OpenTelemetry Express.js instrumentation

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?

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 that aims to standardize and simplify the collection, processing, and export of telemetry data from applications and systems.

OpenTelemetry supports multiple programming languages and platforms, making it suitable for a wide range of applications and environments.

OpenTelemetry enables developers to instrument their code and collect telemetry data, which can then be exported to various OpenTelemetry backends or observability platforms for analysis and visualization. The OpenTelemetry architecture follows a modular design with SDKs, APIs, and exporters as its core components.

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.

What is Uptrace

Uptrace is a OpenTelemetry APM that supports distributed tracing, metrics, and logs. You can use it to monitor applications and troubleshoot issues. For Node.js instrumentation, see the OpenTelemetry JavaScript guide and compare with top APM tools.

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.

DEV Community