Add ability to provide default datadog tags, that will be added to each span

Author: voidcontext

natchez-extras-datadog/src/main/scala/com/ovoenergy/natchez/extras/datadog/Datadog.scala

@@ -9,7 +9,7 @@ import cats.syntax.functor._
 import com.ovoenergy.natchez.extras.datadog.DatadogSpan.SpanNames
 import fs2.Stream
 import io.circe.{Encoder, Printer}
-import natchez.{EntryPoint, Kernel, Span}
+import natchez.{EntryPoint, Kernel, Span, TraceValue}
 import org.http4s.Method.PUT
 import org.http4s.Uri.Path.unsafeFromString
 import org.http4s.circe.CirceInstances.builder
@@ -119,7 +119,8 @@ object Datadog {
     client: Client[F],
     service: String,
     resource: String,
-    agentHost: Uri = uri"http://localhost:8126"
+    agentHost: Uri = uri"http://localhost:8126",
+    meta: Map[String, TraceValue] = Map.empty
   ): Resource[F, EntryPoint[F]] =
     for {
       queue <- spanQueue
@@ -130,7 +131,7 @@ object Datadog {
         def root(name: String, options: Span.Options): Resource[F, Span[F]] =
           Resource
             .eval(SpanIdentifiers.create.flatMap(Ref.of[F, SpanIdentifiers]))
-            .flatMap(DatadogSpan.create(queue, names(name)))
+            .flatMap(DatadogSpan.create(queue, names(name), meta))
             .widen
 
         def continue(name: String, kernel: Kernel, options: Span.Options): Resource[F, Span[F]] =

natchez-extras-datadog/src/test/scala/com/ovoenergy/natchez/extras/datadog/DatadogTest.scala

@@ -7,7 +7,7 @@ import com.ovoenergy.natchez.extras.datadog.Datadog.entryPoint
 import com.ovoenergy.natchez.extras.datadog.DatadogTags.SpanType.{Cache, Db, Web}
 import com.ovoenergy.natchez.extras.datadog.DatadogTags.spanType
 import munit.CatsEffectSuite
-import natchez.EntryPoint
+import natchez.{EntryPoint, TraceValue}
 import org.http4s.Request
 import org.http4s.circe.CirceEntityDecoder._
 import org.http4s.syntax.literals._
@@ -21,8 +21,8 @@ import scala.concurrent.duration._
  */
 class DatadogTest extends CatsEffectSuite {
 
-  def run(f: EntryPoint[IO] => IO[Unit]): IO[List[Request[IO]]] =
-    TestClient[IO].flatMap(c => entryPoint(c.client, "test", "blah").use(f) >> c.requests)
+  def run(f: EntryPoint[IO] => IO[Unit], meta: Map[String, TraceValue] = Map.empty): IO[List[Request[IO]]] =
+    TestClient[IO].flatMap(c => entryPoint(c.client, "test", "blah", meta = meta).use(f) >> c.requests)
 
   test("Obtain the agent host from the parameter") {
     assertIO(
@@ -126,6 +126,21 @@ class DatadogTest extends CatsEffectSuite {
     }
   }
 
+  test("Allow you to provide default tags") {
+    for {
+      res <- run(
+        _.root("bar").use(_.span("subspan").use(_ => IO.unit)),
+        Map("defaultTag1" -> "some-value", "defaultTag2" -> "some-other-value")
+      )
+      spans <- res.flatTraverse(_.as[List[List[SubmittableSpan]]]).map(_.flatten)
+    } yield {
+      assertEquals(spans.head.meta.get("defaultTag1"), Some("some-value"))
+      assertEquals(spans.head.meta.get("defaultTag2"), Some("some-other-value"))
+      assertEquals(spans.tail.head.meta.get("defaultTag1"), Some("some-value"))
+      assertEquals(spans.tail.head.meta.get("defaultTag2"), Some("some-other-value"))
+    }
+  }
+
   test("Inherit metadata into subspans but only at the time of creation") {
     run(
       _.root("bar:res").use { root =>