Add method to read service name from a span's service tag

Author: jeffbaker

reader/src/main/scala/com/expedia/www/haystack/trace/reader/readers/utils/SpanUtils.scala

@@ -44,6 +44,23 @@ object SpanUtils {
     containsLogTag(span, SERVER_RECV_EVENT) && containsLogTag(span, SERVER_SEND_EVENT)
   }
 
+  def getEffectiveServiceName(span: Span): String = {
+      if(containsServiceTag(span)) {
+        val serviceTagValue = span.getTagsList.asScala.find(_.getKey == SERVICE_TAG_KEY).map(_.getVStr).get
+        if(serviceTagValue == "") { // Span protobuf-generated code returns empty string for a missing tag key
+          span.getServiceName
+        } else {
+          serviceTagValue
+        }
+      } else {
+        span.getServiceName
+      }
+   }
+
+  def containsServiceTag(span: Span): Boolean = {
+    containsTag(span, SERVICE_TAG_KEY)
+  }
+
   def containsClientLogTag(span: Span): Boolean = {
     containsLogTag(span, CLIENT_RECV_EVENT) && containsLogTag(span, CLIENT_RECV_EVENT)
   }
@@ -92,6 +109,12 @@ object SpanUtils {
     })
   }
 
+  private def containsTag(span: Span, key: String) = {
+    span.getTagsList.asScala.exists(tag => {
+      tag.getKey.equalsIgnoreCase(key)
+    })
+  }
+
   def createAutoGeneratedRootSpan(spans: Seq[Span],
                                   reason: String,
                                   rootSpanId: String): Span.Builder = {
@@ -133,6 +156,7 @@ object SpanMarkers {
   val CLIENT_RECV_EVENT = "cr"
 
   val SPAN_KIND_TAG_KEY = "span.kind"
+  val SERVICE_TAG_KEY = "service"
   val SERVER_SPAN_KIND = "server"
   val CLIENT_SPAN_KIND = "client"
 }

reader/src/test/scala/com/expedia/www/haystack/trace/reader/readers/utils/SpanUtilsSpec.scala

@@ -0,0 +1,50 @@
+/*
+ *  Copyright 2018 Expedia, Inc.
+ *
+ *       Licensed under the Apache License, Version 2.0 (the "License");
+ *       you may not use this file except in compliance with the License.
+ *      You may obtain a copy of the License at
+ *
+ *           http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *       Unless required by applicable law or agreed to in writing, software
+ *       distributed under the License is distributed on an "AS IS" BASIS,
+ *       WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *       See the License for the specific language governing permissions and
+ *       limitations under the License.
+ */
+package com.expedia.www.haystack.trace.reader.readers.utils
+
+import java.lang.System.currentTimeMillis
+
+import com.expedia.open.tracing.Span
+import com.expedia.open.tracing.Tag
+import com.expedia.www.haystack.trace.reader.readers.utils.SpanMarkers.SERVICE_TAG_KEY
+import com.expedia.www.haystack.trace.reader.unit.BaseUnitTestSpec
+
+class SpanUtilsSpec extends BaseUnitTestSpec {
+  val ServiceNameInAttribute: String = currentTimeMillis + "ServiceNameInAttribute"
+  val ServiceNameInTag: String = currentTimeMillis + "ServiceNameInTag"
+
+  describe("SpanUtils object, getEffectiveServiceName() method") {
+    it("should return the span's service name if the 'service' tag is not found") {
+      val span = Span.newBuilder().setServiceName(ServiceNameInAttribute).build
+      val serviceName = SpanUtils.getEffectiveServiceName(span)
+      assert(serviceName == ServiceNameInAttribute)
+    }
+
+    it("should return the tag's service name if the 'service' tag has a non-null value") {
+      val tag = Tag.newBuilder().setKey(SERVICE_TAG_KEY).setVStr(ServiceNameInTag).build
+      val span = Span.newBuilder().setServiceName(ServiceNameInAttribute).addTags(tag).build
+      val serviceName = SpanUtils.getEffectiveServiceName(span)
+      assert(serviceName == ServiceNameInTag)
+    }
+
+    it("should return the span's service name if the 'service' tag has no value") {
+      val tag = Tag.newBuilder().setKey(SERVICE_TAG_KEY).build
+      val span = Span.newBuilder().setServiceName(ServiceNameInAttribute).addTags(tag).build
+      val serviceName = SpanUtils.getEffectiveServiceName(span)
+      assert(serviceName == ServiceNameInAttribute)
+    }
+  }
+}