Refactoring and cleanup in the Metrics module:

 * Removed logging related code inside class MetricsManager
 * Removed @Component related code, because it is not suppose to be used
   as an component.
 * Added a new class-wrapper so the Metrics can be used as a loadable service:
   MetricsManagerComponent. The name and the location of this class
   will be refactored in the future.
 * Added new method MetricsManager.removeMetric()
 * Line formatting
 * Changed "interface MetricsService" to public

@@ -68,7 +68,6 @@ private static Logger log = LoggerFactory.getLogger(SimpleNettyClient.class);
         metrics = new MetricsManager();
         Endpoint endpoint = new Endpoint(host, port);
         messaging.activate();
-        metrics.activate();
         MetricsFeature feature = new MetricsFeature("latency");
         MetricsComponent component = metrics.registerComponent("NettyMessaging");
         log.info("connecting " + host + ":" + port + " warmup:" + warmup + " iterations:" + iterations);
@@ -117,7 +116,6 @@ private static Logger log = LoggerFactory.getLogger(SimpleNettyClient.class);
     public static void stop() {
         try {
             messaging.deactivate();
-            metrics.deactivate();
         } catch (Exception e) {
             log.info("Unable to stop client %s", e);
         }

+package org.onlab.onos.impl;
+
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Deactivate;
+import org.apache.felix.scr.annotations.Service;
+
+import org.onlab.metrics.MetricsManager;
+
+/**
+ * Metrics service implementation.
+ */
+@Component(immediate = true)
+@Service
+public class MetricsManagerComponent extends MetricsManager {
+
+    @Activate
+    protected void activate() {
+        super.clear();
+    }
+
+    @Deactivate
+    protected void deactivate() {
+        super.clear();
+    }
+}

@@ -3,15 +3,7 @@ package org.onlab.metrics;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
-import java.util.concurrent.TimeUnit;
 
-import org.apache.felix.scr.annotations.Activate;
-import org.apache.felix.scr.annotations.Component;
-import org.apache.felix.scr.annotations.Deactivate;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import com.codahale.metrics.ConsoleReporter;
 import com.codahale.metrics.Counter;
 import com.codahale.metrics.Gauge;
 import com.codahale.metrics.Histogram;
@@ -53,48 +45,25 @@ import com.codahale.metrics.Timer;
  *   </code>
  * </pre>
  */
-@Component(immediate = true)
-public final class MetricsManager implements MetricsService {
+public class MetricsManager implements MetricsService {
 
-    private final Logger log = LoggerFactory.getLogger(getClass());
     /**
      * Registry to hold the Components defined in the system.
      */
-    private ConcurrentMap<String, MetricsComponent> componentsRegistry;
+    private ConcurrentMap<String, MetricsComponent> componentsRegistry =
+        new ConcurrentHashMap<>();
 
     /**
      * Registry for the Metrics objects created in the system.
      */
-    private final MetricRegistry metricsRegistry;
+    private MetricRegistry metricsRegistry = new MetricRegistry();
 
     /**
-     * Default Reporter for this metrics manager.
+     * Clears the internal state.
      */
-    //private final Slf4jReporter reporter;
-    private final ConsoleReporter reporter;
-
-    public MetricsManager() {
-        this.metricsRegistry = new MetricRegistry();
-//        this.reporter = Slf4jReporter.forRegistry(this.metricsRegistry)
-//                .outputTo(log)
-//                .convertRatesTo(TimeUnit.SECONDS)
-//                .convertDurationsTo(TimeUnit.MICROSECONDS)
-//                .build();
-        this.reporter = ConsoleReporter.forRegistry(this.metricsRegistry)
-                .convertRatesTo(TimeUnit.SECONDS)
-                .convertDurationsTo(TimeUnit.MICROSECONDS)
-                .build();
-    }
-
-    @Activate
-    public void activate() {
+    protected void clear() {
         this.componentsRegistry = new ConcurrentHashMap<>();
-        reporter.start(10, TimeUnit.SECONDS);
-    }
-
-    @Deactivate
-    public void deactivate() {
-        reporter.stop();
+        this.metricsRegistry = new MetricRegistry();
     }
 
     /**
@@ -107,7 +76,8 @@ public final class MetricsManager implements MetricsService {
     public MetricsComponent registerComponent(final String name) {
         MetricsComponent component = componentsRegistry.get(name);
         if (component == null) {
-            final MetricsComponent createdComponent = new MetricsComponent(name);
+            final MetricsComponent createdComponent =
+                new MetricsComponent(name);
             component = componentsRegistry.putIfAbsent(name, createdComponent);
             if (component == null) {
                 component = createdComponent;
@@ -221,6 +191,22 @@ public final class MetricsManager implements MetricsService {
     }
 
     /**
+     * Removes the metric with the given name.
+     *
+     * @param component component the Metric is defined in
+     * @param feature feature the Metric is defined in
+     * @param metricName local name of the metric
+     * @return true if the metric existed and was removed, otherwise false
+     */
+    @Override
+    public boolean removeMetric(final MetricsComponent component,
+                                final MetricsFeature feature,
+                                final String metricName) {
+        final String name = generateName(component, feature, metricName);
+        return metricsRegistry.remove(name);
+    }
+
+    /**
      * Fetches the existing Timers.
      *
      * @param filter filter to use to select Timers
@@ -272,8 +258,8 @@ public final class MetricsManager implements MetricsService {
      * Fetches the existing Histograms.
      *
      * @param filter filter to use to select Histograms
-     * @return a map of the Histograms that match the filter, with the key as the
-     *         name String to the Histogram.
+     * @return a map of the Histograms that match the filter, with the key as
+     *         the name String to the Histogram.
      */
     @Override
     public Map<String, Histogram> getHistograms(final MetricFilter filter) {
@@ -290,4 +276,3 @@ public final class MetricsManager implements MetricsService {
         metricsRegistry.removeMatching(filter);
     }
 }
-

@@ -13,7 +13,7 @@ import com.codahale.metrics.Timer;
 /**
  * Metrics Service to collect metrics.
  */
-interface MetricsService {
+public interface MetricsService {
 
     /**
      * Registers a component.
@@ -90,6 +90,18 @@ interface MetricsService {
              T metric);
 
     /**
+     * Removes the metric with the given name.
+     *
+     * @param component component the Metric is defined in
+     * @param feature feature the Metric is defined in
+     * @param metricName local name of the metric
+     * @return true if the metric existed and was removed, otherwise false
+     */
+    boolean removeMetric(MetricsComponent component,
+                         MetricsFeature feature,
+                         String metricName);
+
+    /**
      * Fetches the existing Timers.
      *
      * @param filter filter to use to select Timers
@@ -129,15 +141,15 @@ interface MetricsService {
      * Fetches the existing Histograms.
      *
      * @param filter filter to use to select Histograms
-     * @return a map of the Histograms that match the filter, with the key as the
-     *         name String to the Histogram.
+     * @return a map of the Histograms that match the filter, with the key as
+     *         the name String to the Histogram.
      */
      Map<String, Histogram> getHistograms(MetricFilter filter);
+
     /**
      * Removes all Metrics that match a given filter.
      *
      * @param filter filter to use to select the Metrics to remove.
      */
      void removeMatching(MetricFilter filter);
-
 }