Populate the base hash with the container tag hash if the process tag propagation feature flag is enabled

Author: ygree

dd-trace-core/src/main/java/datadog/trace/core/datastreams/DefaultPathwayContext.java

@@ -7,6 +7,7 @@
 import com.datadoghq.sketch.ddsketch.encoding.ByteArrayInput;
 import com.datadoghq.sketch.ddsketch.encoding.GrowingByteArrayOutput;
 import com.datadoghq.sketch.ddsketch.encoding.VarEncodingHelper;
+import datadog.common.container.ContainerInfo;
 import datadog.context.propagation.CarrierVisitor;
 import datadog.trace.api.Config;
 import datadog.trace.api.ProcessTags;
@@ -280,6 +281,10 @@ public static long getBaseHash(WellKnownTags wellKnownTags) {
     CharSequence processTags = ProcessTags.getTagsForSerialization();
     if (processTags != null) {
       builder.append(processTags);
+      String containerTagsHash = ContainerInfo.get().getContainerTagsHash();
+      if (containerTagsHash != null && !containerTagsHash.isEmpty()) {
+        builder.append(containerTagsHash);
+      }
     }
     return FNV64Hash.generateHash(builder.toString(), FNV64Hash.Version.v1);
   }

dd-trace-core/src/test/groovy/datadog/trace/core/datastreams/DefaultPathwayContextTest.groovy

@@ -1,5 +1,6 @@
 package datadog.trace.core.datastreams
 
+import datadog.common.container.ContainerInfo
 import datadog.communication.ddagent.DDAgentFeaturesDiscovery
 import datadog.trace.api.Config
 import datadog.trace.api.DDTraceId
@@ -481,6 +482,32 @@ class DefaultPathwayContextTest extends DDCoreSpecification {
     ProcessTags.reset()
   }
 
+  def "ContainerTagsHash used in hash calculation when enabled propagateTagsEnabled=#propagateTagsEnabled"() {
+    when:
+    injectSysConfig(EXPERIMENTAL_PROPAGATE_PROCESS_TAGS_ENABLED, propagateTagsEnabled.toString())
+    ProcessTags.reset()
+    ProcessTags.addTag("000", "first")
+    def firstBaseHash = DefaultPathwayContext.getBaseHash(wellKnownTags)
+
+    then:
+    ContainerInfo.get().setContainerTagsHash("<test-container-tags-hash>")
+    def secondBaseHash = DefaultPathwayContext.getBaseHash(wellKnownTags)
+
+    expect:
+    if (propagateTagsEnabled) {
+      assert secondBaseHash != firstBaseHash
+    } else {
+      assert secondBaseHash == firstBaseHash
+    }
+
+    cleanup:
+    injectSysConfig(EXPERIMENTAL_PROPAGATE_PROCESS_TAGS_ENABLED, "false")
+    ProcessTags.reset()
+
+    where:
+    propagateTagsEnabled << [true, false]
+  }
+
   def "Check context extractor decorator behavior"() {
     given:
     def sink = Mock(Sink)