@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

pnpm add @rdub/og-lambda

Usage

Config file

Create .og-lambda.json in your project:

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

Then deploy:

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

Environment variables override config file values.

Configuration options

| 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 |

Using the screenshot function directly

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 <meta property="og:image"> 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

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