Monitor Express.js with OpenTelemetry

By combining OpenTelemetry with Express.js, you can collect and export telemetry data, including traces, metrics, and logs, to gain insight into the behavior and performance of your application.

• What is Express.js?
• What is OpenTelemetry?
• Express.js instrumentation
• Usage
• Uptrace
• What's next?

What is Express.js?

Express.js is a fast and minimalist web application framework for Node.js, a JavaScript runtime. It simplifies the development of web applications and APIs by providing a robust set of features and utilities, while maintaining a lightweight and unobtrusive approach.

Express.js is widely recognized for its simplicity, flexibility, and extensibility, making it a popular choice for building server-side applications in Node.js.

What is OpenTelemetry?

OpenTelemetry is an open source observability framework for OpenTelemetry tracing, logs, and metrics.

OpenTelemetry allows developers to collect and export telemetry data in a vendor-agnostic manner. With OpenTelemetry, you can instrument your application once and then add or change vendors without changing the instrumentation, for example, here is a list of popular DataDog competitors that support OpenTelemetry.

OpenTelemetry is available for most programming languages and provides interoperability across different languages and environments.

Express.js instrumentation

Using the OpenTelemetry Node.js library, you can easily add distributed tracing capabilities to your Express.js applications.

To instrument an Express.js app, you need to install OpenTelemetry Node.js SDK and available instrumentations:

# Using npm
npm install @opentelemetry/sdk-node @opentelemetry/api @opentelemetry/auto-instrumentations-node

# Using yarn
yarn add @opentelemetry/sdk-node @opentelemetry/api @opentelemetry/auto-instrumentations-node

You can let OpenTelemetry to instrument your application automatically or do it explicitly by installing required instrumentations:

# Using npm
npm install @opentelemetry/instrumentation-http @opentelemetry/instrumentation-express

# Using yarn
yarn add @opentelemetry/instrumentation-http @opentelemetry/instrumentation-express

Usage

After installing OpenTelemetry, you need to configure OpenTelemetry SDK to export data to an OpenTelemetry backend for strorage and visualization.

'use strict'

const otel = require('@opentelemetry/api')
const { BatchSpanProcessor } = require('@opentelemetry/sdk-trace-base')
const { Resource } = require('@opentelemetry/resources')
const { NodeSDK } = require('@opentelemetry/sdk-node')
const { OTLPTraceExporter } = require('@opentelemetry/exporter-trace-otlp-http')
const { AWSXRayIdGenerator } = require('@opentelemetry/id-generator-aws-xray')
const { HttpInstrumentation } = require('@opentelemetry/instrumentation-http')
const { ExpressInstrumentation } = require('@opentelemetry/instrumentation-express')

const dsn = process.env.UPTRACE_DSN
console.log('using dsn:', dsn)

const exporter = new OTLPTraceExporter({
  url: 'http://localhost:14318/v1/traces',
  headers: { 'uptrace-dsn': dsn },
  compression: 'gzip',
})
const bsp = new BatchSpanProcessor(exporter, {
  maxExportBatchSize: 1000,
  maxQueueSize: 1000,
})

const sdk = new NodeSDK({
  spanProcessor: bsp,
  resource: new Resource({
    'service.name': 'myservice',
    'service.version': '1.0.0',
  }),
  idGenerator: new AWSXRayIdGenerator(),
  instrumentations: [new HttpInstrumentation(), new ExpressInstrumentation()],
})
sdk.start()

To avoid potential issues, it is strongly recommended to put the OpenTelemetry initialization code into a separate file called otel.js and use the --require flag to load the tracing code before the application code:

# JavaScript
node --require ./otel.js app.js

# TypeScript
ts-node --require ./otel.ts app.ts

See OpenTelemetry Express.js example for details.

Uptrace

Uptrace is a Grafana alternative that supports distributed tracing, metrics, and logs. You can use it to monitor applications and troubleshoot issues.

Uptrace comes with an intuitive query builder, rich dashboards, alerting rules with notifications, and integrations for most languages and frameworks.

Uptrace can process billions of spans and metrics on a single server and allows you to monitor your applications at 10x lower cost.

In just a few minutes, you can try Uptrace by visiting the cloud demo (no login required) or running it locally with Docker. The source code is available on GitHub.

What's next?

By integrating OpenTelemetry with Express.js, you can gain insight into your application's distributed traces, OpenTelemetry metrics, and logs. This helps you understand the behavior of your Express.js application across multiple services or microservices, and facilitates troubleshooting and performance optimization.

Next, instrument more operations to get a more detailed picture. Try to prioritize network calls, disk operations, database queries, error and logs.

You can also create your own instrumentations using OpenTelemetry JS Tracing API.

• OpenTelemetry Django
• OpenTelemetry Falcon