Introduction to Spring Cloud Sleuth

What is Spring Cloud Sleuth?

Spring Cloud Sleuth is a distributed tracing solution for Spring applications. It provides the necessary tools to trace requests as they traverse through microservices, making it easier to debug and monitor the performance of your applications. By integrating with platforms like Zipkin or OpenTracing, Sleuth helps in visualizing the flow of requests and understanding bottlenecks in your architecture.

Key Features of Spring Cloud Sleuth

• Automatic instrumentation of Spring components.
• Propagation of tracing context across threads and microservices.
• Integration with Zipkin for visualizing traces.
• Support for various logging systems.
• Customization of trace and span IDs.

Getting Started with Spring Cloud Sleuth

To start using Spring Cloud Sleuth, you need to add it as a dependency in your Spring Boot project. This can be done by including the following in your pom.xml if you are using Maven:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-sleuth</artifactId>
</dependency>
                

After adding the dependency, you can start your Spring Boot application, and Sleuth will automatically instrument your application for tracing.

Basic Configuration

Spring Cloud Sleuth works out-of-the-box with sensible defaults. However, you might want to customize some settings. This can be done in your application.yml or application.properties file. Here’s an example of how to customize the sampling rate:

spring:
  sleuth:
    sampler:
      probability: 0.5
                

Tracing Requests

Once you have set up Spring Cloud Sleuth, it automatically creates a unique trace ID for each request. This trace ID is propagated across different services. You can log the trace ID in your application logs. Here’s an example of how you can log the current trace ID:

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.cloud.sleuth.Tracer;

@RestController
public class MyController {
    
    private final Logger logger = LoggerFactory.getLogger(MyController.class);

    @Autowired
    private Tracer tracer;

    @GetMapping("/trace")
    public String trace() {
        logger.info("Current Trace ID: {}", tracer.currentSpan().context().traceId());
        return "Check the logs for the Trace ID!";
    }
}
                

When you hit the /trace endpoint, it logs the current Trace ID which you can use to correlate logs across different services.

Visualizing Traces with Zipkin

To visualize your traces, you can integrate Spring Cloud Sleuth with Zipkin. First, you need to add the Zipkin dependency to your project:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-zipkin</artifactId>
</dependency>
                

Next, in your application.yml, configure the Zipkin server URL:

spring:
  zipkin:
    base-url: http://localhost:9411
                

Start your Zipkin server and run your application. You can now visit the Zipkin UI (http://localhost:9411) to see the traces being recorded.

Conclusion

Spring Cloud Sleuth is a powerful tool for monitoring and debugging microservices. By providing automatic tracing of requests and integration with Zipkin, it helps developers gain insights into the performance of their applications. With this introduction, you should be able to set up Spring Cloud Sleuth in your application and start tracking requests across your services.