Cluster metrics internal API and cluster-wide transport of metrics data.

* Create Cluster Metrics API
* Create transport of relevant metrics data
Does not include load-balancing routers.

akka-cluster/src/test/scala/akka/cluster/NodeMetricsSpec.scala

@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2009-2012 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package akka.cluster
+
+import akka.testkit.AkkaSpec
+import akka.actor.Address
+
+@org.junit.runner.RunWith(classOf[org.scalatest.junit.JUnitRunner])
+class NodeMetricsSpec extends AkkaSpec with AbstractClusterMetricsSpec with MetricSpec {
+
+  val collector = createMetricsCollector
+
+  val node1 = Address("akka", "sys", "a", 2554)
+
+  val node2 = Address("akka", "sys", "a", 2555)
+
+  "NodeMetrics must" must {
+    "recognize updatable nodes" in {
+      (NodeMetrics(node1, 0) updatable NodeMetrics(node1, 1)) must be(true)
+    }
+
+    "recognize non-updatable nodes" in {
+      (NodeMetrics(node1, 1) updatable NodeMetrics(node2, 0)) must be(false)
+    }
+
+    "return correct result for 2 'same' nodes" in {
+      (NodeMetrics(node1, 0) same NodeMetrics(node1, 0)) must be(true)
+    }
+
+    "return correct result for 2 not 'same' nodes" in {
+      (NodeMetrics(node1, 0) same NodeMetrics(node2, 0)) must be(false)
+    }
+
+    "merge 2 NodeMetrics by most recent" in {
+      val sample1 = NodeMetrics(node1, 1, collector.sample.metrics)
+      val sample2 = NodeMetrics(node1, 2, collector.sample.metrics)
+
+      val merged = sample1 merge sample2
+      merged.timestamp must be(sample2.timestamp)
+      merged.metrics must be(sample2.metrics)
+    }
+
+    "not merge 2 NodeMetrics if master is more recent" in {
+      val sample1 = NodeMetrics(node1, 1, collector.sample.metrics)
+      val sample2 = NodeMetrics(node2, 0, sample1.metrics)
+
+      val merged = sample2 merge sample2 // older and not same
+      merged.timestamp must be(sample2.timestamp)
+      merged.metrics must be(sample2.metrics)
+    }
+  }
+}
+