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Jonathan Mourtada
Jonathan Mourtada

Posted on • Originally published at mourtada.se on

OpenTelemetry tracing with nodejs and express

#opentelemetry #node #express #javascript

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}`); });
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Needed packages

First we need to add the OpenTelemetry api and sdk package

yarn add @opentelemetry/api @opentelemetry/sdk-node
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To instrument express, incoming and outgoing http requests we use the express and http instrumentation libraries.

yarn add @opentelemetry/instrumentation-http @opentelemetry/instrumentation-express
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And lastly we add the otlp grpc tracing exporter.

yarn add @opentelemetry/exporter-trace-otlp-grpc
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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();
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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
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Now every request will be traced and exported to the configured otlp receiver.

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