06 – Generating Traces (Hands-On with Applications)

Learning Objectives

• Auto-instrument a sample application in your preferred language.
• Configure OTel SDK exporters to the Collector.
• Verify traces arrive in Grafana Explore.

Language Options (choose one to start)

Node.js (Express)

npm init -y && npm i express @opentelemetry/sdk-node @opentelemetry/auto-instrumentations-node @opentelemetry/exporter-trace-otlp-grpc

tracing.js:

const { NodeSDK } = require('@opentelemetry/sdk-node');
const { getNodeAutoInstrumentations } = require('@opentelemetry/auto-instrumentations-node');
const { OTLPTraceExporter } = require('@opentelemetry/exporter-trace-otlp-grpc');

const exporter = new OTLPTraceExporter({ url: 'grpc://localhost:4317' });
const sdk = new NodeSDK({
  traceExporter: exporter,
  instrumentations: [getNodeAutoInstrumentations()],
  resource: undefined,
});
sdk.start();

app.js:

require('./tracing');
const express = require('express');
const app = express();
app.get('/hello', async (_req, res) => res.send('world'));
app.listen(8080, () => console.log('app on :8080'));

Python (Flask)

pip install flask opentelemetry-sdk opentelemetry-exporter-otlp opentelemetry-instrumentation-flask

app.py:

from flask import Flask
app = Flask(__name__)
@app.get('/hello')
def hello():
    return 'world'
if __name__ == '__main__':
    app.run(host='0.0.0.0', port=8080)

Run with auto instrumentation:

opentelemetry-instrument \ 
  --traces_exporter otlp \ 
  --exporter_otlp_endpoint http://localhost:4318 \ 
  --service_name flask-app python app.py

Go (net/http)

go get go.opentelemetry.io/otel/sdk@latest \ 
       go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp@latest

main.go (minimal example sending OTLP HTTP to collector):

package main
// initialize tracer provider with OTLP HTTP exporter to http://localhost:4318/v1/traces
// implement /hello handler; ensure spans are created via HTTP instrumentation or manual spans.

Java (agent)

Download the agent JAR (opentelemetry-javaagent) and run:

JAVA_TOOL_OPTIONS="-javaagent:/path/opentelemetry-javaagent.jar" \
OTEL_TRACES_EXPORTER=otlp \
OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4318 \
OTEL_SERVICE_NAME=spring-app \
java -jar app.jar

Hands-on Lab

1. Start the stack from Section 5.
2. Run your app; generate traffic (curl http://localhost:8080/hello).
3. In Grafana → Explore → Data Source: Tempo → search by service name or use TraceQL.

Deliverables

• One running app emitting traces visible in Grafana Explore.

Quiz (Self-check)

• What environment variables configure the OTLP endpoint for your SDK/agent?
• What’s the difference between auto and manual instrumentation?

Resources

• Language-specific OTel instrumentation libraries
• OTel Semantic Conventions

Visual: End-to-End Tracing Flow