Use listeners instead of custom callbacks

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/TraceScope.java

@@ -1,8 +1,6 @@
 package org.springframework.cloud.sleuth;
 
 import java.io.Closeable;
-import java.util.ArrayList;
-import java.util.List;
 
 import lombok.SneakyThrows;
 import lombok.Value;
@@ -33,11 +31,6 @@ public class TraceScope implements Closeable {
 	 */
 	private final Span savedSpan;
 
-	/**
-	 * List of callbacks to run on close.
-	 */
-	private List<Runnable> callbacks = new ArrayList<Runnable>();
-
 	@NonFinal
 	private boolean detached = false;
 
@@ -73,12 +66,6 @@ public class TraceScope implements Closeable {
 		return this.span;
 	}
 
-	public void register(Runnable callback) {
-		if (!this.callbacks .contains(callback)) {
-			this.callbacks.add(callback);
-		}
-	}
-
 	@Override
 	@SneakyThrows
 	public void close() {
@@ -86,13 +73,6 @@ public class TraceScope implements Closeable {
 			return;
 		}
 		this.detached = true;
-		for (Runnable callback : this.callbacks) {
-			try {
-				callback.run();
-			} catch (Throwable e) {
-				log.error("Error with callback on close", e);
-			}
-		}
 		Span cur = TraceContextHolder.getCurrentSpan();
 		if (cur != this.span) {
 			ExceptionUtils.error("Tried to close trace span " + this.span + " but " +

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/event/SpanStartedEvent.java

@@ -1,6 +1,8 @@
 package org.springframework.cloud.sleuth.event;
 
+import lombok.EqualsAndHashCode;
 import lombok.Value;
+
 import org.springframework.cloud.sleuth.Span;
 import org.springframework.context.ApplicationEvent;
 
@@ -8,6 +10,8 @@ import org.springframework.context.ApplicationEvent;
  * @author Spencer Gibb
  */
 @Value
+@EqualsAndHashCode(callSuper=false)
+@SuppressWarnings("serial")
 public class SpanStartedEvent extends ApplicationEvent {
 
 	private final Span span;

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/event/SpanStoppedEvent.java

@@ -1,6 +1,8 @@
 package org.springframework.cloud.sleuth.event;
 
+import lombok.EqualsAndHashCode;
 import lombok.Value;
+
 import org.springframework.cloud.sleuth.Span;
 import org.springframework.context.ApplicationEvent;
 
@@ -8,6 +10,8 @@ import org.springframework.context.ApplicationEvent;
  * @author Spencer Gibb
  */
 @Value
+@EqualsAndHashCode(callSuper=false)
+@SuppressWarnings("serial")
 public class SpanStoppedEvent extends ApplicationEvent {
 
 	private final Span span;

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/client/TraceWebClientAutoConfiguration.java

@@ -1,7 +1,8 @@
 package org.springframework.cloud.sleuth.instrument.web.client;
 
+import javax.annotation.PostConstruct;
+
 import org.springframework.beans.factory.annotation.Autowired;
-import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
@@ -9,8 +10,6 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.web.client.RestTemplate;
 
-import javax.annotation.PostConstruct;
-
 /**
  * @author Spencer Gibb
  */
@@ -42,8 +41,8 @@ public class TraceWebClientAutoConfiguration {
 
 		@PostConstruct
 		public void init() {
-			if (restTemplate != null) {
-				restTemplate.getInterceptors().add(traceRestTemplateInterceptor);
+			if (this.restTemplate != null) {
+				this.restTemplate.getInterceptors().add(this.traceRestTemplateInterceptor);
 			}
 		}
 	}

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/slf4j/Slf4jSpanStartedListener.java

@@ -17,9 +17,9 @@ public class Slf4jSpanStartedListener implements ApplicationListener<SpanStarted
 	@Override
 	public void onApplicationEvent(SpanStartedEvent event) {
 		Span span = event.getSpan();
-		//TODO: what log level?
-		log.info("Starting span: {}", span);
 		MDC.put(Trace.SPAN_ID_NAME, span.getSpanId());
 		MDC.put(Trace.TRACE_ID_NAME, span.getTraceId());
+		//TODO: what log level?
+		log.info("Starting span: {}", span);
 	}
 }

spring-cloud-sleuth-sample/src/main/java/org/springframework/cloud/sleuth/sample/SampleController.java

@@ -1,7 +1,11 @@
 package org.springframework.cloud.sleuth.sample;
 
+import java.util.Random;
+import java.util.concurrent.Callable;
+
 import lombok.SneakyThrows;
 import lombok.extern.slf4j.Slf4j;
+
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.context.embedded.EmbeddedServletContainerInitializedEvent;
 import org.springframework.cloud.sleuth.Span;
@@ -14,16 +18,13 @@ import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.client.RestTemplate;
 
-import java.util.Random;
-import java.util.concurrent.Callable;
-
 /**
  * @author Spencer Gibb
  */
 @Slf4j
 @RestController
 class SampleController implements
-		ApplicationListener<EmbeddedServletContainerInitializedEvent> {
+ApplicationListener<EmbeddedServletContainerInitializedEvent> {
 	@Autowired
 	private RestTemplate restTemplate;
 	@Autowired
@@ -36,7 +37,7 @@ class SampleController implements
 		final Random random = new Random();
 		Thread.sleep(random.nextInt(1000));
 
-		String s = restTemplate.getForObject("http://localhost:" + port + "/hi2",
+		String s = this.restTemplate.getForObject("http://localhost:" + this.port + "/hi2",
 				String.class);
 		return "hi/" + s;
 	}
@@ -64,19 +65,19 @@ class SampleController implements
 	@SneakyThrows
 	@RequestMapping("/traced")
 	public String traced() {
-		TraceScope scope = trace.startSpan("customTraceEndpoint", new AlwaysSampler());
+		TraceScope scope = this.trace.startSpan("customTraceEndpoint", new AlwaysSampler());
 		final Random random = new Random();
 		int millis = random.nextInt(1000);
 		log.info("Sleeping for {} millis", millis);
 		Thread.sleep(millis);
 
-		String s = restTemplate.getForObject("http://localhost:" + port + "/hi2", String.class);
+		String s = this.restTemplate.getForObject("http://localhost:" + this.port + "/hi2", String.class);
 		scope.close();
 		return "hi/" + s;
 	}
 
 	@Override
 	public void onApplicationEvent(EmbeddedServletContainerInitializedEvent event) {
-		port = event.getEmbeddedServletContainer().getPort();
+		this.port = event.getEmbeddedServletContainer().getPort();
 	}
 }

spring-cloud-sleuth-zipkin/src/main/java/org/springframework/cloud/sleuth/zipkin/ZipkinAutoConfiguration.java

@@ -7,9 +7,6 @@ import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
-import org.springframework.cloud.sleuth.IdGenerator;
-import org.springframework.cloud.sleuth.Sampler;
-import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
@@ -67,8 +64,8 @@ public class ZipkinAutoConfiguration {
 	}
 
 	@Bean
-	public ZipkinTrace zipkinTrace(ServerTracer serverTracer, Sampler<?> sampler, IdGenerator idGenerator, ApplicationEventPublisher publisher) {
-		return new ZipkinTrace(serverTracer, sampler, idGenerator, publisher);
+	public ZipkinSpanListener zipkinTrace(ServerTracer serverTracer) {
+		return new ZipkinSpanListener(serverTracer);
 	}
 
 	@Configuration

spring-cloud-sleuth-zipkin/src/main/java/org/springframework/cloud/sleuth/zipkin/ZipkinSpanListener.java

@@ -3,12 +3,10 @@ package org.springframework.cloud.sleuth.zipkin;
 import lombok.Data;
 import lombok.extern.apachecommons.CommonsLog;
 
-import org.springframework.cloud.sleuth.IdGenerator;
-import org.springframework.cloud.sleuth.Sampler;
 import org.springframework.cloud.sleuth.Span;
-import org.springframework.cloud.sleuth.TraceScope;
-import org.springframework.cloud.sleuth.trace.DefaultTrace;
-import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.cloud.sleuth.event.SpanStartedEvent;
+import org.springframework.cloud.sleuth.event.SpanStoppedEvent;
+import org.springframework.context.event.EventListener;
 
 import com.github.kristofa.brave.ServerTracer;
 
@@ -16,30 +14,25 @@ import com.github.kristofa.brave.ServerTracer;
  * @author Spencer Gibb
  */
 @CommonsLog
-public class ZipkinTrace extends DefaultTrace {
+public class ZipkinSpanListener {
 
 	private final ServerTracer serverTracer;
 
-	@Override
-	protected TraceScope doStart(final Span span) {
-		preTrace(span);
-		TraceScope scope = super.doStart(span);
-		scope.register(new Runnable() {
-			@Override
-			public void run() {
-				postTrace(span);
-			}
-		});
-		return scope;
-	}
-
-	public ZipkinTrace(ServerTracer serverTracer, Sampler<?> defaultSampler,
-			IdGenerator idGenerator, ApplicationEventPublisher publisher) {
-		super(defaultSampler, idGenerator, publisher);
+	public ZipkinSpanListener(ServerTracer serverTracer) {
 		this.serverTracer = serverTracer;
 	}
 
-	public void preTrace(Span context) {
+	@EventListener
+	public void start(SpanStartedEvent event) {
+		preTrace(event.getSpan());
+	}
+
+	@EventListener
+	public void start(SpanStoppedEvent event) {
+		postTrace(event.getSpan());
+	}
+
+	protected void preTrace(Span context) {
 		final TraceData traceData = getTraceData(context);
 		this.serverTracer.clearCurrentSpan();
 
@@ -79,7 +72,7 @@ public class ZipkinTrace extends DefaultTrace {
 		return context.getName();
 	}
 
-	public void postTrace(Span context) {
+	protected void postTrace(Span context) {
 		// We can submit this in any case. When server state is not set or
 		// we should not trace this request nothing will happen.
 		log.debug("Sending server send.");