ONOS-5182 Refactored SONA to cache network states

Change-Id: Ib316fa5fa5d36e9da370a1578ac55de4a8dd9b04
diff --git a/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/api/InstancePortEvent.java b/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/api/InstancePortEvent.java
new file mode 100644
index 0000000..945772e
--- /dev/null
+++ b/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/api/InstancePortEvent.java
@@ -0,0 +1,52 @@
+/*
+ * Copyright 2017-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.openstacknetworking.api;
+
+import org.onosproject.event.AbstractEvent;
+
+/**
+ * Describes virtual instance port event.
+ */
+public class InstancePortEvent extends AbstractEvent<InstancePortEvent.Type, InstancePort> {
+
+    public enum Type {
+
+        /**
+         * Signifies that a new instance port is detected.
+         */
+        OPENSTACK_INSTANCE_PORT_DETECTED,
+
+        /**
+         * Signifies that the instance port is updated.
+         */
+        OPENSTACK_INSTANCE_PORT_UPDATED,
+
+        /**
+         * Signifies that the instance port is disabled.
+         */
+        OPENSTACK_INSTANCE_PORT_VANISHED
+    }
+
+    /**
+     * Creates an event of a given type for the specified instance port.
+     *
+     * @param type     instance port event type
+     * @param instPort instance port
+     */
+    public InstancePortEvent(Type type, InstancePort instPort) {
+        super(type, instPort);
+    }
+}