index.js

const port = process.env.PORT || 3000
const upstream_uri = process.env.UPSTREAM_URI || 'http://worldclockapi.com/api/json/utc/now'
const service_name = process.env.SERVICE_NAME || 'test-1-v1'

const express = require('express')
const app = express()
const request = require('request-promise-native')

app.get('/', async(req, res) => {

	const begin = Date.now()

	// Do Bad Things
	createIssues(req, res)

	// Forward Headers for tracing
	const headers = forwardTraceHeaders(req)

	let up
	try {
		up = await request({
			url: upstream_uri,
			headers: headers
		})
	} catch (error) {
		up = error
	}
	const timeSpent = (Date.now() - begin) / 1000 + "secs"

	res.end(`${service_name} - ${timeSpent}\n${upstream_uri} -> ${up}`)
})

app.listen(port, () => {
	console.log(`${service_name} listening on port ${port}!`)
})



function forwardTraceHeaders(req) {
	incoming_headers = [
		'x-request-id',
		'x-b3-traceid',
		'x-b3-spanid',
		'x-b3-parentspanid',
		'x-b3-sampled',
		'x-b3-flags',
		'x-ot-span-context',
		'x-dev-user',
		'fail'
	]
	const headers = {}
	for (let h of incoming_headers) {
		if (req.header(h))
			headers[h] = req.header(h)
	}
	return headers
}



function createIssues(req, res) {
	// Look at the "fail %" header to increase chance of failure
	// Failures cascade, so this number shouldn't be set too high (under 0.3 is good)
	const failPercent = Number(req.header('fail')) || 0
	console.log(`failPercent: ${failPercent}`)
	if (Math.random() < failPercent) {
		res.status(500).end()
	}
}