Add runtime.jvm.gc.collection.count metric (#2616)

* Add runtime.jvm.gc.collection.count metric

* Fix format violation

* Rename gc.collection to gc.collection.time

* Another rename 😅

instrumentation/runtime-metrics/javaagent/src/test/groovy/io/opentelemetry/instrumentation/javaagent/runtimemetrics/RuntimeMetricsTest.groovy

@@ -16,7 +16,8 @@ class RuntimeMetricsTest extends AgentInstrumentationSpecification {
 
     then:
     conditions.eventually {
-      assert getMetrics().any { it.name == "runtime.jvm.gc.collection" }
+      assert getMetrics().any { it.name == "runtime.jvm.gc.time" }
+      assert getMetrics().any { it.name == "runtime.jvm.gc.count" }
       assert getMetrics().any { it.name == "runtime.jvm.memory.area" }
       assert getMetrics().any { it.name == "runtime.jvm.memory.pool" }
     }

instrumentation/runtime-metrics/library/src/main/java/io/opentelemetry/instrumentation/runtimemetrics/GarbageCollector.java

@@ -25,7 +25,8 @@ import java.util.List;
  * <p>Example metrics being exported:
  *
  * <pre>
- *   runtime.jvm.gc.collection{gc="PS1"} 6.7
+ *   runtime.jvm.gc.time{gc="PS1"} 6.7
+ *   runtime.jvm.gc.count{gc="PS1"} 1
  * </pre>
  */
 public final class GarbageCollector {
@@ -40,7 +41,7 @@ public final class GarbageCollector {
       labelSets.add(Labels.of(GC_LABEL_KEY, gc.getName()));
     }
     meter
-        .longSumObserverBuilder("runtime.jvm.gc.collection")
+        .longSumObserverBuilder("runtime.jvm.gc.time")
         .setDescription("Time spent in a given JVM garbage collector in milliseconds.")
         .setUnit("ms")
         .setUpdater(
@@ -51,6 +52,19 @@ public final class GarbageCollector {
               }
             })
         .build();
+    meter
+        .longSumObserverBuilder("runtime.jvm.gc.count")
+        .setDescription(
+            "The number of collections that have occurred for a given JVM garbage collector.")
+        .setUnit("collections")
+        .setUpdater(
+            resultLongObserver -> {
+              for (int i = 0; i < garbageCollectors.size(); i++) {
+                resultLongObserver.observe(
+                    garbageCollectors.get(i).getCollectionCount(), labelSets.get(i));
+              }
+            })
+        .build();
   }
 
   private GarbageCollector() {}

smoke-tests/src/test/groovy/io/opentelemetry/smoketest/SpringBootSmokeTest.groovy

@@ -62,7 +62,8 @@ class SpringBootSmokeTest extends SmokeTest {
 
     then: "JVM metrics are exported"
     def metrics = new MetricsInspector(waitForMetrics())
-    metrics.hasMetricsNamed("runtime.jvm.gc.collection")
+    metrics.hasMetricsNamed("runtime.jvm.gc.time")
+    metrics.hasMetricsNamed("runtime.jvm.gc.count")
     metrics.hasMetricsNamed("runtime.jvm.memory.area")
     metrics.hasMetricsNamed("runtime.jvm.memory.pool")