Using Cheerio in a serverless environment like AWS Lambda is a common approach for running lightweight web scraping or HTML processing tasks. AWS Lambda is particularly well-suited for this because you only pay for the execution time you consume, and you don't need to manage any servers.
Here's how you can set up a serverless function on AWS Lambda to use Cheerio:
Step 1: Set up your AWS Lambda function
- Log in to the AWS Management Console.
- Go to the AWS Lambda service.
- Click on "Create function".
- Choose "Author from scratch".
- Provide a function name, e.g.,
cheerioScraper. - Select a runtime that supports Node.js, e.g.,
Node.js 14.x. - Choose or create an execution role that has basic Lambda permissions.
- Click on "Create function".
Step 2: Write the Lambda function code
You can either write your Lambda function code directly in the inline code editor in AWS Lambda console or package your code with dependencies and upload it.
Here is an example of a simple Lambda function code that uses Cheerio to scrape data from an HTML string:
// Import the required AWS SDK for JavaScript.
const AWS = require('aws-sdk');
// Import the Cheerio library.
const cheerio = require('cheerio');
exports.handler = async (event) => {
// Example HTML string to parse with Cheerio.
const html = '<!DOCTYPE html><html><head><title>Page Title</title></head><body><h1>This is a Heading</h1><p>This is a paragraph.</p></body></html>';
// Load the HTML string with Cheerio.
const $ = cheerio.load(html);
// Extract the text of the heading using Cheerio.
const headingText = $('h1').text();
// Return the extracted text.
return {
statusCode: 200,
body: JSON.stringify({
heading: headingText
}),
};
};
Step 3: Include Cheerio in your deployment package
To include Cheerio in your deployment package, you will need to create a package with all the necessary node modules.
- Create a new directory on your local machine for your Lambda function code.
- Initialize a new npm package with
npm init. - Install Cheerio with
npm install cheerio. - Place your Lambda function code in a file named
index.js(or any other name you prefer). - Zip the contents of the directory, including the
node_modulesdirectory,package.json,package-lock.json, and yourindex.js.
Step 4: Upload your function code
- In the AWS Lambda console, navigate to your function.
- Under the "Function code" section, select "Upload from" → ".zip file".
- Upload the zip file that contains your function and the
node_modulesdirectory.
Step 5: Set up your Lambda function’s trigger
Depending on your use case, you might want to trigger your Lambda function via an API Gateway, an S3 event, or a scheduled event (like a cron job). Set up the relevant trigger in the AWS Lambda console.
Step 6: Test your Lambda function
- In the AWS Lambda console, select your function.
- Click on the "Test" tab.
- Configure a test event in the format that your function expects.
- Click the "Test" button to execute your function.
Your Lambda function will now run and use Cheerio to parse the provided HTML content. You can monitor the execution result and logs in the AWS Lambda console to ensure it's working as expected.
Note on Cold Starts
When using AWS Lambda, be aware of cold starts, which can add latency to the execution time of your function if it hasn't been used recently. For web scraping tasks that are sensitive to execution time, consider keeping the function warm by invoking it periodically or using provisioned concurrency.
