Added docs on how to provide custom serviceName

without this entry in the docs people got confused on how to do this.

fixes #346

benchmarks/pom.xml

@@ -103,7 +103,7 @@
 		<dependency>
 			<groupId>org.assertj</groupId>
 			<artifactId>assertj-core</artifactId>
-			<version>2.1.0</version>
+			<version>3.5.2</version>
 			<scope>compile</scope>
 		</dependency>
 		<dependency>

docs/src/main/asciidoc/spring-cloud-sleuth.adoc

@@ -272,6 +272,19 @@ And you could register them like this:
 include::../../../..//spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/instrument/web/TraceFilterCustomExtractorTests.java[tags=configuration,indent=0]
 ----
 
+=== Custom SA tag in Zipkin
+
+Sometimes you want to create a manual Span that will wrap a call to an external service which is not instrumented.
+What you can do is to create a span with the `peer.service` tag that will contain a value of the service that you want to call.
+Below you can see an example of a call to Redis that is wrapped in such a span.
+
+[source,java]
+----
+include::../../../..//spring-cloud-sleuth-zipkin/src/test/java/org/springframework/cloud/sleuth/zipkin/HttpZipkinSpanReporterTest.java[tags=service_name,indent=0]
+----
+
+IMPORTANT: Remember not to add both `peer.service` tag and the `SA` tag! You have to add only `peer.service`.
+
 == Span Data as Messages
 
 You can accumulate and send span data over

pom.xml

@@ -195,7 +195,7 @@
 			<dependency>
 				<groupId>org.assertj</groupId>
 				<artifactId>assertj-core</artifactId>
-				<version>3.5.1</version>
+				<version>3.5.2</version>
 				<scope>test</scope>
 			</dependency>
 		</dependencies>

spring-cloud-sleuth-zipkin/src/test/java/org/springframework/cloud/sleuth/zipkin/HttpZipkinSpanReporterTest.java

@@ -1,16 +1,27 @@
 package org.springframework.cloud.sleuth.zipkin;
 
+import java.util.Random;
+import java.util.concurrent.atomic.AtomicReference;
+
 import org.junit.Rule;
 import org.junit.Test;
+import org.springframework.boot.autoconfigure.web.ServerProperties;
+import org.springframework.cloud.sleuth.DefaultSpanNamer;
+import org.springframework.cloud.sleuth.Tracer;
+import org.springframework.cloud.sleuth.log.NoOpSpanLogger;
 import org.springframework.cloud.sleuth.metric.CounterServiceBasedSpanMetricReporter;
 import org.springframework.cloud.sleuth.metric.SpanMetricReporter;
-import zipkin.Span;
+import org.springframework.cloud.sleuth.sampler.AlwaysSampler;
+import org.springframework.cloud.sleuth.trace.DefaultTracer;
+import org.springframework.cloud.sleuth.util.ExceptionUtils;
 
+import zipkin.Span;
 import zipkin.junit.HttpFailure;
 import zipkin.junit.ZipkinRule;
 
 import static java.util.Arrays.asList;
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.BDDAssertions.then;
 
 public class HttpZipkinSpanReporterTest {
 
@@ -113,6 +124,36 @@ public class HttpZipkinSpanReporterTest {
 		assertThat(this.inMemorySpanCounter.getDroppedSpans()).isEqualTo(2);
 	}
 
+	@Test
+	public void should_change_the_service_name_in_zipkin_to_the_manually_provided_one() {
+		AtomicReference<Span> receivedSpan = new AtomicReference<>();
+		Tracer tracer = new DefaultTracer(new AlwaysSampler(), new Random(), new DefaultSpanNamer(),
+				new NoOpSpanLogger(), new ZipkinSpanListener(receivedSpan::set,
+				new ServerPropertiesEndpointLocator(new ServerProperties(), "foo")));
+		// tag::service_name[]
+		org.springframework.cloud.sleuth.Span newSpan = tracer.createSpan("redis");
+		try {
+			newSpan.tag("redis.op", "get");
+			newSpan.tag("lc", "redis");
+			newSpan.logEvent(org.springframework.cloud.sleuth.Span.CLIENT_SEND);
+			// call redis service e.g
+			// return (SomeObj) redisTemplate.opsForHash().get("MYHASH", someObjKey);
+		} finally {
+			newSpan.tag("peer.service", "redisService");
+			newSpan.tag("peer.ipv4", "1.2.3.4");
+			newSpan.tag("peer.port", "1234");
+			newSpan.logEvent(org.springframework.cloud.sleuth.Span.CLIENT_RECV);
+			tracer.close(newSpan);
+		}
+		// end::service_name[]
+
+		then(tracer.getCurrentSpan()).isNull();
+		then(ExceptionUtils.getLastException()).isNull();
+		then(receivedSpan.get().binaryAnnotations)
+				.flatExtracting(input -> input.key, input -> new String(input.value))
+				.contains("peer.service", "redisService");
+	}
+
 	static Span span(long traceId, String spanName) {
 		return Span.builder().traceId(traceId).id(traceId).name(spanName).build();
 	}