Customized Tracing

Concept Disctiption

A distributed call chain tracking records the service calling sequence, but developers also need information about link invocation inside a microservice to describe a complete call chain. In this way, they can locate error and identify potential performance problems more easily.

Prerequisites

• To use the customized dotting function, you need to configure and set the Java Chassis microservice call chain.

Precautions

• The customized dotting that uses the @Span annotation can only be called using the thread that calls Java Chassis.
• To add the @Span annotation, you must use the Bean method of Spring. Otherwise, you need to configure dotting following the procedure in this section.

Customized Dotting Call Chain

This function integrates Zipkin and provides the @Span annotation to customize dotting for the method you want to track. Java Chassis automatically tracks all the methods that track the @Span annotation, associating the local method call information with the call information between services.

Procedure:

Add dependency

For microservices based on ServiceComb Java Chassis, add the following content to pom.xml

    <dependency>
      <groupId>org.apache.servicecomb</groupId>
      <artifactId>tracing-zipkin</artifactId>
    </dependency>

Enable customized dotting

Addthe @EnableZipkinTracing annotation to the application portal or the Spring configuration class:

@SpringBootApplication
@EnableZipkinTracing
public class ZipkinSpanTestApplication {
  public static void main(String[] args) {
    SpringApplication.run(ZipkinSpanTestApplication.class);
  }
}

Customize dotting

Add the @Span annotation to the method that requires dotting customization:

@Component
public class SlowRepoImpl implements SlowRepo {
  private static final Logger logger = LoggerFactory.getLogger(SlowRepoImpl.class);

  private final Random random = new Random();

  @Span
  @Override
  public String crawl() throws InterruptedException {
    logger.info("in /crawl");
    Thread.sleep(random.nextInt(200));
    return "crawled";
  }
}

In this way, Zipkin-based customized dotting is enabled using the @Span annotation.

Customize reported data

The call chain reported by customized dotting contains the following pieces of data:

• span name which is the full name of the annotated method by default.

• call.path which is the signature of the annotated method by default.

  For example, the data reported in SlowRepoImp is as follows:

key	value
span name	crawl
call.path	public abstract java.lang.String org.apache.servicecomb.tests.tracing.SlowRepo.crawl() throws java.lang.InterruptedException

To customize reported data, you can specify customized parameters:

  public static class CustomSpanTask {
    @Span(spanName = "transaction1", callPath = "startA")
    public String invoke() {
      return "invoke the method";
    }
  }