JetKit/CDK
An anti-framework for building cloud-native serverless applications.
This module provides convenient tools for writing Lambda functions, RESTful API views, and generating cloud infrastructure with AWS CDK.
Motivation
Frameworkless web applications.
We want to build maintainable and scalable cloud-first applications, with cloud resources generated from application code.
Using AWS CDK we can automate generating API Gateway routes and Lambda functions from class and function metadata.
Each class or function view is a self-contained Lambda function that only pulls in the dependencies needed for its functioning, keeping startup times low and applications modular.
Documentation
Guides and API reference can be found at https://jetkit.dev/docs/.
Super Quickstart
Use this monorepo project template: typescript-cdk-template.
Installation
npm install @jetkit/cdkSynopsis
API View
Combine related functionality and routes into a single Lambda function bundle.
import { HttpMethod } from "@aws-cdk/aws-apigatewayv2"
import { badRequest, methodNotAllowed } from "@jdpnielsen/http-error"
import { ApiView, SubRoute, ApiEvent, ApiResponse, ApiViewBase, apiViewHandler } from "@jetkit/cdk-runtime"
@ApiView({
path: "/album",
})
export class AlbumApi extends ApiViewBase {
// define POST /album handler
@SubRoute({ methods: [HttpMethod.POST] })
async post() {
return "Created new album"
}
// custom endpoint in the view
// routes to the ApiView function
@SubRoute({
path: "/{albumId}/like", // will be /album/123/like
methods: [HttpMethod.POST, HttpMethod.DELETE],
})
async like(event: ApiEvent): ApiResponse {
const albumId = event.pathParameters?.albumId
if (!albumId) throw badRequest("albumId is required in path")
const method = event.requestContext.http.method
// POST - mark album as liked
if (method == HttpMethod.POST) return `Liked album ${albumId}`
// DELETE - unmark album as liked
else if (method == HttpMethod.DELETE) return `Unliked album ${albumId}`
// should never be reached
else return methodNotAllowed()
}
}
// Not required but lets you omit specifying the `entry` path to this file for convenience.
export const handler = apiViewHandler(__filename, AlbumApi)
// If using ES modules
// export const handler = apiViewHandlerEs(import.meta, AlbumApi)Handler Function With Route
import { HttpMethod } from "@aws-cdk/aws-apigatewayv2"
import { Lambda, ApiEvent } from "@jetkit/cdk-runtime"
// a simple standalone function with a route attached
export async function topSongsHandler(event: ApiEvent) {
return JSON.stringify(event.headers)
}
// define route and lambda properties
Lambda({
path: "/top-songs",
methods: [HttpMethod.GET],
})(topSongsHandler)
// If using ES modules:
// LambdaEs(import.meta, { path: "/top-songs" })(topSongsHandler)
// alternate, uglier way of writing the same thing
const topSongsFuncInner = Lambda({
path: "/top-songs-inner",
methods: [HttpMethod.GET],
// this function name should match the exported name
// or you must specify the exported function name in `handler`
})(async function topSongsFuncInner(event: ApiEvent) {
return JSON.stringify(event.headers)
})
export { topSongsFuncInner }CDK Stack
To start from scratch:
npm install -g aws-cdk
cdk init app --language typescript
npm install @jetkit/cdk @aws-cdk/core @aws-cdk/aws-apigatewayv2See the guide for more details.
To deploy your stack:
cdk deployTo generate API Gateway routes and Lambda function handlers from your application code:
import { CorsHttpMethod, HttpApi } from "@aws-cdk/aws-apigatewayv2"
import { Duration, Stack, StackProps, App } from "@aws-cdk/core"
import { ResourceGeneratorConstruct, ApiViewCdk } from "@jetkit/cdk"
import { topSongsHandler, AlbumApi } from "./test/sampleApp"
export class InfraStack extends Stack {
constructor(scope: App, id: string, props?: StackProps) {
super(scope, id, props)
// create API Gateway
const httpApi = new HttpApi(this, "Api", {
corsPreflight: {
allowHeaders: ["Authorization"],
allowMethods: [CorsHttpMethod.ANY],
allowOrigins: ["*"],
maxAge: Duration.days(10),
},
})
// transmute your app code into infrastructure
new ResourceGeneratorConstruct(this, "Generator", {
resources: [
// supply your functions and view classes here
topSongsHandler,
// can add additional lambda attributes here if desired
ApiViewCdk({ memorySize: 1024, bundling: { minify: true }})(AlbumApi)
],
httpApi,
})
}
}How It Works
This library provides decorators that can be attached to view classes, methods, and functions. The decorator attaches metadata in the form of options for constructing the Lambda function and optionally API Gateway routes.
It also includes some convenient CDK L3 constructs to generate the Lambda functions and API Gateway routes from your decorated application code.
Local Development
AWS SAM supports running CDK applications locally (in beta).