Schildwall

Schildwall is a service to manage security and accessibility of API-Networks. It aims to provide a modular, simple way of building complex gateways for big APIs. It supports

• Custom Middleware
• Multiple Endpoints

installation

npm i --save @vampyreio/schildwall

How To Use

The example can be ran using 'npm run-script example' and starts a proxy server on port 8000 with an endpoint

• /test/ which points to localhost:8888

// gateway.class.ts

import { ListenerErrorHandler, GatewayApp, MasterGateway } from '@vampyreio/schildwall';
import { HeaderMiddleware } from './app/middleware';

@GatewayApp({
    log: true,
    listenerErrorHandler: new ListenerErrorHandler,
    endpoints: [
        { endpoint: 'http://localhost:58', name: 'local58' },
        { endpoint: 'http://google.com', name: 'google' },
    ],
    middlewares: [new HeaderMiddleware()],
})
export class Gateway extends MasterGateway { }

// index.ts
import { Gateway } from './gateway.class';

const gateway = new Gateway();

async function bootstrap() {
    const server = await gateway.init();
    server.listen(3000);
}

If the gateway now runs on localhost:8000, a request to Google with path /search would be made with

GET /google/search => GET http://google.com/search
GET /local58/entity/abcde => GET http://localhost:58/entity/abcde

because the first parameter of the path will be mapped onto the provided endpoint list and cut from the incoming url.

Middleware

Defining a Middleware

Middleware can be attached to the gateway easily. A Middleware contains methods that control what it should do on startup, on shutdown and on execution. It has access to the servers request and response via the ctx object.

to let a header block the request and answer it itself with an error, it's not required to set the answer manually. Schildwall provides Error Objects for all 4xx and 5xx errors. when such an error is thrown, an internal error handler does this itself. It will me overwritable in upcoming versions to allow manual error handling.

Middleware will be executed in the order of binding.

In upcoming versions, middlewares will be able to pass data to following middlewares.

import {Middleware, IGatewayContext, BadGatewayException} from '../lib';

/**
 * checks for a 'kill-me' header and if it is true, throw an exception
 */
class HeaderScanner extends Middleware {

    /**
     * executes when a request enters
     */
    public async execute(ctx: IGatewayContext): Promise<any> {
        if (ctx.request.headers['kill-me'] === 'true') {
            throw new BadGatewayException('kill-me header was found');
        }
    }

    /**
     * executes when a middleware is bound
     */
    public async start(): Promise<any> {
        // Setup, initialisation, precondition checking, ...
    }

    /**
     * executes when the server should stop
     */
    public async stop(): Promise<any> { 
        // Cleanup, stopping processes, deletions, ...
    }

}

Handle HTTP-Errors manually

If you want to futher manipulate how your gateway behaves when an error is thrown, you can insert a custom error handler. Error classes implement the MiddlewareErrorHandler which takes following parameters:

• errorCodeToCatch: number is the error code for which the error should be handled.
• execute: (ctx: IGatewayContext, error: HttpError) => Promise<void> is the handler itself.

In future versions, instead of a manual error code, an error class could be passed by a decorator function

import { GatewayApp, MasterGateway, ListenerErrorHandler, Middleware, IGatewayContext, BadGatewayException, MiddlewareErrorHandler, HttpError } from '../lib';

/**
 * handles 502 errors 
 */
class MyFiveZeroTwo implements MiddlewareErrorHandler {

    public errorCodeToCatch: number = 502;

    public async execute(ctx: IGatewayContext, error: HttpError) {

        ctx.response.write('There is actually text in this reply!');
        ctx.response.statusCode = 502;
        return ctx.response.end();

    }
}

@GatewayApp({
    log: true,
    listenerErrorHandler: new ListenerErrorHandler,
    endpoints: [
        { endpoint: 'http://localhost:3000', name: 'mock' }
    ],
    middlewares: [new HeaderScanner()],
    middlewareErrorHandlers: [new MyFiveZeroTwo()],
})
class Gateway extends MasterGateway { }

const gateway = new Gateway();
gateway.init().then((data) => {
    data.server.listen(8000);
});

API

Schildwall supports accessing and manipulating the gateway via an controlling API. Following routes are currently supported:

Miidleware

• GET /middlewares - Lists metadata about
• GET /middlewares/:middlewareId' - list metadata of a specific middleware
• POST /middleware/:middlewareId/toggle - starts or stops a middleware
• PATCH /middleware/:middlewareId - changes a middlewares settings
• DELETE /middleware/:middlewareId - removes a selected middlware

Endpoints

• GET /endpoints - Lists endpoints
• GET /endpoints/:endpointId - describes a single endpoint
• POST /endpoints - Creates a new Endpoint Params:

• endpoint: an url to a new endpoint
• name: is used as prefix in the gateway

Minimal with API

@GatewayApp({
    log: true,
    listenerErrorHandler: new ListenerErrorHandler,
    endpoints: [
        { endpoint: 'http://localhost:3000', name: 'mock' }
    ],
})
class Gateway extends MasterGateway { }

const gateway = new Gateway();
gateway.init().then((data) => {

    // create Server
    data.server.listen(8000);

    // create API
    const api = new GatewayApiServer(data.manager as ListenerManager).run(8081);
});

Error Handling