index.js

/*
Copyright 2018 Google LLC

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

const port = process.env.PORT || 3000
const upstream_uri = process.env.UPSTREAM_URI || 'http://time.jsontest.com/'
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
    const headers = createIssues(req, res)

    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 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()
    }

    // Cascade trace headers and the fail and crash flags to upstream services
    // The trace headers are the only "Istio Specifc" thing your app needs to do!
    const headers = Object.assign({ 'fail': failPercent }, forwardTraceHeaders(req))

    return headers

    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'
        ]
        const headers = {}
        for (let h of incoming_headers) {
            if (req.header(h))
                headers[h] = req.header(h)
        }
        return headers
    }
}