From d2db875a38c0d94915f4dbcefd869760e79a3dd9 Mon Sep 17 00:00:00 2001
From: Takayuki Takagi <takagi.takayuki.yuuki@gmail.com>
Date: Tue, 10 Oct 2023 16:29:41 +0900
Subject: [PATCH] Add Datadog specific error tags (#1228)

---
 .../kamon/datadog/DatadogSpanReporter.scala   | 10 ++++++++-
 .../datadog/DatadogSpanReporterSpec.scala     | 21 +++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/reporters/kamon-datadog/src/main/scala/kamon/datadog/DatadogSpanReporter.scala b/reporters/kamon-datadog/src/main/scala/kamon/datadog/DatadogSpanReporter.scala
index cdd013850..de07f31e9 100644
--- a/reporters/kamon-datadog/src/main/scala/kamon/datadog/DatadogSpanReporter.scala
+++ b/reporters/kamon-datadog/src/main/scala/kamon/datadog/DatadogSpanReporter.scala
@@ -25,6 +25,7 @@ import kamon.{ ClassLoading, Kamon }
 import kamon.datadog.DatadogSpanReporter.Configuration
 import kamon.module.{ ModuleFactory, SpanReporter }
 import kamon.tag.{ Lookups, Tag, TagSet }
+import kamon.trace.Span.TagKeys
 import kamon.util.{ EnvironmentTags, Filter }
 import org.slf4j.LoggerFactory
 
@@ -52,7 +53,14 @@ object KamonDataDogTranslatorDefault extends KamonDataDogTranslator {
     val start = from.getEpochNano
     val duration = Duration.between(from, span.to)
     val marks = span.marks.map { m => m.key -> m.instant.getEpochNano.toString }.toMap
-    val tags = (span.tags.all() ++ span.metricTags.all() ++ additionalTags.all()).map { t =>
+    val errorTags = if (span.hasError) {
+      val builder = TagSet.builder()
+      span.tags.get(Lookups.option(TagKeys.ErrorMessage)).foreach(msg => builder.add("error.msg", msg))
+      span.tags.get(Lookups.option(TagKeys.ErrorStacktrace)).foreach(st => builder.add("error.stack", st))
+      builder.build()
+    } else TagSet.Empty
+
+    val tags = (span.tags.all() ++ span.metricTags.all() ++ errorTags.all() ++ additionalTags.all()).map { t =>
       t.key -> Tag.unwrapValue(t).toString
     }
     val meta = (marks ++ tags).filterKeys(tagFilter.accept(_)).toMap
diff --git a/reporters/kamon-datadog/src/test/scala/kamon/datadog/DatadogSpanReporterSpec.scala b/reporters/kamon-datadog/src/test/scala/kamon/datadog/DatadogSpanReporterSpec.scala
index 896b68e46..2257fa0ae 100644
--- a/reporters/kamon-datadog/src/test/scala/kamon/datadog/DatadogSpanReporterSpec.scala
+++ b/reporters/kamon-datadog/src/test/scala/kamon/datadog/DatadogSpanReporterSpec.scala
@@ -90,6 +90,26 @@ trait TestData {
     "error" -> 1
   )
 
+  val spanWithErrorTags = span.copy(tags = TagSet.from(Map(
+    "error" -> true,
+    "error.type" -> "RuntimeException",
+    "error.message" -> "Error message",
+    "error.stacktrace" -> "Error stacktrace"
+  )), hasError = true)
+
+  val jsonWithErrorTags = json ++ Json.obj(
+    "meta" -> Json.obj(
+      "error" -> "true",
+      "env" -> "staging",
+      "error.type" -> "RuntimeException",
+      "error.message" -> "Error message",
+      "error.msg" -> "Error message",
+      "error.stacktrace" -> "Error stacktrace",
+      "error.stack" -> "Error stacktrace"
+    ),
+    "error" -> 1
+  )
+
   val spanWithTags = span.copy(metricTags =
     TagSet.from(
       Map(
@@ -152,6 +172,7 @@ trait TestData {
     "span with marks" -> (Seq(spanWithMarks), Json.arr(Json.arr(jsonWithMarks))),
     "span with meta and marks" -> (Seq(spanWithTagsAndMarks), Json.arr(Json.arr(jsonWithTagsAndMarks))),
     "span with error" -> (Seq(spanWithError), Json.arr(Json.arr(jsonWithError))),
+    "span with error tags" -> (Seq(spanWithErrorTags), Json.arr(Json.arr(jsonWithErrorTags))),
 
     "multiple spans with same trace" -> (Seq(span, spanWithTags), Json.arr(Json.arr(json, jsonWithTags)))
   // "multiple spans with two traces" -> (Seq(span, spanWithTags, otherTraceSpan, span), Json.arr(Json.arr(json, jsonWithTags, json), Json.arr(otherTraceJson)))