allow for namespaced environment tags (#1101)

Author: ivantopo

core/kamon-core-tests/src/test/scala/kamon/util/EnvironmentTagsSpec.scala

@@ -33,6 +33,14 @@ class EnvironmentTagsSpec extends AnyWordSpec with Matchers {
       |  tags {
       |    env = staging
       |    region = asia-1
+      |
+      |    k8s.namespace.name = production
+      |
+      |    some {
+      |      tag {
+      |        inside = example
+      |      }
+      |    }
       |  }
       |}
     """.stripMargin
@@ -97,12 +105,17 @@ class EnvironmentTagsSpec extends AnyWordSpec with Matchers {
           |include-service = no
           |include-host = no
           |include-instance = no
-          |exclude = [ "region", "env" ]
+          |exclude = [ "region", "env", "k8s.namespace.name", "some.tag.inside" ]
         """.stripMargin)
 
       val tags = EnvironmentTags.from(testEnv, config)
       tags shouldBe empty
     }
+
+    "allow for nested tag names" in {
+      testEnv.tags("k8s.namespace.name") shouldBe "production"
+      testEnv.tags("some.tag.inside") shouldBe "example"
+    }
   }
 
   implicit def toMap(tags: TagSet): Map[String, String] = {

core/kamon-core/src/main/scala/kamon/status/Environment.scala

@@ -19,7 +19,6 @@ package status
 
 import java.net.InetAddress
 import java.util.concurrent.ThreadLocalRandom
-
 import com.typesafe.config.Config
 import kamon.tag.TagSet
 import kamon.util.HexCodec
@@ -64,14 +63,31 @@ object Environment {
     val environmentConfig = config.getConfig("kamon.environment")
     val service = environmentConfig.getString("service")
     val tagsConfig = environmentConfig.getConfig("tags")
-    val tags = TagSet.from(tagsConfig.topLevelKeys.map(tag => (tag -> tagsConfig.getString(tag))).toMap)
+    val tags = flattenedTags(tagsConfig)
 
     val host = readValueOrGenerate(environmentConfig.getString("host"), generateHostname())
     val instance = readValueOrGenerate(environmentConfig.getString("instance"), s"$service@$host")
 
     Environment(host, service, instance, _incarnation, tags)
   }
 
+  /**
+    * Flattens all the configuration keys in the configuration so that we can have namespaced tag names
+    * like `k8s.namespace.name` or nested configurations and they will still generate a flat `x.y.z=value`
+    * set of tags.
+    */
+  private def flattenedTags(tagsConfig: Config): TagSet = {
+    import scala.collection.JavaConverters._
+
+    TagSet.from(
+      tagsConfig.entrySet()
+        .iterator()
+        .asScala
+        .map { e => e.getKey -> e.getValue.unwrapped().toString }
+        .toMap
+    )
+  }
+
   private def generateHostname(): String = {
     try InetAddress.getLocalHost.getHostName() catch { case t: Throwable =>
       _logger.warn("Could not automatically resolve a host name for this instance, falling back to 'localhost'", t)