ONOS-2043: Move device event handling in PacketManager off of event loop thread

Change-Id: Ia8b12e6ec3e732f0311adc7b3e7e63d07ad117e0

@@ -58,9 +58,12 @@ import org.slf4j.Logger;
 
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 import static org.slf4j.LoggerFactory.getLogger;
+import static org.onlab.util.Tools.groupedThreads;
 import static org.onosproject.security.AppGuard.checkPermission;
 
 
@@ -92,6 +95,8 @@ public class PacketManager
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     private FlowObjectiveService objectiveService;
 
+    private ExecutorService eventHandlingExecutor;
+
     private final DeviceListener deviceListener = new InternalDeviceListener();
 
     private final Map<Integer, PacketProcessor> processors = new ConcurrentHashMap<>();
@@ -100,6 +105,8 @@ public class PacketManager
 
     @Activate
     public void activate() {
+        eventHandlingExecutor = Executors.newSingleThreadExecutor(
+                        groupedThreads("onos/net/packet", "event-handler"));
         appId = coreService.getAppId(CoreService.CORE_APP_NAME);
         store.setDelegate(delegate);
         deviceService.addListener(deviceListener);
@@ -111,6 +118,7 @@ public class PacketManager
     public void deactivate() {
         store.unsetDelegate(delegate);
         deviceService.removeListener(deviceListener);
+        eventHandlingExecutor.shutdown();
         log.info("Stopped");
     }
 
@@ -277,6 +285,8 @@ public class PacketManager
     private class InternalDeviceListener implements DeviceListener {
         @Override
         public void event(DeviceEvent event) {
+            eventHandlingExecutor.execute(() -> {
+                try {
                     Device device = event.subject();
                     switch (event.type()) {
                     case DEVICE_ADDED:
@@ -290,6 +300,10 @@ public class PacketManager
                     default:
                         break;
                     }
+                } catch (Exception e) {
+                    log.warn("Failed to process {}", event, e);
+                }
+            });
         }
     }