GIF via the Giphy REST API * Commenting on the pull request with the GitHub REST API We’ll securely store API keys in GitHub Secrets and encapsulate the entire implementation in a Docker container. ## Table of Contents 1. [Giphy REST API](#1-giphy-rest-api) 2. [GitHub REST API for Comments](#2-github-rest-api-for-comments) 3. [Creating the Repository](#3-creating-the-repository) 4. [Configuring GitHub Secrets](#4-configuring-github-secrets) 5. [Project Structure Overview](#5-project-structure-overview) 6. [Dockerfile Configuration](#6-dockerfile-configuration) 7. [Entrypoint Script](#7-entrypoint-script) 8. [Action Metadata (`action.yml`)](#8-action-metadata-actionyml) 9. [Test Workflow Setup](#9-test-workflow-setup) 10. [Opening a Pull Request](#10-opening-a-pull-request) 11. [Verifying the Workflow](#11-verifying-the-workflow) 12. [Reviewing the Bot Comment](#12-reviewing-the-bot-comment) 13. [Links and References](#13-links-and-references) *** ## 1. Giphy REST API Use the Giphy **[Random GIF endpoint](https://developers.giphy.com/docs/api/endpoint#random)** to retrieve a random “thank you” GIF. Store your GIPHY API key in GitHub Secrets and reference it in the action: ```http theme={null} GET https://api.giphy.com/v1/gifs/random?api_key=&tag=thank%20you&rating=g ``` A sample JSON response: ```json theme={null} { "data": { "images": { "original": { "url": "https://media1.giphy.com/media/l119IDMNbVsKgyf5u/giphy.gif" }, "downsized": { "url": "https://media1.giphy.com/media/l119IDMNbVsKgyf5u/200w_d.gif" } } } } ``` Extract the GIF URL from `.data.images.downsized.url` using [`jq`](https://stedolan.github.io/jq/). *** ## 2. GitHub REST API for Comments To comment on a PR, call GitHub’s **[Create an issue comment](https://docs.github.com/rest/issues/comments#create-an-issue-comment)** endpoint. Issues and pull request comments use the same API. ![The image shows a GitHub documentation page for the REST API, specifically focusing on managing issues, with links to various related actions like listing, creating, and updating issues.](https://kodekloud.com/kk-media/image/upload/v1752876036/notes-assets/images/GitHub-Actions-Certification-Create-a-Docker-Action/github-rest-api-managing-issues.jpg) | HTTP Method | Endpoint | Purpose | | ----------- | ---------------------------------------------------------------------------- | ------------------- | | POST | `https://api.github.com/repos/{owner}/{repo}/issues/{issue_number}/comments` | Create a PR comment | Example `curl` command: ```bash theme={null} curl -s -X POST \ -H "Accept: application/vnd.github+json" \ -H "Authorization: Bearer " \ https://api.github.com/repos/OWNER/REPO/issues/ISSUE_NUMBER/comments \ -d '{"body":"Thank you for this contribution! 🎉"}' ``` *** ## 3. Creating the Repository Initialize a new public repository named `docker-action-pr-giphy-comment` with a `README.md`: ![The image shows a GitHub page for creating a new repository, with fields for the repository name, description, and options for public or private settings.](https://kodekloud.com/kk-media/image/upload/v1752876037/notes-assets/images/GitHub-Actions-Certification-Create-a-Docker-Action/github-new-repository-creation-page.jpg) After creation, you’ll see the initial commit: ![The image shows a GitHub repository page titled "docker-action-pr-giphy-comment" with an initial commit and a README file. The repository has no stars, forks, or releases.](https://kodekloud.com/kk-media/image/upload/v1752876039/notes-assets/images/GitHub-Actions-Certification-Create-a-Docker-Action/github-repo-docker-action-readme.jpg) *** ## 4. Configuring GitHub Secrets Store sensitive information under **Settings > Secrets and variables > Actions**: ![The image shows a GitHub repository settings page where a new secret is being added under "Actions secrets." The secret is named "GIPHY\_API\_KEY."](https://kodekloud.com/kk-media/image/upload/v1752876040/notes-assets/images/GitHub-Actions-Certification-Create-a-Docker-Action/github-repo-settings-add-secret-giphy-api-key.jpg) You will add: * `GIPHY_API_KEY` for the Giphy API * Use the built-in `GITHUB_TOKEN` for commenting on PRs *** ## 5. Project Structure Overview Your repository should contain the following files: ![The image shows a code editor with a project directory open, displaying files like action.yml, Dockerfile, and entrypoint.sh in a GitHub repository. The README.md file is open in the editor pane.](https://kodekloud.com/kk-media/image/upload/v1752876041/notes-assets/images/GitHub-Actions-Certification-Create-a-Docker-Action/code-editor-github-repo-files.jpg) | File | Purpose | | ---------------------------- | ---------------------------------- | | `Dockerfile` | Defines the container environment | | `entrypoint.sh` | Handles the action logic | | `action.yml` | Action metadata and inputs | | `.github/workflows/test.yml` | Workflow to test the action on PRs | *** ## 6. Dockerfile Configuration Create a lightweight container with required utilities: ```dockerfile theme={null} FROM alpine:3.10 # Install HTTP client and JSON parser RUN apk update && apk add --no-cache curl jq # Copy and set entrypoint script permissions COPY entrypoint.sh /entrypoint.sh RUN chmod +x /entrypoint.sh ENTRYPOINT ["/entrypoint.sh"] ``` *** ## 7. Entrypoint Script The `entrypoint.sh` script orchestrates: 1. Reading the PR number from the GitHub event payload 2. Fetching a random “thank you” GIF 3. Parsing the GIF URL 4. Posting a comment on the PR ```bash theme={null} #!/bin/sh GITHUB_TOKEN=$1 GIPHY_API_KEY=$2 # Get PR number pr_number=$(jq --raw-output .pull_request.number "$GITHUB_EVENT_PATH") echo "PR Number: $pr_number" # Fetch GIF from Giphy giphy_response=$(curl -s \ "https://api.giphy.com/v1/gifs/random?api_key=$GIPHY_API_KEY&tag=thank%20you&rating=g") echo "Giphy Response: $giphy_response" # Extract GIF URL gif_url=$(echo "$giphy_response" | jq --raw-output .data.images.downsized.url) echo "GIF URL: $gif_url" # Post comment response=$(curl -s -X POST \ -H "Authorization: token $GITHUB_TOKEN" \ -H "Accept: application/vnd.github.v3+json" \ -d "{\"body\": \"Thank you for your contribution! 🎉\n![GIF]($gif_url)\"}" \ "https://api.github.com/repos/$GITHUB_REPOSITORY/issues/$pr_number/comments") echo "Comment posted: $(echo "$response" | jq --raw-output .html_url)" ``` *** ## 8. Action Metadata (`action.yml`) Define inputs and Docker run settings: ```yaml theme={null} name: 'Giphy PR Comment' description: 'Automatically add a thank-you Giphy GIF to pull requests.' inputs: github-token: description: 'Token for GitHub API authentication' required: true giphy-api-key: description: 'Secret key for Giphy API' required: true runs: using: 'docker' image: 'Dockerfile' args: - ${{ inputs.github-token }} - ${{ inputs.giphy-api-key }} ``` *** ## 9. Test Workflow Setup Configure `.github/workflows/test.yml` to trigger on PR opens: ```yaml theme={null} on: pull_request: types: [opened] jobs: test-giphy-action: runs-on: ubuntu-latest permissions: issues: write pull-requests: write steps: - name: Checkout code uses: actions/checkout@v3 - name: Invoke Giphy PR Comment Action uses: ./ with: github-token: ${{ secrets.GITHUB_TOKEN }} giphy-api-key: ${{ secrets.GIPHY_API_KEY }} ``` *** ## 10. Opening a Pull Request Make a small update (e.g., edit `README.md`) in a feature branch to trigger the workflow: ![The image shows a GitHub repository interface where a user is editing the README.md file in a project named "docker-action-pr-giphy-comment."](https://kodekloud.com/kk-media/image/upload/v1752876042/notes-assets/images/GitHub-Actions-Certification-Create-a-Docker-Action/github-repo-edit-readme-docker-action.jpg) Create and submit the PR: ![The image shows a GitHub pull request page for updating a README.md file. It indicates that some checks are pending, and the branch has no conflicts with the base branch.](https://kodekloud.com/kk-media/image/upload/v1752876043/notes-assets/images/GitHub-Actions-Certification-Create-a-Docker-Action/github-pull-request-readme-update.jpg) *** ## 11. Verifying the Workflow Monitor the Action run under **Actions**. A successful run indicates: ![The image shows a GitHub Actions interface with a successful workflow run named "testing-action," detailing steps like setting up a job, checking out a repository, and posting a PR comment.](https://kodekloud.com/kk-media/image/upload/v1752876044/notes-assets/images/GitHub-Actions-Certification-Create-a-Docker-Action/github-actions-successful-workflow-testing-action.jpg) View detailed logs for build and script outputs: ![The image shows a GitHub Actions interface with a successful workflow run for "testing-action," displaying job setup details and steps like "Checkout Repository" and "Post PR Comment."](https://kodekloud.com/kk-media/image/upload/v1752876045/notes-assets/images/GitHub-Actions-Certification-Create-a-Docker-Action/github-actions-successful-workflow-testing-action-2.jpg) *** ## 12. Reviewing the Bot Comment Your PR will now contain an automated comment with a thank-you message and a Giphy GIF. 🎉 *** ## 13. Links and References * [Giphy Random GIF Endpoint](https://developers.giphy.com/docs/api/endpoint#random) * [GitHub Create an Issue Comment API](https://docs.github.com/rest/issues/comments#create-an-issue-comment) * [jq Manual](https://stedolan.github.io/jq/) * [GitHub Actions](https://docs.github.com/actions) Congratulations! You have built a reusable Docker Action that integrates external APIs to enhance your pull request workflow. Consider publishing this action to the [GitHub Marketplace](https://docs.github.com/actions/creating-actions/publishing-actions-in-github-marketplace) next.