ONOS-2322: Support for periodic purging of ECMap tombstones

Change-Id: I6fe5475a472c383c4a51bd61446fba8f1dba1d37
diff --git a/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/AntiEntropyResponse.java b/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/AntiEntropyResponse.java
new file mode 100644
index 0000000..f6a03b5
--- /dev/null
+++ b/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/AntiEntropyResponse.java
@@ -0,0 +1,37 @@
+/*
+ * Copyright 2016-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.store.primitives.impl;
+
+/**
+ * Status of anti-entropy exchange, returned by the receiver.
+ *
+ */
+public enum AntiEntropyResponse {
+    /**
+     * Signifies a successfully processed anti-entropy message.
+     */
+    PROCESSED,
+
+    /**
+     * Signifies a unexpected failure during anti-entropy message processing.
+     */
+    FAILED,
+
+    /**
+     * Signifies a ignored anti-entropy message, potentially due to the receiver operating under high load.
+     */
+    IGNORED
+}
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