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This guide uses the example application in HTML & javascript provided below, but the steps to instrument your own application should be broadly the same. Here is an overview of what we will be doing.

  • Install the required OpenTelemetry libraries
  • Initialize a global tracer
  • Initialize and register a span exporter

This is a very simple guide, if you'd like to see more complex examples go to examples/tracer-web

Copy the following file into an empty directory and call it index.html.

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>Document Load Plugin Example</title>
  <base href="/">
  <!--
    https://www.w3.org/TR/trace-context/
    Set the `traceparent` in the server's HTML template code. It should be
    dynamically generated server side to have the server's request trace Id,
    a parent span Id that was set on the server's request span, and the trace
    flags to indicate the server's sampling decision
    (01 = sampled, 00 = notsampled).
    '{version}-{traceId}-{spanId}-{sampleDecision}'
  -->
  <meta name="traceparent" content="00-ab42124a3c573678d4d8b21ba52df3bf-d21f7bc17caa5aba-01">
  <meta name="viewport" content="width=device-width, initial-scale=1">
</head>
<body>
  Example of using Web Tracer with document load plugin with console exporter and collector exporter
</body>
</html>

Installation

To create traces in the browser, you will need @opentelemetry/web, and the plugin @opentelemetry/plugin-document-load:

npm init -y
npm install --save @opentelemetry/web @opentelemetry/instrumentation-document-load @opentelemetry/context-zone

Initialization and Configuration

Create a empty file called document-load.js and add the following code to your html right before the body end tag:

<script type="text/javascript" src="document-load.js"></script>

We will add some code that will trace the document load timings and output those as OpenTelemetry Spans.

Creating a Tracer Provider

Add the following code to the document-load.js to create a tracer provider, which brings the plugin to trace document load:

import { WebTracerProvider } from '@opentelemetry/web';
import { DocumentLoadInstrumentation } from '@opentelemetry/instrumentation-document-load';
import { ZoneContextManager } from '@opentelemetry/context-zone';
import { registerInstrumentations } from '@opentelemetry/instrumentation';

const provider = new WebTracerProvider();

provider.register({
  // Changing default contextManager to use ZoneContextManager - supports asynchronous operations - optional
  contextManager: new ZoneContextManager(),
});

// Registering instrumentations / plugins
registerInstrumentations({
  instrumentations: [
    new DocumentLoadInstrumentation(),
  ],
});

In the following we will use parcel as web application bundler, but you can of course also use any other build tool.

Run

npx parcel index.html

and open the development webserver (e.g. at http://localhost:1234) to see if your code works.

There will be no output of traces yet, for this we need to add an exporter

Creating a Console Exporter

To export traces, modify document-load.js so that it matches the following code snippet:

import { ConsoleSpanExporter, SimpleSpanProcessor } from '@opentelemetry/tracing';
import { WebTracerProvider } from '@opentelemetry/web';
import { DocumentLoadInstrumentation } from '@opentelemetry/instrumentation-document-load';
import { ZoneContextManager } from '@opentelemetry/context-zone';
import { registerInstrumentations } from '@opentelemetry/instrumentation';

const provider = new WebTracerProvider();
provider.addSpanProcessor(new SimpleSpanProcessor(new ConsoleSpanExporter()));

provider.register({
  // Changing default contextManager to use ZoneContextManager - supports asynchronous operations - optional
  contextManager: new ZoneContextManager(),
});

// Registering instrumentations / plugins
registerInstrumentations({
  instrumentations: [
    new DocumentLoadInstrumentation(),
  ],
});

Now, rebuild your application and open the browser again. In the console of the developer toolbar you should see some traces being exporterd:

{
  "traceId": "ab42124a3c573678d4d8b21ba52df3bf",
  "parentId": "cfb565047957cb0d",
  "name": "documentFetch",
  "id": "5123fc802ffb5255",
  "kind": 0,
  "timestamp": 1606814247811266,
  "duration": 9390,
  "attributes": {
    "component": "document-load",
    "http.response_content_length": 905
  },
  "status": {
    "code": 0
  },
  "events": [
    {
      "name": "fetchStart",
      "time": [
        1606814247,
        811266158
      ]
    },
    {
      "name": "domainLookupStart",
      "time": [
        1606814247,
        811266158
      ]
    },
    {
      "name": "domainLookupEnd",
      "time": [
        1606814247,
        811266158
      ]
    },
    {
      "name": "connectStart",
      "time": [
        1606814247,
        811266158
      ]
    },
    {
      "name": "connectEnd",
      "time": [
        1606814247,
        811266158
      ]
    },
    {
      "name": "requestStart",
      "time": [
        1606814247,
        819101158
      ]
    },
    {
      "name": "responseStart",
      "time": [
        1606814247,
        819791158
      ]
    },
    {
      "name": "responseEnd",
      "time": [
        1606814247,
        820656158
      ]
    }
  ]
}