Distributed Tracing in Spring Boot using OpenTelemetry + Jaeger (2025 Guide)

This guide helps you understand:

✅ What is distributed tracing
✅ How to enable OpenTelemetry in Spring Boot
✅ How Jaeger receives spans
✅ What is the difference between OTEL vs Prometheus
✅ Complete ready-to-run example with Docker Compose
✅ Architecture diagrams
✅ README for your project

---

1. What is Distributed Tracing?

Modern microservices often involve multiple services communicating with each other:

Client → API Gateway → Auth Service → Order Service → Inventory Service

Debugging such systems with only logs is extremely difficult.

Distributed Tracing solves this by:

✔ Tracking a request end-to-end
✔ Showing how long each service took
✔ Identifying bottlenecks
✔ Detecting where a failure occurs

OpenTelemetry (OTEL) is the standard for collecting such traces.

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2. What is OpenTelemetry (OTEL)?

OpenTelemetry is an open-source CNCF standard for:

• Traces

• Metrics

• Logs

In your Spring Boot app, OTEL:

1. Creates spans

2. Stores them briefly in memory

3. Exports them through OTLP protocol

4. Sends to a backend like Jaeger, Tempo, Zipkin, etc.

✔ OTEL uses a push model

This means:

Your application sends data OUT to Jaeger, like this:

Spring Boot (OTEL SDK)
     ↓ (push)
Jaeger Collector

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3. What is Jaeger?

Jaeger is an open-source distributed tracing system.

In local mode (all-in-one):

• Collector

• Query

• UI

• Storage

are all in one container.

Jaeger stores data:

• In memory (in local mode)

• Elastic / Cassandra / ClickHouse / etc. (in production)

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4. Architecture Diagram (Spring Boot → OTEL → Jaeger)

Client
  |
  v
Spring Boot App
  |
  | creates spans
  v
OTel SDK
  |
  | batches spans (memory buffer)
  v
OTLP Exporter
  |
  | pushes spans
  v
Jaeger Collector (4317/4318)
  |
  v
Jaeger Storage (Memory)
  |
  v
Jaeger UI (16686)

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5. How Does OTEL Export Data? (Important)

👉 OTEL does not store long-term data
👉 OTEL only batches spans in memory for milliseconds
👉 OTEL pushes spans to Jaeger via OTLP

There is no polling.

✔ Jaeger never calls your app
✔ Your app always pushes the data

---

6. What is Prometheus?

Prometheus is used for:

• Metrics (CPU, memory, request_count, latency, etc.)

• Alerting

• Time-series storage

Prometheus follows a pull model:

Prometheus scrapes /actuator/prometheus endpoint

✔ Prometheus calls your Spring Boot endpoint

✔ Your app does NOT push data

✔ Prometheus stores metrics on disk

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7. OTEL vs Prometheus (VERY IMPORTANT)

Feature	OpenTelemetry	Prometheus
Purpose	Tracing (request flow)	Metrics (performance)
Data Type	Spans, traces, logs	Time-series metrics
Collection Model	Push (App → Jaeger)	Pull (Prometheus → App)
How It Works	OTEL sends trace data instantly	Prometheus periodically scrapes
What It Shows	End-to-end request timing	CPU, memory, errors, latency
Storage	Jaeger (memory/DB)	Prometheus TSDB
UI	Jaeger UI	Grafana
Ideal Use	Microservice debugging	Monitoring & alerting

✔ Both used together in production

You use:

➡ OTEL + Jaeger for tracing
➡ Prometheus + Grafana for metrics

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8. Spring Boot Example (Tracing /hello endpoint)

Your controller:

@GetMapping("/hello")
public String hello() {
    Span span = tracer.spanBuilder("custom-span").startSpan();
    span.addEvent("processing-hello");

    try { Thread.sleep(50); } catch(Exception ignored) {}

    span.end();
    return "Hello with tracing!";
}

Every request generates a trace visible in Jaeger.

---

9. Docker Compose — Spring Boot + Jaeger

version: "3.8"

services:

  spring-app:
    build: .
    image: springboot-tracing-demo:latest
    container_name: springboot-tracing
    environment:
      - OTEL_SERVICE_NAME=springboot-tracing-demo
      - OTEL_EXPORTER_OTLP_ENDPOINT=http://jaeger:4318
      - OTEL_EXPORTER_OTLP_PROTOCOL=http/protobuf
      - OTEL_TRACES_EXPORTER=otlp
    ports:
      - "8080:8080"
    depends_on:
      - jaeger

  jaeger:
    image: jaegertracing/all-in-one:1.57
    container_name: jaeger
    ports:
      - "16686:16686"
      - "4317:4317"
      - "4318:4318"

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10. Source code

https://github.com/kkvinodkumaran/springboot-tracing-demo-complete