Fix split-by-tags for tags configured by OpenTelemetry name

dd-trace-core/src/main/java/datadog/trace/core/taginterceptor/TagInterceptor.java

@@ -27,6 +27,7 @@
 import datadog.trace.api.Config;
 import datadog.trace.api.ConfigDefaults;
 import datadog.trace.api.DDTags;
+import datadog.trace.api.KnownTagCodec;
 import datadog.trace.api.Pair;
 import datadog.trace.api.TagMap;
 import datadog.trace.api.config.GeneralConfig;
@@ -41,6 +42,7 @@
 import datadog.trace.bootstrap.instrumentation.api.UTF8BytesString;
 import datadog.trace.core.DDSpanContext;
 import java.net.URI;
+import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
 import javax.annotation.Nonnull;
@@ -77,9 +79,9 @@ public TagInterceptor(
       boolean jeeSplitByDeployment) {
     this.isServiceNameSetByUser = isServiceNameSetByUser;
     this.inferredServiceName = inferredServiceName;
-    this.splitServiceTags = splitServiceTags;
+    this.splitServiceTags = withCanonicalNames(splitServiceTags);
     this.ruleFlags = ruleFlags;
-    splitByServletContext = splitServiceTags.contains(SERVLET_CONTEXT);
+    splitByServletContext = this.splitServiceTags.contains(SERVLET_CONTEXT);
 
     shouldSet404ResourceName =
         ruleFlags.isEnabled(URL_AS_RESOURCE_NAME)
@@ -89,6 +91,25 @@ public TagInterceptor(
     this.jeeSplitByDeployment = jeeSplitByDeployment;
   }
 
+  /**
+   * Adds the Datadog name of each configured tag: entries set on the span builder arrive under it,
+   * so a tag configured by its OpenTelemetry name (e.g. {@code db.system}) would otherwise be
+   * missed.
+   */
+  private static Set<String> withCanonicalNames(Set<String> tags) {
+    Set<String> result = null;
+    for (String tag : tags) {
+      String canonical = KnownTagCodec.canonicalTagName(tag);
+      if (!canonical.equals(tag) && !tags.contains(canonical)) {
+        if (result == null) {
+          result = new HashSet<>(tags);
+        }
+        result.add(canonical);
+      }
+    }
+    return result == null ? tags : result;
+  }
+
   public boolean needsIntercept(TagMap map) {
     for (TagMap.EntryReader entry : map) {
       if (needsIntercept(entry.tag())) return true;

dd-trace-core/src/test/java/datadog/trace/core/taginterceptor/TagInterceptorTest.java

@@ -9,6 +9,7 @@
 import static datadog.trace.bootstrap.instrumentation.api.Tags.HTTP_STATUS;
 import static datadog.trace.bootstrap.instrumentation.api.Tags.HTTP_URL;
 import static datadog.trace.test.junit.utils.config.WithConfigExtension.injectSysConfig;
+import static java.util.Collections.emptyMap;
 import static java.util.Collections.emptySet;
 import static java.util.Collections.singletonMap;
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -48,8 +49,11 @@
 import datadog.trace.test.junit.utils.config.WithConfig;
 import datadog.trace.test.junit.utils.converter.ConfigDefaultsConverter;
 import datadog.trace.test.junit.utils.converter.TagsConverter;
+import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
 import java.util.function.Function;
 import java.util.stream.Stream;
 import org.junit.jupiter.api.Test;
@@ -190,15 +194,52 @@ void mappingCausesServletContextToNotChangeServiceName(String serviceName) {
     assertEquals("new-service", span.getServiceName());
   }
 
+  @TableTest({
+    "scenario                      | configured                  | tag          | expectedBuilder | expectedSetter",
+    "configured by OTel name       | db.system                   | db.system    | split           | split         ",
+    "configured by Datadog name    | db.type                     | db.type      | split           | split         ",
+    "Datadog config, OTel tag      | db.type                     | db.system    | split           | my-service    ",
+    "OTel config, Datadog tag      | db.system                   | db.type      | split           | split         ",
+    "custom tag                    | custom.tag                  | custom.tag   | split           | split         ",
+    "unconfigured tag              | db.system                   | other.tag    | my-service      | my-service    ",
+    "empty configuration           | ''                          | db.system    | my-service      | my-service    ",
+    "both names, OTel tag          | db.system,db.type           | db.system    | split           | split         ",
+    "both names, Datadog tag       | db.system,db.type           | db.type      | split           | split         ",
+    "custom tag survives expansion | db.system,custom.tag        | custom.tag   | split           | split         ",
+    "first of two renamed tags     | db.system,db.operation.name | db.type      | split           | split         ",
+    "second of two renamed tags    | db.system,db.operation.name | db.operation | split           | split         "
+  })
+  void splitByTagsMatchesCanonicalAndOriginalNames(
+      String configured, String tag, String expectedBuilder, String expectedSetter) {
+    Set<String> configuredTags =
+        configured.isEmpty() ? emptySet() : new HashSet<>(Arrays.asList(configured.split(",")));
+    CoreTracer tracer = createSplittingTracer(configuredTags, emptyMap());
+
+    AgentSpan builderSpan = tracer.buildSpan("datadog", "some span").withTag(tag, "split").start();
+    AgentSpan setterSpan = tracer.buildSpan("datadog", "some span").start();
+    setterSpan.setTag(tag, "split");
+
+    assertEquals(expectedBuilder, builderSpan.getServiceName());
+    assertEquals(expectedSetter, setterSpan.getServiceName());
+
+    CoreTracer defaultTagTracer = createSplittingTracer(configuredTags, singletonMap(tag, "split"));
+    AgentSpan defaultTagSpan = defaultTagTracer.buildSpan("datadog", "some span").start();
+
+    assertEquals(expectedBuilder, defaultTagSpan.getServiceName());
+  }
+
   private CoreTracer createSplittingTracer(String tag) {
+    return createSplittingTracer(Collections.singleton(tag), emptyMap());
+  }
+
+  private CoreTracer createSplittingTracer(Set<String> tags, Map<String, String> defaultSpanTags) {
     return tracerBuilder()
         .serviceName("my-service")
         .writer(new LoggingWriter())
         .sampler(new AllSampler())
-        // equivalent to split-by-tags: tag
-        .tagInterceptor(
-            new TagInterceptor(
-                true, "my-service", Collections.singleton(tag), new RuleFlags(), false))
+        .defaultSpanTags(defaultSpanTags)
+        // equivalent to split-by-tags: tags
+        .tagInterceptor(new TagInterceptor(true, "my-service", tags, new RuleFlags(), false))
         .build();
   }