Cloudomium Lambda

This project is a set of opinionated simple tools for easier serverless development on AWS Lambda.

Before / After The Lambda Handler

There are methods called before and after in organizer classes. These methods add middleware functions to be called right before or right after executing the handler function. Usually, the middlewares which added to be called before the handler are for processing the request. On the other hand, the middlewares which added to be called after the handler are for processing the response.

Parameter	Type	Required	Description
middleware	function	true	a middleware function that implements Middleware interface

To define the handler function, there is a method called execute

Parameter	Type	Required	Description
handler	function	true	a handler function that implements Handler interface

const handler = new HttpLambda()
    .before(middlewareA())
    .after(middlewareB())
    .execute(async (event, context) => {
        return { statusCode: 204 }
    })

Built-in Middlewares

There are various built-in middlewares. Also, you can easily build your own middlewares by creating a function that implements Middleware interface.

Authentication

This middleware adds an authentication and authorization layer in front of the Lambda handler function. While the jwt token is for authentication part, check function is for authorization.

Parameter	Type	Required	Description
jwt	object	true	jsonwebtoken instance
jwtOptions	object	false	official options for jsonwebtoken instance
secret	secret	true	the secret value for signing and verifying tokens
header	string	false	header key for tokens, default value is authorization
mustSignIn	boolean	false	flag to determine authentication requirement
check	function	false	function for validating claims inside the token

import jwt from 'jsonwebtoken'
import { HttpLambda } from '@cloudomium/lambda'

const handler = new HttpLambda()
    .before(authMiddleware({ jwt, secret: 'my secret', mustSignedIn: true }), (error, type) => console.error(type, error))
    .execute(async (event, context) => {
        return { statusCode: 204 }
    })

CORS

This middleware adds a simple CORS support to the response. It's better (also cheaper) to solve CORS in front of Lambda, instead of invoking one

Parameter	Type	Required	Description
origins	string[]	false	allowed origins. default value is "*"
headers	string[]	false	allowed headers
methods	string[]	false	allowed methods
credentials	boolean	false	flag to allow credentials

import { HttpLambda } from '@cloudomium/lambda'

const handler = new HttpLambda()
    .before(corsMiddleware({ origins: ['http://localhost:9000'] }), (error, type) => console.error(type, error))
    .execute(async (event, context) => {
        return { statusCode: 204 }
    })

JSON Body Parser

This middleware adds a support for JSON payload.

Parameter	Type	Required	Description
base64	boolean	false	flag for base64 encoding
compressed	boolean	false	flag for gzip compression

import { HttpLambda } from '@cloudomium/lambda'

const handler = new HttpLambda()
    .before(jsonMiddleware(), (error, type) => console.error(type, error))
    .execute(async (event, context) => {
        return { statusCode: 204 }
    })

HTTP Validator

This middleware adds a validation support for input and / or output data

Parameter	Type	Required	Description
body	object	false	ZodError model for body
queryString	object	false	ZodError model for queryString
pathParameters	object	false	ZodError model for pathParameters
headers	object	false	ZodError model for headers
onError	function	false	Error handling function

import { HttpLambda } from '@cloudomium/lambda'

const handler = new HttpLambda()
    .before(validate({ body: z.object({ name: z.string() }) }), (error, type) => console.error(type, error))
    .execute(async (event, context) => {
        return { statusCode: 204 }
    })

S3 Fetch

This middleware downloads objects from S3 and parse them accordingly right before processing S3BucketEvent

Parameter	Type	Required	Description
s3.client	S3 or S3Client	true	S3 client
s3.command	GetObjectCommand	true	S3's GetObjectCommand class
base64	boolean	false	flag for base64 encoding
compressed	boolean	false	flag for gzip compression
json	boolean	false	flag for json data

import { S3Lambda } from '@cloudomium/lambda'

const handler = new S3Lambda()
    .before(s3FetchMiddleware({ s3: { client, command: GetObjectCommand } }), (error, type) => console.error(type, error))
    .execute(async (event, context) => {
        // void
    })

Callback Waits For Empty Event Loop

This middleware manages the context flag for empty event loop behavior

Parameter	Type	Required	Description
wait	boolean	false	wait flag

import { SqsLambda } from '@cloudomium/lambda'

const handler = new HttpLambda()
    .before(callbackWaitsForEmptyEventLoopMiddleware(), (error, type) => console.error(type, error))
    .execute(async (event, context) => {
        return { statusCode: 204 }
    })

Attaching Metadata

You can define various settings and attach them to your Lambda organizer by calling the metadata function as following. These configurations might be useful for other Cloudomium libraries such as CDK constructs.

import { ResourceType, SqsLambda } from '@cloudomium/lambda'

const handler = new HttpLambda()
    .metadata('cdk.lambda.function', { memorySize: 128, timeout: 30 })
    .execute(async (event, context) => {
        return { statusCode: 204 }
    })