trace-1074.js

const propagation = require('@opencensus/propagation-b3');

const tracer = require('@google-cloud/trace-agent').start({
  rootSpanNameOverride: ((path) => `http://helloworld${path}`),
  ignoreUrls: ['/metrics', '/api_version'],
  samplingRate: 0.1,
  propagation: new propagation.B3Format(),
  disableUntracedModulesWarning: true
});

const log = console.log;
const axios = require('axios');
const bodyParser = require('body-parser');
const express = require('express');

const PORT = 8080;
const app = express();

// // Purposely lose context
// let cbs = [];
// setInterval(() => {
//   cbs.forEach(cb => cb());
//   cbs = [];
// }, 10);
//
// app.use((req, res, next) => {
//   cbs.push(next);
// });

app.use(bodyParser.json());

app.get('/', async (req, res) => {
  log('======');
  log(req.headers);
  if (tracer.getCurrentRootSpan().getTraceContext()) {
      log(tracer.getCurrentRootSpan().getTraceContext());
  } else {
      log("No trace context");
  }
  const prev = req.query.prev || '';
  const [ss, sns] = process.hrtime();
  const input = parseInt(req.query.n);
  const output = input >= 2 ? (await Promise.all([
    axios.get(`http://localhost:${PORT}/?prev=${prev}%20${input}&n=${input - 1}`),
    axios.get(`http://localhost:${PORT}/?prev=${prev}%20${input}&n=${input - 2}`)
  ])).reduce((a, b) => a + parseInt(b.data), 0) : input;
  const [es, ens] = process.hrtime();
  if (!prev) { // An outermost request
    const time = 1e9 * (es - ss) + ens - sns;
    console.log(`Running Time: ${time}`);
  }
  res.send(`${output}`);
});

app.get('/shutdown', () => {
  process.exit();
});

app.listen(PORT);