@rdub/og-lambda

Scheduled AWS Lambda for generating og:image screenshots. Takes a screenshot of a URL on a schedule and uploads it to S3.

Installation

``bash
pnpm add @rdub/og-lambda
`

Usage

$3

Create .og-lambda.json in your project:

`json
{
"stackName": "myproject-og",
"screenshotUrl": "https://mysite.com",
"s3Bucket": "my-bucket",
"s3Key": "og-image.jpg"
}
`

Then deploy:

`bash
og-lambda deploy
og-lambda status
og-lambda config # Show resolved configuration
`

Environment variables override config file values.

$3

| Config key | Env var | Default | Description |
|------------|---------|---------|-------------|
| screenshotUrl | SCREENSHOT_URL | (required) | URL to screenshot |
| s3Bucket | S3_BUCKET | (required) | S3 bucket for output |
| s3Key | S3_KEY | og-image.jpg | S3 key (path) for output |
| stackName | STACK_NAME | og-lambda | CloudFormation stack name |
| viewportWidth | VIEWPORT_WIDTH | 1200 | Screenshot width |
| viewportHeight | VIEWPORT_HEIGHT | 630 | Screenshot height |
| waitForSelector | WAIT_FOR_SELECTOR | - | CSS selector to wait for |
| waitForFunction | WAIT_FOR_FUNCTION | - | JS expression that must return truthy |
| waitForTimeout | WAIT_FOR_TIMEOUT | - | Extra ms to wait after load |
| quality | SCREENSHOT_QUALITY | 90 | JPEG quality (0-100) |
| scheduleRateMinutes | SCHEDULE_RATE_MINUTES | 60 | How often to run |
| timezone | TIMEZONE | - | Timezone for page rendering |

CDK-only options (env vars):

| Env var | Default | Description |
|---------|---------|-------------|
| LAMBDA_MEMORY | 2048 | Lambda memory in MB |
| LAMBDA_TIMEOUT_MINUTES | 2 | Lambda timeout |

$3

`typescript
import { takeScreenshot } from '@rdub/og-lambda'

const { buffer, contentType } = await takeScreenshot({
url: 'https://example.com',
width: 1200,
height: 630,
})
`

How it works

1. EventBridge triggers the Lambda on a schedule (default: hourly)
2. Lambda launches headless Chrome via @sparticuz/chromium
3. Takes a screenshot of the configured URL
4. Uploads the JPEG to S3 with public caching headers
5. Your site's points to the S3 URL

Requirements

- Node.js 20+
- AWS CDK CLI (npm install -g aws-cdk)
- AWS credentials configured
- S3 bucket with appropriate permissions

Architecture

`
EventBridge (hourly) → Lambda → Puppeteer/Chrome → S3 bucket
↓
Your site ← og:image URL ← Public URL
`

Development

`bash
pnpm install
pnpm build # Compile TypeScript
pnpm package # Bundle for Lambda
pnpm synth # Preview CloudFormation
pnpm deploy # Deploy to AWS
``