Support for a distributed counter

Change-Id: I346e9baa28556fac13e53771021f5f6fbcd75ac9
diff --git a/core/api/src/main/java/org/onosproject/store/service/StorageException.java b/core/api/src/main/java/org/onosproject/store/service/StorageException.java
new file mode 100644
index 0000000..a66fc3e
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/store/service/StorageException.java
@@ -0,0 +1,48 @@
+/*
+ * Copyright 2015 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.store.service;
+
+/**
+ * Top level exception for Store failures.
+ */
+@SuppressWarnings("serial")
+public class StorageException extends RuntimeException {
+    public StorageException() {
+    }
+
+    public StorageException(Throwable t) {
+        super(t);
+    }
+
+    /**
+     * Store operation timeout.
+     */
+    public static class Timeout extends StorageException {
+    }
+
+    /**
+     * Store update conflicts with an in flight transaction.
+     */
+    public static class ConcurrentModification extends StorageException {
+    }
+
+    /**
+     * Store operation interrupted.
+     */
+    public static class Interrupted extends StorageException {
+    }
+}