Distributed tracing helps you follow a request as it flows through multiple microservices. It’s useful for:

  • Debugging latency issues
  • Understanding service dependencies
  • Observing bottlenecks in request paths

Traces are usually composed of spans:

  • Trace ID: identifies the full request flow.
  • Span ID: identifies a single operation within the trace.
  • Parent Span ID: connects spans into a tree.

2. Configure Zipkin

In application.properties (or application.yml):

spring.application.name=tracing-demo
spring.sleuth.sampler.probability=1.0
spring.zipkin.base-url=http://localhost:9411/
spring.zipkin.enabled=true
  • spring.sleuth.sampler.probability=1.0 → send all traces.
  • spring.zipkin.base-url → Zipkin server URL.

3. Example Controller

package com.example.tracingdemo;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class DemoController {

    @GetMapping("/hello")
    public String hello() {
        return "Hello from Spring Boot with Zipkin!";
    }
}

4. Run Zipkin

The easiest way is via Docker:

docker run -d -p 9411:9411 openzipkin/zipkin

5. Integrate Jaeger (Optional)

Spring Cloud Sleuth supports Jaeger too.

Add dependency in build.gradle:

implementation 'io.opentracing.contrib:opentracing-spring-jaeger-cloud-starter:3.2.0'

Configure Jaeger in application.properties:

spring.application.name=tracing-demo
spring.sleuth.sampler.probability=1.0

# Jaeger settings
JAEGER_SERVICE_NAME=tracing-demo
JAEGER_AGENT_HOST=localhost
JAEGER_AGENT_PORT=6831

Run Jaeger using Docker:

docker run -d --name jaeger \
  -e COLLECTOR_ZIPKIN_HTTP_PORT=9411 \
  -p 5775:5775/udp \
  -p 6831:6831/udp \
  -p 6832:6832/udp \
  -p 5778:5778 \
  -p 16686:16686 \
  -p 14268:14268 \
  -p 9411:9411 \
  jaegertracing/all-in-one:1.47

6. Test Tracing

  1. Run your Spring Boot app.
  2. Hit endpoint: curl http://localhost:8080/hello
  3. Check traces in Zipkin or Jaeger UI.

You should see a trace for the /hello request.

✅ Key Points:

  • Spring Cloud Sleuth automatically instruments your app and sends traces.
  • Zipkin is lightweight and easy to run.
  • Jaeger is more full-featured and integrates well with Kubernetes.

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