From d64bbb1fdb634cafe13c0a19886550332d08f683 Mon Sep 17 00:00:00 2001
From: Ivan Topolnjak <ivantopo@gmail.com>
Date: Sat, 10 Feb 2018 01:12:36 +0100
Subject: add support for environment tags, fixes #510

---
 .../src/test/scala/kamon/EnvironmentSpec.scala      | 21 ++++++++++++++++++++-
 kamon-core/src/main/resources/reference.conf        | 12 ++++++++++++
 kamon-core/src/main/scala/kamon/Environment.scala   |  7 ++++---
 3 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/kamon-core-tests/src/test/scala/kamon/EnvironmentSpec.scala b/kamon-core-tests/src/test/scala/kamon/EnvironmentSpec.scala
index 82eed862..dadab5af 100644
--- a/kamon-core-tests/src/test/scala/kamon/EnvironmentSpec.scala
+++ b/kamon-core-tests/src/test/scala/kamon/EnvironmentSpec.scala
@@ -27,7 +27,7 @@ class EnvironmentSpec extends WordSpec with Matchers {
       |  instance = auto
       |}
     """.stripMargin
-  )
+  ).withFallback(ConfigFactory.defaultReference())
 
   "the Kamon environment" should {
     "assign a host and instance name when they are set to 'auto'" in {
@@ -36,6 +36,7 @@ class EnvironmentSpec extends WordSpec with Matchers {
       env.host shouldNot be("auto")
       env.instance shouldNot be("auto")
       env.instance shouldBe s"environment-spec@${env.host}"
+      env.tags shouldBe empty
     }
 
     "use the configured host and instance, if provided" in {
@@ -51,6 +52,24 @@ class EnvironmentSpec extends WordSpec with Matchers {
 
       env.host should be("spec-host")
       env.instance should be("spec-instance")
+      env.tags shouldBe empty
+    }
+
+    "read all environment tags, if provided" in {
+      val customConfig = ConfigFactory.parseString(
+        """
+          |kamon.environment.tags {
+          |  custom1 = "test1"
+          |  env = staging
+          |}
+        """.stripMargin)
+
+      val env = Environment.fromConfig(customConfig.withFallback(baseConfig))
+
+      env.tags should contain allOf(
+        ("custom1" -> "test1"),
+        ("env" -> "staging")
+      )
     }
 
     "always return the same incarnation name" in {
diff --git a/kamon-core/src/main/resources/reference.conf b/kamon-core/src/main/resources/reference.conf
index 659114ca..b3fd3b17 100644
--- a/kamon-core/src/main/resources/reference.conf
+++ b/kamon-core/src/main/resources/reference.conf
@@ -11,6 +11,18 @@ kamon {
 
     # Identifier for a particular instance of this service. If set to `auto` Kamon will use the pattern service@host.
     instance = "auto"
+
+    # Arbitraty key-value pairs that further identify the environment where this service instance is running. Typically
+    # these tags will be used by the reporting modules as additional tags for all metrics or spans. Take a look at each
+    # reporter module's configuration to ensure these tags are supported and included in the reported data. Example:
+    #
+    # kamon.environment.tags {
+    #   env = "staging"
+    #   region = "us-east-1"
+    # }
+    tags {
+
+    }
   }
 
   # FQCN of the reporter instances that should be loaded when calling `Kamon.reporters.loadReportersFromConfig()`. All
diff --git a/kamon-core/src/main/scala/kamon/Environment.scala b/kamon-core/src/main/scala/kamon/Environment.scala
index 80833352..1c00679d 100644
--- a/kamon-core/src/main/scala/kamon/Environment.scala
+++ b/kamon-core/src/main/scala/kamon/Environment.scala
@@ -21,15 +21,16 @@ import java.util.concurrent.ThreadLocalRandom
 import com.typesafe.config.Config
 import kamon.util.HexCodec
 
-case class Environment(host: String, service: String, instance: String, incarnation: String)
+case class Environment(host: String, service: String, instance: String, incarnation: String, tags: Map[String, String])
 
 object Environment {
   private val incarnation = HexCodec.toLowerHex(ThreadLocalRandom.current().nextLong())
 
   def fromConfig(config: Config): Environment = {
     val environmentConfig = config.getConfig("kamon.environment")
-
     val service = environmentConfig.getString("service")
+    val tagsConfig = environmentConfig.getConfig("tags")
+    val tags = tagsConfig.topLevelKeys.map(tag => (tag -> tagsConfig.getString(tag))).toMap
 
     val host = readValueOrGenerate(
       environmentConfig.getString("host"),
@@ -41,7 +42,7 @@ object Environment {
       s"$service@$host"
     )
 
-    Environment(host, service, instance, incarnation)
+    Environment(host, service, instance, incarnation, tags)
   }
 
   private def readValueOrGenerate(configuredValue: String, generator: => String): String =
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