trace-ws.js

#!/usr/bin/env node --unhandled-rejections=strict

/*
 * Copyright Elasticsearch B.V. and other contributors where applicable.
 * Licensed under the BSD 2-Clause License; you may not use this file except in
 * compliance with the BSD 2-Clause License.
 */

// A small example showing Elastic APM tracing of the 'ws' package.
//
// Currently Elastic APM will create a span for `ws.send()` calls.
// For tracing spans to be created, there must be an active transaction.
// Typically, a transaction is automatically started for incoming HTTP
// requests to a Node.js server. However, because this script is not running
// an HTTP server, we manually start transactions in our websocket server and
// client. More details at:
// https://www.elastic.co/guide/en/apm/agent/nodejs/current/custom-transactions.html

const apm = require('../').start({ // elastic-apm-node
  serviceName: 'example-trace-ws'
})

const WebSocket = require('ws')
const PORT = 4567

// Server
const wss = new WebSocket.Server({ port: PORT })
wss.on('connection', function (ws) {
  ws.on('message', function (message) {
    console.log('server on "message": %j', message)
    const tserver = apm.startTransaction('tserver')
    ws.send('pong')
    tserver.end()
  })
})

// Client
const ws = new WebSocket('ws://localhost:' + PORT)
ws.on('open', function () {
  const tclient = apm.startTransaction('tclient')
  console.log('client: send "ping"')
  ws.send('ping', function () {
    console.log('client: "ping" has been sent')
  })
  console.log('client: send "ring"')
  ws.send('ring')
  tclient.end()
})
ws.on('message', function (message) {
  console.log('client on "message": %j', message)
  wss.close()
})