Added gc and threads metrics

Author: segabriel

benchmarks-api/src/main/java/io/scalecube/benchmarks/BenchmarksState.java

@@ -6,7 +6,9 @@
 import com.codahale.metrics.Histogram;
 import com.codahale.metrics.Meter;
 import com.codahale.metrics.Timer;
+import com.codahale.metrics.jvm.GarbageCollectorMetricSet;
 import com.codahale.metrics.jvm.MemoryUsageGaugeSet;
+import com.codahale.metrics.jvm.ThreadStatesGaugeSet;
 
 import reactor.core.Exceptions;
 import reactor.core.publisher.Flux;
@@ -118,7 +120,9 @@ public final void start() {
       throw new IllegalStateException("BenchmarksState beforeAll() failed: " + ex, ex);
     }
 
+    settings.registry().register(settings.taskName() + "-gc", new GarbageCollectorMetricSet());
     settings.registry().register(settings.taskName() + "-memory", new MemoryUsageGaugeSet());
+    settings.registry().register(settings.taskName() + "-threads", new ThreadStatesGaugeSet());
 
     if (settings.consoleReporterEnabled()) {
       consoleReporter.start(settings.reporterInterval().toMillis(), TimeUnit.MILLISECONDS);