lambda-api-helpers

Set of utilities to implement APIs using AWS Lambda. The package provides the following features:

1. Simplify the signature of the Lambda handler
2. Error Handling & set of common HTTP errors to be used as Node JS Errors

1. Simplify the signature of the Lambda handler

Usage

import asLambdaHandler from '@ori-sh/lambda-api';

export const handler = asLambdaHandler(async request => ({
  greeting: `Hello ${request.body?.name ?? 'World'}!`
}));

Request

type HttpRequest = {
  method: 'GET' | 'HEAD' | 'PUT' | 'POST' | 'DELETE' | 'PATCH'
  body: JsonObject | undefined
  queryParams: Record<string, string | undefined>
  pathParams: Record<string, string | undefined>
  headers: Record<string, string | undefined>
}

Response

type HttpResponse = JsonObject | undefined

2. Error Handling & set of common HTTP errors to be used as Node JS Errors

When using the asLambdaHandler helper it's automatically wires error handling for you.
This will automatically catch any unexpected error thrown in the handler and normalize it as 500 HTTP response.

Additionally, it will catch any error extending HttpError and normalize it as HTTP response. The following errors are available out of the box:

BadRequest - 400

The server could not understand the request. Can happen when request failed validation or received in a malformed format.

Unauthorized - 401

Request has not been applied because it lacks valid authentication credentials. Can happen when the Authorization token is expired, invalid or missing.

Forbidden - 403

The server understood the request but authenticated user isn't authorized to perform it. Happens when the user don't have sufficient permissions to perform the request.

NotFound - 404

The requested resource has not been found. Can happen when querying resource with wrong id or resource that has been deleted.

Conflict - 409

The server can not process your request due a conflict with a existing result. Might happen when trying to create a resource which already exist.

TooManyRequests - 429

The user has sent too many requests in a given amount of time. Might happen when there is a throttling policy applied.

Note that the response error will expose stack traces unless explicitly setting NODE_ENV to 'production'. Make sure to add the NODE_ENV environment variable in production to prevent leakage of the server internals with stack traces.

Usage Example:

import asLambdaHandler, { NotFound } from '@ori-sh/lambda-api';

export const handler = asLambdaHandler(async request => {
  const item = queryItemFromDatabase(request.pathParams.id);
  // If no item found in the database a 404 status HTTP response will be returned. 
  if (item === null || item === undefined)
    throw new NotFound(`No item with the id "${request.pathParams.id}"`)
  return item;
});