It works with Application Load Balancer!

[nabilfreeman]

Hey there, I was interested in trying out ALB instead of API Gateway for performance reasons.

I managed to get it working with the following code:

const serverless = (event, context) => {
	const app = Express();

	const binaryMimeTypes = [
		'application/json',
	];
	const server = AWSServerlessExpress.createServer(app, null, binaryMimeTypes);

	// Sometimes we receive encoded stuff in the url.
	// So we need to decode this to get Express parsing things properly.
	// We used to run this through Elastic Beanstalk and then API Gateway, and they decoded it for us.
	// Now we are using more custom stuff and DIY is required.

	// this is the home for our parsed query data.
	const query = {};

	// merge the raw query into one object.
	// it can come from different sources depending on API Gateway or Application Load Balancer.
	const raw_query = {
		...(event.query || {}),
		...(event.queryStringParameters || {}),
	};

	// decode everything back into utf-8 text.
	for (const key in raw_query) {
		const formatted_key = decodeURIComponent(key);

		query[formatted_key] = decodeURIComponent(raw_query[key]);
	}

	// set the parsed query back onto the event.
	event.query = query;
	event.queryStringParameters = query;

	return AWSServerlessExpress.proxy(server, event, context);
};

The trick was parsing the encoded query parts, annoyingly ALB did this automatically.

I set them back onto both queryStringParameters (ALB) and query (API Gateway) so it's compatible with both event types.

Do you think it would make sense to merge the decodeURIComponent stuff into the library?

It seems to be harmless if things are already decoded.

[emilionavarro]

Nice job man! I'm trying to do the same thing for ELB now. This helps a whole bunch!

[brett-vendia]

Nice! This is natively supported in v4