healthcheck-middleware

Node.js Express Middleware for healthcheck

A heathcheck can be a valuable tool in the arsenal of disaster recovery and overall performance. A typical healthcheck is a simple status code 200 "Ok" response from a REST endpoint.

Todays infrastructure, microservices or applications (e.g. Lerna) exsisting of a bundle of microservices, provide a challenge to proper monitoring of services. With that being said, a simple "Ok" means nothing other that the app is standing with a reachable point. In an express app, that is not difficult to achieve.

Well what if you wanted to know the status of a service connection like a Message Queue Broker. Yes you can have a dashboard letting you know on the Broker side what the status of the service is. What if we wanted to have more granular status form an implementing service. How about add a service status to a secured healthcheck? Sounds good to me.

The POST verb should be properly secured behind authentication. Exposing internal configurations to external unsecured audiences can lead to potential security issues. Don't Do It

We've provided a simple ping to handle generic GET request to the healthcheck

usage

Ping

$ curl http://localhost:3001/health

response

Ok

Healthcheck Verbose (requires authentication)

$ curl -X POST http://localhost:3001/health

response

{
	"appName": "API",
	"timestamp": "2020-11-20T23:46:49.251Z",
	"server": 12000,
	"region": "us-east-1",
	"services": [
		{
			"id": "56969530-87f2-4a27-a297-12e4c90b04e9",
			"name": "broker",
			"timestamp": "2020-11-20T23:46:49.252Z",
			"startTime": "2020-11-20T23:46:47.371Z",
			"upTime": "1881",
			"status": "Ok",
			"data": {
				"host": "e-2f0c9slkj-2sj-b4e1-f3b7564asdf3998.mq.us-east-1.amazonaws.com",
				"cluster_name": "broker",
				"platform": "Erlang/OTP 23.0.3",
				"product": "RabbitMQ",
				"version": "3.8.6"
			}
		}
	]
}

This tool has become a vital tool for us, we've decided to share it with you.

Typescript

import { express } from 'express'
import { createServer } from 'http'
import { healthcheck } from '@basementscripts/healthcheck-middleware'

const app = express()

// apply middleware
app.use(
	healthcheck({
		pid: process.pid,
		appName: 'api',
		region: 'us-east-1'
	})
)
const server = createServer(app)

add a service agent to the healthcheck

import { registerStatusAgent } from '@basementscripts/healthcheck-middleware'
import amqp, { Connection } from 'amqplib'

export interface BrokerConnectionOptions {
	name?: string
	host: string
}

export const connect = async ({
	name = 'broker',
	host
}: BrokerConnectionOptions): Promise<void> => {
	const agent = registerStatusAgent({
		name,
		data: {
			host
		}
	})

	try {
		const { connection }: Connection = await amqp.connect(host)
		agent.up(connection.serverProperties)
	} catch (e) {
		agent.down(e)
	}
}

example health check output

{
	"appName": "API",
	"timestamp": "2020-11-20T23:46:49.251Z",
	"server": 12000,
	"region": "us-east-1",
	"services": [
		{
			"id": "56969530-87f2-4a27-a297-12e4c90b04e9",
			"name": "broker",
			"timestamp": "2020-11-20T23:46:49.252Z",
			"startTime": "2020-11-20T23:46:47.371Z",
			"upTime": "1881",
			"status": "Ok",
			"data": {
				"host": "e-2f0c9slkj-2sj-b4e1-f3b7564asdf3998.mq.us-east-1.amazonaws.com",
				"cluster_name": "broker",
				"platform": "Erlang/OTP 23.0.3",
				"product": "RabbitMQ",
				"version": "3.8.6"
			}
		}
	]
}

Authentication

import { express, Request } from 'express'
import { createServer } from 'http'
import { healthcheck } from '@basementscripts/healthcheck-middleware'
import validateAuthToken from '@services/auth/validateAuthToken'

const app = express()

const headhcheckAuthenticationHandler = (headers: Request['headers']) => {
	const token = headers.authorization.replace(/Bearer /, '') // extract bearer token
	return validateAuthToken(token)
}

// apply middleware
app.use(
	healthcheck({
		pid: process.pid,
		appName: 'api',
		region: 'us-east-1',
		authenticate: headhcheckAuthenticationHandler
	})
)
const server = createServer(app)

Extended Configuration

Additional configuration options can be added to the originating healthcheck object

import { express, Request } from 'express'
import { createServer } from 'http'
import { healthcheck } from '@basementscripts/healthcheck-middleware'
import validateAuthToken from '@services/auth/validateAuthToken'

const app = express()

const headhcheckAuthenticationHandler = (headers: Request['headers']) => {
	const token = headers.authorization.replace(/Bearer /, '') // extract bearer token
	if (token) {
		return validateAuthToken(token)
	}
	throw new Error('Unauthorized')
}

// apply middleware
app.use(
	healthcheck({
		pid: process.pid,
		appName: 'api',
		region: 'us-east-1',
		cluster: 'api-ecs-cluster-us-east-1',
		service: 'api-ecs-service-us-east-1',
		authenticate: headhcheckAuthenticationHandler,
		...etc
	})
)
const server = createServer(app)