adding group garbage collection functionality

If a group has a reference count of zero for more than
a configurable timeout, it is garbage collected.

This feature can be deactivated by component config.

Change-Id: I254d62a90ef7ac8d2ce2f406b67957455a5bf4d0

@@ -35,6 +35,7 @@ public class DefaultGroup extends DefaultGroupDescription
     private long bytes;
     private long referenceCount;
     private GroupId id;
+    private int age;
 
     /**
      * Initializes default values.
@@ -48,6 +49,7 @@ public class DefaultGroup extends DefaultGroupDescription
         packets = 0;
         bytes = 0;
         referenceCount = 0;
+        age = 0;
     }
 
     /**
@@ -128,6 +130,11 @@ public class DefaultGroup extends DefaultGroupDescription
         return this.bytes;
     }
 
+    @Override
+    public int age() {
+        return age;
+    }
+
     /**
      * Sets the new state for this entry.
      *
@@ -171,6 +178,11 @@ public class DefaultGroup extends DefaultGroupDescription
     @Override
     public void setReferenceCount(long referenceCount) {
         this.referenceCount = referenceCount;
+        if (referenceCount == 0) {
+            age++;
+        } else {
+            age = 0;
+        }
     }
 
     @Override
@@ -214,6 +226,7 @@ public class DefaultGroup extends DefaultGroupDescription
                 .add("description", super.toString())
                 .add("groupid", id)
                 .add("state", state)
+                .add("age", age)
                 .toString();
     }
 

@@ -96,4 +96,12 @@ public interface Group extends GroupDescription {
      * @return number of flow rules or other groups pointing to this group
      */
     long referenceCount();
+
+    /**
+     * Obtains the age of a group. The age reflects the number of polling rounds
+     * the group has had a reference count of zero.
+     *
+     * @return the age of the group as an integer
+     */
+    int age();
 }

@@ -23,6 +23,7 @@ import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 import org.onlab.junit.TestUtils;
+import org.onosproject.cfg.ComponentConfigAdapter;
 import org.onosproject.cluster.NodeId;
 import org.onosproject.core.DefaultGroupId;
 import org.onosproject.core.GroupId;
@@ -129,6 +130,7 @@ public class DistributedGroupStoreTest {
         groupStoreImpl.storageService = new TestStorageService();
         groupStoreImpl.clusterCommunicator = new ClusterCommunicationServiceAdapter();
         groupStoreImpl.mastershipService = new MasterOfAll();
+        groupStoreImpl.cfgService = new ComponentConfigAdapter();
         groupStoreImpl.activate();
         groupStore = groupStoreImpl;
         auditPendingReqQueue =

@@ -156,6 +156,11 @@ public class GroupsResourceTest extends ResourceTest {
         }
 
         @Override
+        public int age() {
+            return 0;
+        }
+
+        @Override
         public Type type() {
             return GroupDescription.Type.ALL;
         }