aws-lambda-fastify

Introduction

Inspired by the AWSLABS aws-serverless-express library tailor made for the Fastify web framework.

No use of internal sockets, makes use of Fastify's inject function.

Installation

$ npm install aws-lambda-fastify

Example

app.js

const fastify = require('fastify');

const app = fastify();
app.get('/', (request, reply) => reply.send({ hello: 'world' }));

if (require.main !== module) {
  // called directly i.e. "node app"
  app.listen(3000, (err) => {
    if (err) console.error(err);
    console.log('server listening on 3000');
  });
} else {
  // required as a module => executed on aws lambda
  module.exports = app;
}

When executed in your lambda function we don't need to listen to a specific port, so we just export the app in this case. The lambda.js file will use this export.

When you execute your Fastify application like always, i.e. node app.js (the detection for this could be require.main === module), you can normally listen to your port, so you can still run your Fastify function locally.

lambda.js

const awsLambdaFastify = require('aws-lambda-fastify')
const app = require('./app');

const proxy = awsLambdaFastify(app)
// or
// const proxy = awsLambdaFastify(app, { binaryMimeTypes: ['application/octet-stream'] })

exports.handler = proxy;
// or
// exports.handler = (event, context, callback) => proxy(event, context, callback);
// or
// exports.handler = (event, context) => proxy(event, context);
// or
// exports.handler = async (event, context) => proxy(event, context);

Hint

The original lambda event and context are passed via headers and can be used like this:

app.get('/', (request, reply) => {
  const event = JSON.parse(decodeURIComponent(request.headers['x-apigateway-event']))
  const context = JSON.parse(decodeURIComponent(request.headers['x-apigateway-context']))});
  // ...
})

Considerations

• For apps that may not see traffic for several minutes at a time, you could see cold starts
• Stateless only
• API Gateway has a timeout of 29 seconds, and Lambda has a maximum execution time of 15 minutes.