10. Sending spans to Zipkin

	Important
	spring-cloud-sleuth-stream is deprecated and should no longer be used. If spring-cloud-sleuth-zipkin is on the classpath then the app will generate and collect Zipkin-compatible traces. By default it sends them via HTTP to a Zipkin server on localhost (port 9411). If you depend on spring-rabbit or spring-kafka your app will send traces to a broker instead of http.

By default if you add spring-cloud-starter-zipkin as a dependency to your project, when the span is closed, it will be sent to Zipkin over HTTP. The communication is asynchronous. You can configure the URL by setting the spring.zipkin.baseUrl property as follows:

spring.zipkin.baseUrl: https://192.168.99.100:9411/

If you want to find Zipkin via service discovery it’s enough to pass the Zipkin’s service id inside the URL. If you want to disable this feature just set spring.zipkin.discoveryClientEnabled to false. Example for `zipkinserver service id:

spring.zipkin.baseUrl: http://zipkinserver/

When this Discovery Client feature is enabled, Sleuth uses LoadBalancerClient to find the URL of the Zipkin Server. It means that you can set up the load balancing configuration e.g. via Ribbon.

zipkinserver:
  ribbon:
    ListOfServers: host1,host2

If you have web, rabbit or kafka together on the classpath, you might need to pick the means by which you would like to send spans to zipkin. To do that just set either web, rabbit or kafka to the spring.zipkin.sender.type property. Example for web:

spring.zipkin.sender.type: web

To customize the RestTemplate that sends spans to Zipkin via HTTP, you can register the ZipkinRestTemplateCustomizer bean.

@Configuration
class MyConfig {
	@Bean ZipkinRestTemplateCustomizer myCustomizer() {
		return new ZipkinRestTemplateCustomizer() {
			@Override
			void customize(RestTemplate restTemplate) {
				// customize the RestTemplate
			}
		};
	}
}

If, however, you would like to control the full process of creating the RestTemplate object, you will have to create a bean of zipkin2.reporter.Sender type.

	@Bean Sender myRestTemplateSender(ZipkinProperties zipkin,
			ZipkinRestTemplateCustomizer zipkinRestTemplateCustomizer) {
		RestTemplate restTemplate = mySuperCustomRestTemplate();
		zipkinRestTemplateCustomizer.customize(restTemplate);
		return myCustomSender(zipkin, restTemplate);
	}