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/organizer'

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/organizer'

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/organizer'

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/organizer'

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/organizer'

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/organizer'

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 helper functions as well as the metadata function as following. These configurations might be useful for other Cloudomium libraries such as CDK constructs.

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

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