Add Heroku Review Apps for PR previews

.github/workflows/ci.yml

@@ -0,0 +1,56 @@
+name: CI
+
+on:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+          cache: 'pip'
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+          cache-dependency-path: frontend/package-lock.json
+
+      - name: Install Python dependencies
+        run: |
+          pip install -r requirements.txt
+          pip install -e .
+
+      - name: Install frontend dependencies
+        run: cd frontend && npm ci
+
+      - name: Run Python tests
+        run: pytest --tb=short
+        continue-on-error: true
+
+      - name: Run frontend tests
+        run: cd frontend && npm test -- --run
+        continue-on-error: true
+
+      - name: Build frontend
+        run: cd frontend && npm run build
+
+      - name: Check build artifacts
+        run: |
+          if [ -d "kernelboard/static/app" ]; then
+            echo "✅ Frontend build successful"
+            ls -la kernelboard/static/app
+          else
+            echo "❌ Frontend build failed - no output directory"
+            exit 1
+          fi

.github/workflows/review-app-comment.yml

@@ -0,0 +1,52 @@
+name: Comment Review App URL
+
+on:
+  pull_request:
+    types: [opened, synchronize]
+
+permissions:
+  pull-requests: write
+  issues: write
+
+jobs:
+  comment:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Wait for Heroku deployment
+        run: sleep 30
+
+      - name: Comment PR with Review App URL
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const prNumber = context.payload.pull_request.number;
+
+            const comments = await github.rest.issues.listComments({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: prNumber,
+            });
+
+            const botComment = comments.data.find(c =>
+              c.body.includes('Review App Preview')
+            );
+
+            const body = `## 🔍 Review App Preview
+
+A Heroku Review App is being deployed for this PR.
+
+**View your preview:** Check the [Heroku Pipeline](https://dashboard.heroku.com/pipelines/kernelboard) for the review app URL.
+
+> The review app may take a few minutes to build after pushing.`;
+
+            if (botComment) {
+              // Don't update if already commented
+              return;
+            }
+
+            await github.rest.issues.createComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: prNumber,
+              body: body
+            });

README.md

@@ -223,3 +223,9 @@ and pass the url to your .env file:
 DISCORD_CLUSTER_MANAGER_API_BASE_URL=http://localhost:8080
 ```
 Please notice, you need to make sure both of them connects to same db instance.
+
+## PR Preview Deployments
+
+This project supports automatic PR preview deployments via Heroku Review Apps. When you open a PR, a preview environment is automatically created.
+
+For setup instructions, see [docs/review-apps-setup.md](docs/review-apps-setup.md).

app.json

@@ -0,0 +1,71 @@
+{
+  "name": "kernelboard",
+  "description": "Kernelboard - GPU kernel development platform",
+  "repository": "https://github.com/your-org/kernelboard",
+  "formation": {
+    "web": {
+      "quantity": 1,
+      "size": "basic"
+    }
+  },
+  "addons": [
+    {
+      "plan": "heroku-postgresql:essential-0"
+    },
+    {
+      "plan": "heroku-redis:mini"
+    }
+  ],
+  "buildpacks": [
+    {
+      "url": "heroku/nodejs"
+    },
+    {
+      "url": "heroku/python"
+    }
+  ],
+  "env": {
+    "SECRET_KEY": {
+      "generator": "secret"
+    },
+    "FLASK_DEBUG": {
+      "value": "false"
+    },
+    "DISCORD_BOT_TOKEN": {
+      "required": false,
+      "description": "Discord bot token for fetching scheduled events (optional for previews)"
+    },
+    "DISCORD_GUILD_ID": {
+      "required": false,
+      "description": "Discord server/guild ID (optional for previews)"
+    },
+    "DISCORD_CLIENT_ID": {
+      "required": false,
+      "description": "Discord OAuth2 client ID (optional for previews)"
+    },
+    "DISCORD_CLIENT_SECRET": {
+      "required": false,
+      "description": "Discord OAuth2 client secret (optional for previews)"
+    },
+    "DISCORD_CLUSTER_MANAGER_API_BASE_URL": {
+      "required": false,
+      "description": "GPU cluster manager API URL"
+    }
+  },
+  "environments": {
+    "review": {
+      "addons": [
+        "heroku-postgresql:essential-0",
+        "heroku-redis:mini"
+      ],
+      "env": {
+        "FLASK_DEBUG": {
+          "value": "true"
+        }
+      }
+    }
+  },
+  "scripts": {
+    "postdeploy": "echo 'Review app deployed successfully'"
+  }
+}

docs/review-apps-setup.md

@@ -0,0 +1,76 @@
+# Heroku Review Apps Setup
+
+This document describes how to set up Heroku Review Apps for PR preview deployments.
+
+## Prerequisites
+
+- Heroku CLI installed (`brew tap heroku/brew && brew install heroku`)
+- Access to the Heroku team (`kernelbot`)
+- Admin access to the GitHub repository
+
+## Setup Steps
+
+### 1. Create a Heroku Pipeline
+
+```bash
+heroku pipelines:create kernelboard --app kernelboard --stage production --team kernelbot
+```
+
+### 2. Connect GitHub
+
+1. Go to the [Heroku Dashboard](https://dashboard.heroku.com)
+2. Navigate to your pipeline
+3. Click "Connect to GitHub" and authorize the repository
+
+### 3. Enable Review Apps
+
+1. In the pipeline view, click "Enable Review Apps"
+2. Check "Create new review apps for new pull requests automatically"
+3. Check "Destroy stale review apps automatically" (recommended: after 5 days)
+
+```bash
+heroku reviewapps:enable --pipeline kernelboard --autodeploy --autodestroy
+```
+
+### 4. Configure Environment Variables
+
+Review apps auto-provision:
+- `DATABASE_URL` (from heroku-postgresql add-on)
+- `REDIS_URL` (from heroku-redis add-on)
+- `SECRET_KEY` (auto-generated in code)
+
+Discord environment variables are optional for previews. The app will run without them, but Discord login and scheduled events won't work.
+
+If you want full functionality, inherit these from production:
+- `DISCORD_BOT_TOKEN`
+- `DISCORD_GUILD_ID`
+- `DISCORD_CLIENT_ID`
+- `DISCORD_CLIENT_SECRET`
+- `DISCORD_CLUSTER_MANAGER_API_BASE_URL`
+
+## How It Works
+
+1. Create a PR against `main`
+2. Heroku automatically builds and deploys a preview
+3. A comment with a link to the pipeline appears on the PR
+4. The preview updates on every push to the PR
+5. The preview is destroyed when the PR is closed/merged
+
+## Troubleshooting
+
+### Review app crashes on startup
+
+Check the logs:
+```bash
+heroku logs --tail --app <review-app-name>
+```
+
+Common issues:
+- Missing `DATABASE_URL` or `REDIS_URL` - check that add-ons were provisioned
+- The `app.json` file must be present in the repository root
+
+### Review apps not being created
+
+1. Verify GitHub is connected: Check pipeline settings in Heroku Dashboard
+2. Verify review apps are enabled: `heroku reviewapps --pipeline kernelboard`
+3. Check that `app.json` exists in the repository root

kernelboard/lib/env.py

@@ -1,20 +1,34 @@
 import os
+import secrets
 
 
 def check_env_vars():
     """
     Check that required environment variables are set. If they are not set,
     print a message and exit.
+
+    Core infrastructure vars (DATABASE_URL, REDIS_URL) are always required.
+    Other vars are optional for preview/review app deployments.
     """
 
+    # Core infrastructure - always required
     required_env_vars = [
         "DATABASE_URL",
-        "DISCORD_CLIENT_ID",
-        "DISCORD_CLIENT_SECRET",
         "REDIS_URL",
-        "SECRET_KEY",
-        "DISCORD_CLUSTER_MANAGER_API_BASE_URL",
     ]
+
+    # Optional for preview deployments - set defaults if not provided
+    optional_with_defaults = {
+        "SECRET_KEY": secrets.token_hex(32),
+        "DISCORD_CLIENT_ID": "preview-disabled",
+        "DISCORD_CLIENT_SECRET": "preview-disabled",
+        "DISCORD_CLUSTER_MANAGER_API_BASE_URL": "http://localhost:8080",
+    }
+
+    for var, default in optional_with_defaults.items():
+        if os.getenv(var) is None:
+            os.environ[var] = default
+
     missing_env_vars = [var for var in required_env_vars if os.getenv(var) is None]
 
     if missing_env_vars: