Add Span to Sampler method params

Also allows us to actually create a PercentageBasedSampler (I
don't think anyone tried it before) without resorting to
lazy beans and proxies.

Another freature added here is a default percentage sampler
if we know that spans need to be exported (zipkin or stream
is present).

Fixes gh-138

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

@@ -17,8 +17,11 @@
 package org.springframework.cloud.sleuth;
 
 /**
- * Extremely simple callback to determine the frequency that an action should be
+ * Extremely simple callback to determine the frequency that an action should be traced.
  */
 public interface Sampler {
-	boolean isSampled();
+	/**
+	 * @param span the current span (or null if there is none)
+	 */
+	boolean isSampled(Span span);
 }

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

@@ -17,13 +17,14 @@
 package org.springframework.cloud.sleuth.sampler;
 
 import org.springframework.cloud.sleuth.Sampler;
+import org.springframework.cloud.sleuth.Span;
 
 /**
  * @author Spencer Gibb
  */
 public class AlwaysSampler implements Sampler {
 	@Override
-	public boolean isSampled() {
+	public boolean isSampled(Span span) {
 		return true;
 	}
 }

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

@@ -17,6 +17,7 @@
 package org.springframework.cloud.sleuth.sampler;
 
 import org.springframework.cloud.sleuth.Sampler;
+import org.springframework.cloud.sleuth.Span;
 import org.springframework.cloud.sleuth.trace.SpanContextHolder;
 
 /**
@@ -27,7 +28,7 @@ public class IsTracingSampler implements Sampler {
 	public static IsTracingSampler INSTANCE = new IsTracingSampler();
 
 	@Override
-	public boolean isSampled() {
+	public boolean isSampled(Span span) {
 		return SpanContextHolder.isTracing();
 	}
 }

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

@@ -2,7 +2,6 @@ package org.springframework.cloud.sleuth.sampler;
 
 import org.springframework.cloud.sleuth.Sampler;
 import org.springframework.cloud.sleuth.Span;
-import org.springframework.cloud.sleuth.SpanAccessor;
 
 /**
  * Sampler that based on the given percentage rate will allow sampling.
@@ -23,16 +22,13 @@ import org.springframework.cloud.sleuth.SpanAccessor;
 public class PercentageBasedSampler implements Sampler {
 
 	private final SamplerConfiguration configuration;
-	private final SpanAccessor spanAccessor;
 
-	public PercentageBasedSampler(SamplerConfiguration configuration, SpanAccessor spanAccessor) {
+	public PercentageBasedSampler(SamplerConfiguration configuration) {
 		this.configuration = configuration;
-		this.spanAccessor = spanAccessor;
 	}
 
 	@Override
-	public boolean isSampled() {
-		Span currentSpan = this.spanAccessor.getCurrentSpan();
+	public boolean isSampled(Span currentSpan) {
 		long threshold = Math.abs(Long.MAX_VALUE * (int) (this.configuration.getPercentage() * 100)); // drops fractional percentage.
 		if (currentSpan == null || threshold == 0L) {
 			return false;

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

@@ -13,15 +13,9 @@ import lombok.Data;
 public class SamplerConfiguration {
 
 	/**
-	 * Percentage of requests that should be sampled.
-	 * E.g.
-	 * <ul>
-	 * <li> 1.0 - 100% requests should be sampled </li>
-	 * <li> 0.8 - 80% of requests should be sampled </li>
-	 * <li> 0.0 - 0% requests should be sampled </li>
-	 * </ul>
-	 *
-	 * The precision is whole-numbers only. We don't support 0.1% of the trace rate.
+	 * Percentage of requests that should be sampled. E.g. 1.0 - 100% requests should be
+	 * sampled. The precision is whole-numbers only (i.e. there's no support for 0.1% of
+	 * the traces).
 	 */
 	private float percentage = 0.1f;
 }

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

@@ -71,7 +71,7 @@ public class DefaultTracer implements Tracer {
 	@Override
 	public Span startTrace(String name, Sampler sampler) {
 		Span span;
-		if (isTracing() || sampler.isSampled()) {
+		if (isTracing() || sampler.isSampled(getCurrentSpan())) {
 			span = createChild(getCurrentSpan(), name);
 		}
 		else {

spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/instrument/web/TraceFilterTests.java

@@ -16,7 +16,16 @@
 
 package org.springframework.cloud.sleuth.instrument.web;
 
-import lombok.SneakyThrows;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.entry;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.mockito.MockitoAnnotations.initMocks;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+
+import java.util.Random;
+
 import org.junit.Before;
 import org.junit.Test;
 import org.mockito.Mock;
@@ -37,15 +46,7 @@ import org.springframework.mock.web.MockHttpServletResponse;
 import org.springframework.mock.web.MockServletContext;
 import org.springframework.test.web.servlet.request.MockHttpServletRequestBuilder;
 
-import java.util.Random;
-
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.entry;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertNull;
-import static org.mockito.MockitoAnnotations.initMocks;
-import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import lombok.SneakyThrows;
 
 /**
  * @author Spencer Gibb
@@ -216,8 +217,8 @@ public class TraceFilterTests {
 
 	private class DelegateSampler implements Sampler {
 		@Override
-		public boolean isSampled() {
-			return TraceFilterTests.this.sampler.isSampled();
+		public boolean isSampled(Span span) {
+			return TraceFilterTests.this.sampler.isSampled(span);
 		}
 	}
 }

spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/sampler/PercentageBasedSamplerTests.java

@@ -1,18 +1,18 @@
 package org.springframework.cloud.sleuth.sampler;
 
-import org.junit.Test;
-import org.springframework.cloud.sleuth.Span;
-import org.springframework.cloud.sleuth.SpanAccessor;
-
-import java.util.Random;
-
 import static org.assertj.core.api.BDDAssertions.then;
 import static org.assertj.core.data.Percentage.withPercentage;
 
+import java.util.Random;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.springframework.cloud.sleuth.Span;
+
 public class PercentageBasedSamplerTests {
 
 	SamplerConfiguration samplerConfiguration = new SamplerConfiguration();
-	SpanAccessor spanAccessor = traceReturningSpanWithUuid();
+	private Span span;
 	private static Random RANDOM = new Random();
 
 	@Test
@@ -20,17 +20,20 @@ public class PercentageBasedSamplerTests {
 		this.samplerConfiguration.setPercentage(1f);
 
 		for (int i = 0; i < 10; i++) {
-			then(new PercentageBasedSampler(this.samplerConfiguration, this.spanAccessor).isSampled()).isTrue();
+			then(new PercentageBasedSampler(this.samplerConfiguration).isSampled(this.span))
+					.isTrue();
 		}
 
 	}
 
 	@Test
-	public void should_reject_all_samples_when_config_has_0_percentage() throws Exception {
+	public void should_reject_all_samples_when_config_has_0_percentage()
+			throws Exception {
 		this.samplerConfiguration.setPercentage(0f);
 
 		for (int i = 0; i < 10; i++) {
-			then(new PercentageBasedSampler(this.samplerConfiguration, this.spanAccessor).isSampled()).isFalse();
+			then(new PercentageBasedSampler(this.samplerConfiguration).isSampled(this.span))
+					.isFalse();
 		}
 	}
 
@@ -42,30 +45,23 @@ public class PercentageBasedSamplerTests {
 
 		int numberOfSampledElements = countNumberOfSampledElements(numberOfIterations);
 
-		then(numberOfSampledElements).isCloseTo((int) (numberOfIterations * percentage), withPercentage(3));
+		then(numberOfSampledElements).isCloseTo((int) (numberOfIterations * percentage),
+				withPercentage(3));
 	}
 
 	private int countNumberOfSampledElements(int numberOfIterations) {
 		int passedCounter = 0;
 		for (int i = 0; i < numberOfIterations; i++) {
-			boolean passed = new PercentageBasedSampler(this.samplerConfiguration, traceReturningSpanWithUuid()).isSampled();
+			boolean passed = new PercentageBasedSampler(this.samplerConfiguration)
+					.isSampled(this.span);
 			passedCounter = passedCounter + (passed ? 1 : 0);
 		}
 		return passedCounter;
 	}
 
-	private SpanAccessor traceReturningSpanWithUuid() {
-		return new SpanAccessor() {
-			@Override
-			public Span getCurrentSpan() {
-				return Span.builder().traceId(RANDOM.nextLong()).build();
-			}
-
-			@Override
-			public boolean isTracing() {
-				return true;
-			}
-		};
+	@Before
+	public void setupSpan() {
+		this.span = Span.builder().traceId(RANDOM.nextLong()).build();
 	}
 
 }

spring-cloud-sleuth-samples/spring-cloud-sleuth-sample-messaging/src/main/java/sample/SampleMessagingApplication.java

@@ -20,8 +20,6 @@ import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
-import org.springframework.cloud.sleuth.Sampler;
-import org.springframework.cloud.sleuth.sampler.AlwaysSampler;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.EnableAspectJAutoProxy;
 import org.springframework.integration.annotation.IntegrationComponentScan;
@@ -48,11 +46,6 @@ public class SampleMessagingApplication {
 	@Autowired
 	private SampleRequestResponse transformer;
 
-	@Bean
-	public Sampler defaultSampler() {
-		return new AlwaysSampler();
-	}
-
 	@RequestMapping("/")
 	public String home() {
 		String msg = "Hello";

spring-cloud-sleuth-samples/spring-cloud-sleuth-sample-ribbon/src/main/java/sample/SampleRibbonApplication.java

@@ -20,8 +20,6 @@ import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.cloud.netflix.zuul.EnableZuulProxy;
-import org.springframework.cloud.sleuth.Sampler;
-import org.springframework.cloud.sleuth.sampler.AlwaysSampler;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.EnableAspectJAutoProxy;
 import org.springframework.scheduling.annotation.EnableAsync;
@@ -38,11 +36,6 @@ import com.github.kristofa.brave.SpanCollector;
 @EnableZuulProxy
 public class SampleRibbonApplication {
 
-	@Bean
-	public Sampler defaultSampler() {
-		return new AlwaysSampler();
-	}
-
 	public static void main(String[] args) {
 		SpringApplication.run(SampleRibbonApplication.class, args);
 	}

spring-cloud-sleuth-samples/spring-cloud-sleuth-sample-stream/src/main/java/sample/SampleSleuthApplication.java

@@ -18,8 +18,6 @@ package sample;
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
-import org.springframework.cloud.sleuth.Sampler;
-import org.springframework.cloud.sleuth.sampler.AlwaysSampler;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.EnableAspectJAutoProxy;
 import org.springframework.scheduling.annotation.EnableAsync;
@@ -34,11 +32,6 @@ public class SampleSleuthApplication {
 
 	public static final String CLIENT_NAME = "testApp";
 
-	@Bean
-	public Sampler defaultSampler() {
-		return new AlwaysSampler();
-	}
-
 	@Bean
 	public SampleController sampleController() {
 		return new SampleController();

spring-cloud-sleuth-samples/spring-cloud-sleuth-sample-zipkin/src/main/java/sample/SampleZipkinApplication.java

@@ -16,17 +16,16 @@
 
 package sample;
 
-import lombok.extern.slf4j.Slf4j;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
-import org.springframework.cloud.sleuth.Sampler;
-import org.springframework.cloud.sleuth.sampler.AlwaysSampler;
 import org.springframework.cloud.sleuth.zipkin.ZipkinSpanReporter;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.EnableAspectJAutoProxy;
 import org.springframework.scheduling.annotation.EnableAsync;
 
+import lombok.extern.slf4j.Slf4j;
+
 /**
  * @author Spencer Gibb
  */
@@ -36,14 +35,6 @@ import org.springframework.scheduling.annotation.EnableAsync;
 @Slf4j
 public class SampleZipkinApplication {
 
-	/**
-	 * Sleuth will not report trace data unless you define a sampler like below.
-	 */
-	@Bean
-	public Sampler defaultSampler() {
-		return new AlwaysSampler();
-	}
-
 	public static void main(String[] args) {
 		SpringApplication.run(SampleZipkinApplication.class, args);
 	}

spring-cloud-sleuth-samples/spring-cloud-sleuth-sample-zipkin/src/main/resources/application.yml

@@ -12,4 +12,4 @@ spring:
 sample:
   zipkin:
     # When enabled=false, traces log to the console. Comment to send to zipkin
-    enabled: true
+    enabled: false

spring-cloud-sleuth-stream/src/main/java/org/springframework/cloud/sleuth/stream/SleuthStreamAutoConfiguration.java

@@ -20,13 +20,17 @@ import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.autoconfigure.AutoConfigureBefore;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.boot.autoconfigure.web.ServerProperties;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.cloud.client.discovery.DiscoveryClient;
+import org.springframework.cloud.sleuth.Sampler;
 import org.springframework.cloud.sleuth.Span;
 import org.springframework.cloud.sleuth.metric.SpanReporterService;
+import org.springframework.cloud.sleuth.sampler.PercentageBasedSampler;
+import org.springframework.cloud.sleuth.sampler.SamplerConfiguration;
 import org.springframework.cloud.stream.annotation.EnableBinding;
 import org.springframework.cloud.stream.config.ChannelBindingAutoConfiguration;
 import org.springframework.context.annotation.Bean;
@@ -48,12 +52,18 @@ import org.springframework.messaging.support.ChannelInterceptorAdapter;
  * @author Dave Syer
  */
 @Configuration
-@EnableConfigurationProperties(SleuthStreamProperties.class)
+@EnableConfigurationProperties({SleuthStreamProperties.class, SamplerConfiguration.class})
 @AutoConfigureBefore(ChannelBindingAutoConfiguration.class)
 @EnableBinding(SleuthSource.class)
 @ConditionalOnProperty(value = "spring.sleuth.stream.enabled", matchIfMissing = true)
 public class SleuthStreamAutoConfiguration {
 
+	@Bean
+	@ConditionalOnMissingBean
+	public Sampler defaultTraceSampler(SamplerConfiguration config) {
+		return new PercentageBasedSampler(config);
+	}
+
 	@Bean
 	@GlobalChannelInterceptor(patterns = SleuthSource.OUTPUT, order = Ordered.HIGHEST_PRECEDENCE)
 	public ChannelInterceptor zipkinChannelInterceptor(final SpanReporterService spanReporterService) {

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

@@ -18,6 +18,7 @@ package org.springframework.cloud.sleuth.zipkin;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.autoconfigure.AutoConfigureBefore;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
@@ -25,7 +26,11 @@ import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.boot.autoconfigure.web.ServerProperties;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.cloud.client.discovery.DiscoveryClient;
+import org.springframework.cloud.sleuth.Sampler;
+import org.springframework.cloud.sleuth.autoconfig.TraceAutoConfiguration;
 import org.springframework.cloud.sleuth.metric.SpanReporterService;
+import org.springframework.cloud.sleuth.sampler.PercentageBasedSampler;
+import org.springframework.cloud.sleuth.sampler.SamplerConfiguration;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 
@@ -34,21 +39,22 @@ import org.springframework.context.annotation.Configuration;
  * @author Spencer Gibb
  */
 @Configuration
-@EnableConfigurationProperties
+@EnableConfigurationProperties({ZipkinProperties.class, SamplerConfiguration.class})
 @ConditionalOnProperty(value = "spring.zipkin.enabled", matchIfMissing = true)
+@AutoConfigureBefore(TraceAutoConfiguration.class)
 public class ZipkinAutoConfiguration {
 
 	@Bean
 	@ConditionalOnMissingBean(ZipkinSpanReporter.class)
-	public ZipkinSpanReporter reporter(SpanReporterService spanReporterService) {
-		ZipkinProperties zipkin = zipkinProperties();
+	public ZipkinSpanReporter reporter(SpanReporterService spanReporterService, ZipkinProperties zipkin) {
 		return new HttpZipkinSpanReporter(zipkin.getBaseUrl(), zipkin.getFlushInterval(),
 				spanReporterService);
 	}
 
 	@Bean
-	public ZipkinProperties zipkinProperties() {
-		return new ZipkinProperties();
+	@ConditionalOnMissingBean
+	public Sampler defaultTraceSampler(SamplerConfiguration config) {
+		return new PercentageBasedSampler(config);
 	}
 
 	@Bean

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

@@ -26,8 +26,6 @@ import lombok.Data;
 @ConfigurationProperties("spring.zipkin")
 @Data
 public class ZipkinProperties {
-	// Sample rate = 1.0 means 100% of requests will get traced.
-	private float fixedSampleRate = 1.0f;
 	/** URL of the zipkin query server instance. */
 	private String baseUrl = "http://localhost:9411/";
 	private boolean enabled = true;