Use middleware to remove redundancy in AWS Lambda handlers.

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@sailplane/lambda-utils - Lambda handler middleware


There's a lot of boilerplate in Lambda handlers. This collection of utility functions leverage the great Middy library to add middleware functionality to Lambda handlers. You can extend it with your own middleware.
This is part of the sailplane library of utilities for AWS Serverless in Node.js.


Middy gives you a great start as a solid middleware framework, but by itself you are still repeating the middleware registrations on each handler, its exception handler only works with errors created by the http-errors package, and you still have to format your response in the shape required by API Gateway.
LambdaUtils takes Middy further and is extendable so that you can add your own middleware (authentication & authorization, maybe?) on top of it.
Used with API Gateway, the included middlewares:
  • Set CORS headers
  • Normalize incoming headers to mixed-case
  • If incoming content is JSON text, replaces event.body with parsed object
  • Ensures that event.queryStringParameters and event.pathParameters are defined, to avoid TypeErrors
  • Ensures that handler response is formatted properly as a successful API Gateway result
- Unique to LambdaUtils!
- Simply return what you want as the body of the HTTP response
  • Catch http-errors exceptions into proper HTTP responses
  • Catch other exceptions and return as HTTP 500
- Unique to LambdaUtils!
- Besides providing better feedback to the client, not throwing an exception out of your handler means that your
  instance will not be destroyed and suffer a cold start on the next invocation
  • Leverages async syntax


See the doc site for usage and examples.