1 files changed, 62 insertions, 0 deletions
diff --git a/framework/src/onos/core/api/src/main/java/org/onosproject/store/service/DistributedQueue.java b/framework/src/onos/core/api/src/main/java/org/onosproject/store/service/DistributedQueue.java
new file mode 100644
index 00000000..cc0b00d3
--- /dev/null
+++ b/framework/src/onos/core/api/src/main/java/org/onosproject/store/service/DistributedQueue.java
@@ -0,0 +1,62 @@
+/*
+ * 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;
+
+import java.util.concurrent.CompletableFuture;
+
+/**
+ * A distributed collection designed for holding elements prior to processing.
+ * A queue provides insertion, extraction and inspection operations. The extraction operation
+ * is designed to be non-blocking.
+ *
+ * @param <E> queue entry type
+ */
+public interface DistributedQueue<E> {
+
+    /**
+     * Returns total number of entries in the queue.
+     * @return queue size
+     */
+    long size();
+
+    /**
+     * Returns true if queue has elements in it.
+     * @return true is queue has elements, false otherwise
+     */
+    default boolean isEmpty() {
+        return size() == 0;
+    }
+
+    /**
+     * Inserts an entry into the queue.
+     * @param entry entry to insert
+     */
+    void push(E entry);
+
+    /**
+     * If the queue is non-empty, an entry will be removed from the queue and the returned future
+     * will be immediately completed with it. If queue is empty when this call is made, the returned
+     * future will be eventually completed when an entry is added to the queue.
+     * @return queue entry
+     */
+    CompletableFuture<E> pop();
+
+    /**
+     * Returns an entry from the queue without removing it. If the queue is empty returns null.
+     * @return queue entry or null if queue is empty
+     */
+    E peek();
+}
+\ No newline at end of file