From 281251ce9d7637e1105d3ef786c2e0666a8d10bc Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Thu, 17 Apr 2025 13:46:42 +0200
Subject: [PATCH] Add process tags to client stats payload

---
 .../common/metrics/SerializingMetricWriter.java  | 13 ++++++++++++-
 .../metrics/SerializingMetricWriterTest.groovy   | 16 ++++++++++++++--
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/dd-trace-core/src/main/java/datadog/trace/common/metrics/SerializingMetricWriter.java b/dd-trace-core/src/main/java/datadog/trace/common/metrics/SerializingMetricWriter.java
index ce0d9f1de68..485b3e90bbc 100644
--- a/dd-trace-core/src/main/java/datadog/trace/common/metrics/SerializingMetricWriter.java
+++ b/dd-trace-core/src/main/java/datadog/trace/common/metrics/SerializingMetricWriter.java
@@ -5,7 +5,9 @@
 import datadog.communication.serialization.GrowableBuffer;
 import datadog.communication.serialization.WritableFormatter;
 import datadog.communication.serialization.msgpack.MsgPackWriter;
+import datadog.trace.api.ProcessTags;
 import datadog.trace.api.WellKnownTags;
+import datadog.trace.bootstrap.instrumentation.api.UTF8BytesString;
 
 public final class SerializingMetricWriter implements MetricWriter {
 
@@ -28,6 +30,7 @@ public final class SerializingMetricWriter implements MetricWriter {
   private static final byte[] STATS = "Stats".getBytes(ISO_8859_1);
   private static final byte[] OK_SUMMARY = "OkSummary".getBytes(ISO_8859_1);
   private static final byte[] ERROR_SUMMARY = "ErrorSummary".getBytes(ISO_8859_1);
+  private static final byte[] PROCESS_TAGS = "ProcessTags".getBytes(ISO_8859_1);
 
   private final WellKnownTags wellKnownTags;
   private final WritableFormatter writer;
@@ -48,7 +51,9 @@ public SerializingMetricWriter(WellKnownTags wellKnownTags, Sink sink, int initi
 
   @Override
   public void startBucket(int metricCount, long start, long duration) {
-    writer.startMap(6);
+    final UTF8BytesString processTags = ProcessTags.getTagsForSerialization();
+    final boolean writeProcessTags = processTags != null;
+    writer.startMap(6 + (writeProcessTags ? 1 : 0));
 
     writer.writeUTF8(RUNTIME_ID);
     writer.writeUTF8(wellKnownTags.getRuntimeId());
@@ -65,7 +70,13 @@ public void startBucket(int metricCount, long start, long duration) {
     writer.writeUTF8(VERSION);
     writer.writeUTF8(wellKnownTags.getVersion());
 
+    if (writeProcessTags) {
+      writer.writeUTF8(PROCESS_TAGS);
+      writer.writeUTF8(processTags);
+    }
+
     writer.writeUTF8(STATS);
+
     writer.startArray(1);
 
     writer.startMap(3);
diff --git a/dd-trace-core/src/test/groovy/datadog/trace/common/metrics/SerializingMetricWriterTest.groovy b/dd-trace-core/src/test/groovy/datadog/trace/common/metrics/SerializingMetricWriterTest.groovy
index 5b6ce8bee3d..e1d6f8f24b9 100644
--- a/dd-trace-core/src/test/groovy/datadog/trace/common/metrics/SerializingMetricWriterTest.groovy
+++ b/dd-trace-core/src/test/groovy/datadog/trace/common/metrics/SerializingMetricWriterTest.groovy
@@ -1,5 +1,7 @@
 package datadog.trace.common.metrics
 
+import datadog.trace.api.Config
+import datadog.trace.api.ProcessTags
 import datadog.trace.api.WellKnownTags
 import datadog.trace.api.Pair
 import datadog.trace.test.util.DDSpecification
@@ -9,13 +11,18 @@ import org.msgpack.core.MessageUnpacker
 import java.nio.ByteBuffer
 import java.util.concurrent.atomic.AtomicLongArray
 
+import static datadog.trace.api.config.GeneralConfig.EXPERIMENTAL_COLLECT_PROCESS_TAGS_ENABLED
 import static java.util.concurrent.TimeUnit.MILLISECONDS
 import static java.util.concurrent.TimeUnit.SECONDS
 
 class SerializingMetricWriterTest extends DDSpecification {
 
-  def "should produce correct message #iterationIndex" () {
+  def "should produce correct message #iterationIndex with process tags enabled #withProcessTags" () {
     setup:
+    if (withProcessTags) {
+      injectSysConfig(EXPERIMENTAL_COLLECT_PROCESS_TAGS_ENABLED, "true")
+    }
+    ProcessTags.reset()
     long startTime = MILLISECONDS.toNanos(System.currentTimeMillis())
     long duration = SECONDS.toNanos(10)
     WellKnownTags wellKnownTags = new WellKnownTags("runtimeid", "hostname", "env", "service", "version","language")
@@ -43,6 +50,7 @@ class SerializingMetricWriterTest extends DDSpecification {
         Pair.of(new MetricKey("resource" + i, "service" + i, "operation" + i, "type", 0, false), new AggregateMetric().recordDurations(10, new AtomicLongArray(1L)))
       })
     ]
+    withProcessTags << [true, false]
   }
 
 
@@ -70,7 +78,7 @@ class SerializingMetricWriterTest extends DDSpecification {
     void accept(int messageCount, ByteBuffer buffer) {
       MessageUnpacker unpacker = MessagePack.newDefaultUnpacker(buffer)
       int mapSize = unpacker.unpackMapHeader()
-      assert mapSize == 6
+      assert mapSize == (6 + (Config.get().isExperimentalCollectProcessTagsEnabled() ? 1 : 0))
       assert unpacker.unpackString() == "RuntimeId"
       assert unpacker.unpackString() == wellKnownTags.getRuntimeId() as String
       assert unpacker.unpackString() == "Seq"
@@ -81,6 +89,10 @@ class SerializingMetricWriterTest extends DDSpecification {
       assert unpacker.unpackString() == wellKnownTags.getEnv() as String
       assert unpacker.unpackString() == "Version"
       assert unpacker.unpackString() == wellKnownTags.getVersion() as String
+      if (Config.get().isExperimentalCollectProcessTagsEnabled()) {
+        assert unpacker.unpackString() == "ProcessTags"
+        assert unpacker.unpackString() == ProcessTags.tagsForSerialization as String
+      }
       assert unpacker.unpackString() == "Stats"
       int outerLength = unpacker.unpackArrayHeader()
       assert outerLength == 1