index.js

require('signalfx-tracing').init({
  service: 'rxjs-fiddle-backend',
  url: `http://${process.env.SIGNALFX_AGENT_HOST}:9080/v1/trace`,
});

const express = require("express");
const cors = require("cors");
const { omit } = require('lodash');
const fetch = require('node-fetch');
const echo = require("./functions/echo");
const runFiddle = require("./functions/run-fiddle");

const functions = { echo, "run-fiddle": runFiddle };

const meta = {
  env: process.env.ENVIRONMENT_NAME,
  version: process.env.API_VERSION
};

const app = express();
const port = process.env.PORT || 8080;
app.use(express.json());
app.use(cors());

app.use('/v2/trace', (req, res) => {
  fetch('https://ingest.us0.signalfx.com/v2/trace', {
    method: req.method,
    body: JSON.stringify(req.body),
    headers:  { 
      ...omit(req.headers, 'host', 'origin', 'referer'), 
      'X-SF-TOKEN': process.env.SIGNALFX_TOKEN 
    }
  })
  .then(traceResponse => traceResponse.json())
  .then(traceJson => res.send(traceJson))
  .catch(err => res.status(500).json({ error: err.message }))
})

Object.keys(functions).forEach(name => {
  app.all(`/${name}`, (req, res) => {
    const ret = functions[name]({ data: req.body });
    if (ret instanceof Promise) {
      ret.then(response => res.json({ response, meta }));
    } else {
      res.json({ response: ret, meta });
    }
  });
});

app.listen(port);