From b068f55387e0cfe92b3ec403132d5c851d51eb00 Mon Sep 17 00:00:00 2001
From: Ivan Topolnjak <ivantopo@gmail.com>
Date: Wed, 14 Nov 2018 22:35:33 +0100
Subject: add a simple metric group utility for instrumentations

---
 .../scala/kamon/instrumentation/MetricGroup.scala  | 64 ++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 kamon-core/src/main/scala/kamon/instrumentation/MetricGroup.scala

(limited to 'kamon-core/src/main/scala/kamon/instrumentation/MetricGroup.scala')

diff --git a/kamon-core/src/main/scala/kamon/instrumentation/MetricGroup.scala b/kamon-core/src/main/scala/kamon/instrumentation/MetricGroup.scala
new file mode 100644
index 00000000..b27c6f54
--- /dev/null
+++ b/kamon-core/src/main/scala/kamon/instrumentation/MetricGroup.scala
@@ -0,0 +1,64 @@
+package kamon
+package instrumentation
+
+import kamon.metric.Metric
+import scala.collection.JavaConverters._
+
+/**
+  * Utility class that helps to apply the same tags to several metrics and keep track of all the tagged instruments so
+  * that they can later be cleaned up. This becomes specially handy when tracking several metrics that are related to
+  * each other and should be created and removed together, for example, when tracking metrics on a thread pool you will
+  * want to register several metrics related to one particular thread pool with a number of common tags and then remove
+  * all of those metrics once the thread pool is shut down.
+  *
+  * @param commonTags Tags to be applied to all metrics returned by calls to the tag method.
+  */
+abstract class MetricGroup(commonTags: Map[String, String]) {
+  private var _groupInstruments = List.empty[(Metric[_], Map[String, String])]
+
+  /**
+    * Tag a metric using the common tags.
+    */
+  def tag[T](metric: Metric[T]): T =
+    register(metric, commonTags)
+
+  /**
+    * Tag a metric using the supplied key/value pair and the common tags.
+    */
+  def tag[T](metric: Metric[T], key: String, value: String): T =
+    register(metric, commonTags ++ Map(key -> value))
+
+  /**
+    * Tag a metric using the supplied tuple and the common tags.
+    */
+  def tag[T](metric: Metric[T], tag: (String, String)): T =
+    register(metric, commonTags + tag)
+
+  /**
+    * Tag a metric using the supplied tags map and the common tags.
+    */
+  def tag[T](metric: Metric[T], tags: Map[String, String]): T =
+    register(metric, commonTags ++ tags)
+
+  /**
+    * Tag a metric using the supplied tags map and the common tags.
+    */
+  def tag[T](metric: Metric[T], tags: java.util.Map[String, String]): T =
+    register(metric, commonTags ++ tags.asScala.toMap)
+
+
+  private def register[T](metric: Metric[T], tags: Map[String, String]): T = synchronized {
+    _groupInstruments = (metric -> tags) :: _groupInstruments
+    metric.refine(tags)
+  }
+
+
+  /**
+    * Removes all metrics that were tagged by this group.
+    */
+  def cleanup(): Unit = synchronized {
+    _groupInstruments foreach {
+      case (metric, tags) => metric.remove(tags)
+    }
+  }
+}
\ No newline at end of file
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