Added device listener to fallback flow rule provider to trigger flow

entries probe after device events

Helpful for devices that do not provide configuration persistency,
to quickly restore flow rules after a reboot or an update.

Change-Id: I35dee1ff56076ddda7d22c353a01d518f2f88eed
(cherry picked from commit 0969e6f2)

@@ -24,6 +24,8 @@ import org.onosproject.core.ApplicationId;
 import org.onosproject.mastership.MastershipService;
 import org.onosproject.net.Device;
 import org.onosproject.net.DeviceId;
+import org.onosproject.net.device.DeviceEvent;
+import org.onosproject.net.device.DeviceListener;
 import org.onosproject.net.device.DeviceService;
 import org.onosproject.net.flow.CompletedBatchOperation;
 import org.onosproject.net.flow.FlowRule;
@@ -45,6 +47,7 @@ import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
 
 import static com.google.common.collect.ImmutableSet.copyOf;
+import static org.onosproject.net.device.DeviceEvent.Type.*;
 import static org.onosproject.net.flow.FlowRuleBatchEntry.FlowRuleOperation.*;
 
 /**
@@ -62,6 +65,7 @@ class FlowRuleDriverProvider extends AbstractProvider implements FlowRuleProvide
     private DeviceService deviceService;
     private MastershipService mastershipService;
 
+    private InternalDeviceListener deviceListener = new InternalDeviceListener();
     private ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();
     private ScheduledFuture<?> poller = null;
 
@@ -87,6 +91,8 @@ class FlowRuleDriverProvider extends AbstractProvider implements FlowRuleProvide
         this.deviceService = deviceService;
         this.mastershipService = mastershipService;
 
+        deviceService.addListener(deviceListener);
+
         if (poller != null && !poller.isCancelled()) {
             poller.cancel(false);
         }
@@ -164,14 +170,33 @@ class FlowRuleDriverProvider extends AbstractProvider implements FlowRuleProvide
         }
     }
 
+    private void pollDeviceFlowEntries(Device device) {
+        providerService.pushFlowMetrics(device.id(), device.as(FlowRuleProgrammable.class).getFlowEntries());
+    }
 
     private void pollFlowEntries() {
         deviceService.getAvailableDevices().forEach(device -> {
             if (mastershipService.isLocalMaster(device.id()) && device.is(FlowRuleProgrammable.class)) {
-                providerService.pushFlowMetrics(device.id(),
-                                                device.as(FlowRuleProgrammable.class).getFlowEntries());
+                pollDeviceFlowEntries(device);
             }
         });
     }
 
+    private class InternalDeviceListener implements DeviceListener {
+
+        @Override
+        public void event(DeviceEvent event) {
+            executor.schedule(() -> pollDeviceFlowEntries(event.subject()), 0, TimeUnit.SECONDS);
+        }
+
+        @Override
+        public boolean isRelevant(DeviceEvent event) {
+            Device device = event.subject();
+            return mastershipService.isLocalMaster(device.id()) && device.is(FlowRuleProgrammable.class) &&
+                    (event.type() == DEVICE_ADDED ||
+                            event.type() == DEVICE_UPDATED ||
+                            (event.type() == DEVICE_AVAILABILITY_CHANGED && deviceService.isAvailable(device.id())));
+        }
+    }
+
 }