OpenTelemetry tracing with nodejs and express

In this post I’ll go through a simple example on how to setup OpenTelemetry tracing in a nodejs express application.

Hello world express

// index.js
const express = require("express");

const app = express();
const port = 3000;

app.get("/", (req, res) => {
  res.send("Hello World!");
});

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`);
});

Needed packages

First we need to add the OpenTelemetry api and sdk package

yarn add @opentelemetry/api @opentelemetry/sdk-node

To instrument express, incoming and outgoing http requests we use the express and http instrumentation libraries.

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

And lastly we add the otlp grpc tracing exporter.

yarn add @opentelemetry/exporter-trace-otlp-grpc

Setup tracing

// tracing.js
const OpenTelemetry = require("@opentelemetry/sdk-node");
const Resources = require("@opentelemetry/resources");
const SemanticConventions = require("@opentelemetry/semantic-conventions");
const InstrumentationHttp = require("@opentelemetry/instrumentation-http");
const InstrumentationExpress = require("@opentelemetry/instrumentation-express");
const ExporterTraceOtlpGrpc = require("@opentelemetry/exporter-trace-otlp-grpc");

const sdk = new OpenTelemetry.NodeSDK({
  resource: new Resources.Resource({
    [SemanticConventions.SemanticResourceAttributes.SERVICE_NAME]: "my-service",
  }),
  traceExporter: new ExporterTraceOtlpGrpc.OTLPTraceExporter({
    // url is optional and can be omitted - default is localhost:4317
    url: process.env["OTEL_EXPORTER_OTLP_ENDPOINT"] || undefined,
  }),
  instrumentations: [
    new InstrumentationHttp.HttpInstrumentation(),
    new InstrumentationExpress.ExpressInstrumentation(),
  ],
});

sdk.start();

Run the express server

To configure and start the tracing sdk we can use nodes -r/--require flag to preload our tracing module.

node -r ./tracing.js index.js

Now every request will be traced and exported to the configured otlp receiver.