Limiting the span name size to 50 chars

without this exceptions can occur when the span name is big
with this we're truncating the name to 50 chars

fixes #530

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

@@ -107,6 +107,10 @@ was a span present in this thread then it would become the parent of that span.
 
 IMPORTANT: Always clean after you create a span! Don't forget to close a span if you want to send it to Zipkin.
 
+IMPORTANT: If your span contains a name greater than 50 chars, then that name will
+be truncated to 50 chars. Your names have to be explicit and concrete. Big names lead to
+latency issues and sometimes even thrown exceptions.
+
 === Continuing spans [[continuing-spans]]
 
 Sometimes you don't want to create a new span but you want to continue one. Example of such a

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/messaging/AbstractTraceChannelInterceptor.java

@@ -8,6 +8,7 @@ import org.springframework.cloud.sleuth.Span;
 import org.springframework.cloud.sleuth.SpanTextMap;
 import org.springframework.cloud.sleuth.TraceKeys;
 import org.springframework.cloud.sleuth.Tracer;
+import org.springframework.cloud.sleuth.util.SpanNameUtil;
 import org.springframework.integration.channel.AbstractMessageChannel;
 import org.springframework.integration.context.IntegrationObjectSupport;
 import org.springframework.messaging.MessageChannel;
@@ -93,7 +94,7 @@ abstract class AbstractTraceChannelInterceptor extends ChannelInterceptorAdapter
 	}
 
 	String getMessageChannelName(MessageChannel channel) {
-		return MESSAGE_COMPONENT + ":" + getChannelName(channel);
+		return SpanNameUtil.shorten(MESSAGE_COMPONENT + ":" + getChannelName(channel));
 	}
 
 }

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

@@ -25,6 +25,7 @@ import org.springframework.cloud.sleuth.instrument.web.HttpSpanInjector;
 import org.springframework.cloud.sleuth.Span;
 import org.springframework.cloud.sleuth.Tracer;
 import org.springframework.cloud.sleuth.instrument.web.HttpTraceKeysInjector;
+import org.springframework.cloud.sleuth.util.SpanNameUtil;
 import org.springframework.http.HttpRequest;
 /**
  * Abstraction over classes that interact with Http requests. Allows you
@@ -54,7 +55,7 @@ abstract class AbstractTraceHttpRequestInterceptor {
 	 */
 	protected void publishStartEvent(HttpRequest request) {
 		URI uri = request.getURI();
-		String spanName = uriScheme(uri) + ":" + uri.getPath();
+		String spanName = getName(uri);
 		Span newSpan = this.tracer.createSpan(spanName);
 		this.spanInjector.inject(newSpan, new HttpRequestTextMap(request));
 		addRequestTags(request);
@@ -64,6 +65,10 @@ abstract class AbstractTraceHttpRequestInterceptor {
 		}
 	}
 
+	private String getName(URI uri) {
+		return SpanNameUtil.shorten(uriScheme(uri) + ":" + uri.getPath());
+	}
+
 	private String uriScheme(URI uri) {
 		return uri.getScheme() == null ? "http" : uri.getScheme();
 	}

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

@@ -30,6 +30,7 @@ import org.springframework.cloud.sleuth.Span;
 import org.springframework.cloud.sleuth.Tracer;
 import org.springframework.cloud.sleuth.instrument.web.HttpTraceKeysInjector;
 import org.springframework.cloud.sleuth.util.ExceptionUtils;
+import org.springframework.cloud.sleuth.util.SpanNameUtil;
 
 import feign.Client;
 import feign.Request;
@@ -101,7 +102,7 @@ class TraceFeignClient implements Client {
 
 	private String getSpanName(Request request) {
 		URI uri = URI.create(request.url());
-		return uriScheme(uri) + ":" + uri.getPath();
+		return SpanNameUtil.shorten(uriScheme(uri) + ":" + uri.getPath());
 	}
 
 	private String uriScheme(URI uri) {

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

@@ -29,6 +29,7 @@ import org.springframework.cloud.sleuth.instrument.async.SpanContinuingTraceCall
 import org.springframework.cloud.sleuth.instrument.async.SpanContinuingTraceRunnable;
 import org.springframework.cloud.sleuth.log.SpanLogger;
 import org.springframework.cloud.sleuth.util.ExceptionUtils;
+import org.springframework.cloud.sleuth.util.SpanNameUtil;
 
 /**
  * Default implementation of {@link Tracer}
@@ -38,6 +39,8 @@ import org.springframework.cloud.sleuth.util.ExceptionUtils;
  */
 public class DefaultTracer implements Tracer {
 
+	private static final int MAX_CHARS_IN_SPAN_NAME = 50;
+
 	private final Sampler defaultSampler;
 
 	private final Random random;
@@ -96,13 +99,14 @@ public class DefaultTracer implements Tracer {
 
 	@Override
 	public Span createSpan(String name, Sampler sampler) {
+		String shortenedName = SpanNameUtil.shorten(name);
 		Span span;
 		if (isTracing()) {
-			span = createChild(getCurrentSpan(), name);
+			span = createChild(getCurrentSpan(), shortenedName);
 		}
 		else {
 			long id = createId();
-			span = Span.builder().name(name)
+			span = Span.builder().name(shortenedName)
 					.traceIdHigh(this.traceId128 ? createId() : 0L)
 					.traceId(id)
 					.spanId(id).build();
@@ -115,6 +119,11 @@ public class DefaultTracer implements Tracer {
 		return continueSpan(span);
 	}
 
+	private String shortenNameIfNecessary(String name) {
+		int maxLength = name.length() > MAX_CHARS_IN_SPAN_NAME ? MAX_CHARS_IN_SPAN_NAME : name.length();
+		return name.substring(0, maxLength);
+	}
+
 	@Override
 	public Span detach(Span span) {
 		if (span == null) {
@@ -166,9 +175,10 @@ public class DefaultTracer implements Tracer {
 	}
 
 	Span createChild(Span parent, String name) {
+		String shortenedName = SpanNameUtil.shorten(name);
 		long id = createId();
 		if (parent == null) {
-			Span span = Span.builder().name(name)
+			Span span = Span.builder().name(shortenedName)
 					.traceIdHigh(this.traceId128 ? createId() : 0L)
 					.traceId(id)
 					.spanId(id).build();
@@ -180,7 +190,7 @@ public class DefaultTracer implements Tracer {
 			if (!isTracing()) {
 				SpanContextHolder.push(parent, true);
 			}
-			Span span = Span.builder().name(name)
+			Span span = Span.builder().name(shortenedName)
 					.traceIdHigh(parent.getTraceIdHigh())
 					.traceId(parent.getTraceId()).parent(parent.getSpanId()).spanId(id)
 					.processId(parent.getProcessId()).savedSpan(parent)

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

@@ -16,6 +16,8 @@
 
 package org.springframework.cloud.sleuth.util;
 
+import org.springframework.util.StringUtils;
+
 /**
  * Utility class that provides the name in hyphen based notation
  *
@@ -24,6 +26,16 @@ package org.springframework.cloud.sleuth.util;
  */
 public final class SpanNameUtil {
 
+	static final int MAX_NAME_LENGTH = 50;
+
+	public static String shorten(String name) {
+		if (StringUtils.isEmpty(name)) {
+			return name;
+		}
+		int maxLength = name.length() > MAX_NAME_LENGTH ? MAX_NAME_LENGTH : name.length();
+		return name.substring(0, maxLength);
+	}
+
 	public static String toLowerHyphen(String name) {
 		StringBuilder result = new StringBuilder();
 		for (int i = 0; i < name.length(); i++) {
@@ -35,6 +47,6 @@ public final class SpanNameUtil {
 				result.append(c);
 			}
 		}
-		return result.toString();
+		return SpanNameUtil.shorten(result.toString());
 	}
 }

spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/instrument/messaging/TraceChannelInterceptorTests.java

@@ -277,6 +277,28 @@ public class TraceChannelInterceptorTests implements MessageHandler {
 		then(TestSpanContextHolder.getCurrentSpan()).isNull();
 	}
 
+	@Test
+	public void shouldShortenTheNameWhenItsTooLarge() {
+		this.tracedChannel.send(MessageBuilder.withPayload("hi")
+				.setHeader(TraceMessageHeaders.SPAN_NAME_NAME, bigName())
+				.setHeader(TraceMessageHeaders.TRACE_ID_NAME, Span.idToHex(10L))
+				.setHeader(TraceMessageHeaders.SPAN_ID_NAME, Span.idToHex(20L)).build());
+
+		then(this.message).isNotNull();
+
+		then(this.accumulator.getSpans()).isNotEmpty();
+		this.accumulator.getSpans().forEach(span1 -> then(span1.getName().length()).isLessThanOrEqualTo(50));
+		then(TestSpanContextHolder.getCurrentSpan()).isNull();
+	}
+
+	private String bigName() {
+		StringBuilder sb = new StringBuilder();
+		for (int i = 0; i < 60; i++) {
+			sb.append("a");
+		}
+		return sb.toString();
+	}
+
 	@Test
 	public void serializeMutableHeaders() throws Exception {
 		Map<String, Object> headers = new HashMap<>();

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

@@ -36,6 +36,7 @@ import org.springframework.cloud.sleuth.sampler.AlwaysSampler;
 import org.springframework.cloud.sleuth.trace.DefaultTracer;
 import org.springframework.cloud.sleuth.trace.TestSpanContextHolder;
 import org.springframework.cloud.sleuth.util.ArrayListSpanAccumulator;
+import org.springframework.cloud.sleuth.util.ExceptionUtils;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.client.ClientHttpRequestInterceptor;
 import org.springframework.test.web.client.MockMvcClientHttpRequestFactory;
@@ -153,6 +154,28 @@ public class TraceRestTemplateInterceptorTests {
 		then(this.testController.span).hasNameEqualTo("http:/");
 	}
 
+	@Test
+	public void willShortenTheNameOfTheSpan() {
+		this.tracer.continueSpan(Span.builder().traceId(1L).spanId(2L).exportable(false).build());
+
+		try {
+			this.template.getForEntity("/" + bigName(), Map.class).getBody();
+		} catch (Exception e) {
+
+		}
+
+		then(this.spanAccumulator.getSpans().get(0).getName()).hasSize(50);
+		then(ExceptionUtils.getLastException()).isNull();
+	}
+
+	private String bigName() {
+		StringBuilder sb = new StringBuilder();
+		for (int i = 0; i < 60; i++) {
+			sb.append("a");
+		}
+		return sb.toString();
+	}
+
 	@RestController
 	public class TestController {
 

spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/instrument/web/client/feign/TraceFeignClientTests.java

@@ -105,4 +105,21 @@ public class TraceFeignClientTests {
 				.hasATag(Span.SPAN_ERROR_TAG_NAME, "exception has occurred");
 	}
 
+	@Test
+	public void should_shorten_the_span_name() throws IOException {
+		this.traceFeignClient.execute(
+				Request.create("GET", "http://foo/" + bigName(), new HashMap<>(), "".getBytes(),
+						Charset.defaultCharset()), new Request.Options());
+
+		then(this.spanAccumulator.getSpans().get(0).getName()).hasSize(50);
+	}
+
+	private String bigName() {
+		StringBuilder sb = new StringBuilder();
+		for (int i = 0; i < 60; i++) {
+			sb.append("a");
+		}
+		return sb.toString();
+	}
+
 }

spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/trace/DefaultTracerTests.java

@@ -68,7 +68,6 @@ public class DefaultTracerTests {
 
 	@Test
 	public void tracingWorks() {
-
 		DefaultTracer tracer = new DefaultTracer(NeverSampler.INSTANCE, new Random(),
 				new DefaultSpanNamer(), this.spanLogger, this.spanReporter, new TraceKeys());
 
@@ -219,6 +218,35 @@ public class DefaultTracerTests {
 		then(parent).isEqualTo(continuedSpan);
 	}
 
+	@Test
+	public void shouldCreateNewSpanWithShortenedName() {
+		DefaultTracer tracer = new DefaultTracer(new AlwaysSampler(), new Random(),
+				this.spanNamer, this.spanLogger, this.spanReporter, new TraceKeys());
+		Span span = tracer.createSpan(bigName());
+
+		then(span.getName().length()).isEqualTo(50);
+		tracer.close(span);
+	}
+
+	@Test
+	public void shouldCreateChildOfSpanWithShortenedName() {
+		DefaultTracer tracer = new DefaultTracer(new AlwaysSampler(), new Random(),
+				this.spanNamer, this.spanLogger, this.spanReporter, new TraceKeys());
+		Span span = Span.builder().name(bigName()).traceId(1L).spanId(1L).build();
+
+		Span child = tracer.createChild(span, bigName());
+
+		then(child.getName().length()).isEqualTo(50);
+	}
+
+	private String bigName() {
+		StringBuilder sb = new StringBuilder();
+		for (int i = 0; i < 60; i++) {
+			sb.append("a");
+		}
+		return sb.toString();
+	}
+
 	private Span assertSpan(List<Span> spans, Long parentId, String name) {
 		List<Span> found = findSpans(spans, parentId);
 		assertThat(found).as("More than one span with parentId %s", parentId).hasSize(1);

spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/util/SpanNameUtilTests.java

@@ -32,4 +32,25 @@ public class SpanNameUtilTests {
 		SleuthAssertions.then(SpanNameUtil.toLowerHyphen("MySuperClassName"))
 				.isEqualTo("my-super-class-name");
 	}
+
+	@Test
+	public void should_not_shorten_a_name_that_is_below_max_threshold() throws Exception {
+		SleuthAssertions.then(SpanNameUtil.shorten("someName"))
+				.isEqualTo("someName");
+	}
+
+	@Test
+	public void should_not_shorten_a_name_that_is_null() throws Exception {
+		SleuthAssertions.then(SpanNameUtil.shorten(null)).isNull();
+	}
+
+	@Test
+	public void should_shorten_a_name_that_is_above_max_threshold() throws Exception {
+		StringBuilder sb = new StringBuilder();
+		for (int i = 0; i < 60; i++) {
+			sb.append("a");
+		}
+		SleuthAssertions.then(SpanNameUtil.shorten(sb.toString()).length())
+				.isEqualTo(SpanNameUtil.MAX_NAME_LENGTH);
+	}
 }