[ONOS-7054] Implement prototype of ISSU protocol
Change-Id: Id543c0de9c97b68f977c824cbc987b35d81beb2d
diff --git a/core/api/src/main/java/org/onosproject/store/cluster/messaging/ClusterCommunicator.java b/core/api/src/main/java/org/onosproject/store/cluster/messaging/ClusterCommunicator.java
new file mode 100644
index 0000000..7d2480e
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/store/cluster/messaging/ClusterCommunicator.java
@@ -0,0 +1,166 @@
+/*
+ * Copyright 2017-present Open Networking Foundation
+ *
+ * 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.cluster.messaging;
+
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorService;
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+import org.onosproject.cluster.NodeId;
+
+/**
+ * Service for assisting communications between controller cluster nodes.
+ */
+public interface ClusterCommunicator {
+
+ /**
+ * Adds a new subscriber for the specified message subject.
+ *
+ * @param subject message subject
+ * @param subscriber message subscriber
+ * @param executor executor to use for running handler.
+ * @deprecated in Cardinal Release
+ */
+ @Deprecated
+ void addSubscriber(MessageSubject subject, ClusterMessageHandler subscriber, ExecutorService executor);
+
+ /**
+ * Broadcasts a message to all controller nodes.
+ *
+ * @param message message to send
+ * @param subject message subject
+ * @param encoder function for encoding message to byte[]
+ * @param <M> message type
+ */
+ <M> void broadcast(M message,
+ MessageSubject subject,
+ Function<M, byte[]> encoder);
+
+ /**
+ * Broadcasts a message to all controller nodes including self.
+ *
+ * @param message message to send
+ * @param subject message subject
+ * @param encoder function for encoding message to byte[]
+ * @param <M> message type
+ */
+ <M> void broadcastIncludeSelf(M message,
+ MessageSubject subject,
+ Function<M, byte[]> encoder);
+
+ /**
+ * Sends a message to the specified controller node.
+ *
+ * @param message message to send
+ * @param subject message subject
+ * @param encoder function for encoding message to byte[]
+ * @param toNodeId destination node identifier
+ * @param <M> message type
+ * @return future that is completed when the message is sent
+ */
+ <M> CompletableFuture<Void> unicast(M message,
+ MessageSubject subject,
+ Function<M, byte[]> encoder,
+ NodeId toNodeId);
+
+ /**
+ * Multicasts a message to a set of controller nodes.
+ *
+ * @param message message to send
+ * @param subject message subject
+ * @param encoder function for encoding message to byte[]
+ * @param nodeIds recipient node identifiers
+ * @param <M> message type
+ */
+ <M> void multicast(M message,
+ MessageSubject subject,
+ Function<M, byte[]> encoder,
+ Set<NodeId> nodeIds);
+
+ /**
+ * Sends a message and expects a reply.
+ *
+ * @param message message to send
+ * @param subject message subject
+ * @param encoder function for encoding request to byte[]
+ * @param decoder function for decoding response from byte[]
+ * @param toNodeId recipient node identifier
+ * @param <M> request type
+ * @param <R> reply type
+ * @return reply future
+ */
+ <M, R> CompletableFuture<R> sendAndReceive(M message,
+ MessageSubject subject,
+ Function<M, byte[]> encoder,
+ Function<byte[], R> decoder,
+ NodeId toNodeId);
+
+ /**
+ * Adds a new subscriber for the specified message subject.
+ *
+ * @param subject message subject
+ * @param decoder decoder for resurrecting incoming message
+ * @param handler handler function that processes the incoming message and produces a reply
+ * @param encoder encoder for serializing reply
+ * @param executor executor to run this handler on
+ * @param <M> incoming message type
+ * @param <R> reply message type
+ */
+ <M, R> void addSubscriber(MessageSubject subject,
+ Function<byte[], M> decoder,
+ Function<M, R> handler,
+ Function<R, byte[]> encoder,
+ Executor executor);
+
+ /**
+ * Adds a new subscriber for the specified message subject.
+ *
+ * @param subject message subject
+ * @param decoder decoder for resurrecting incoming message
+ * @param handler handler function that processes the incoming message and produces a reply
+ * @param encoder encoder for serializing reply
+ * @param <M> incoming message type
+ * @param <R> reply message type
+ */
+ <M, R> void addSubscriber(MessageSubject subject,
+ Function<byte[], M> decoder,
+ Function<M, CompletableFuture<R>> handler,
+ Function<R, byte[]> encoder);
+
+ /**
+ * Adds a new subscriber for the specified message subject.
+ *
+ * @param subject message subject
+ * @param decoder decoder to resurrecting incoming message
+ * @param handler handler for handling message
+ * @param executor executor to run this handler on
+ * @param <M> incoming message type
+ */
+ <M> void addSubscriber(MessageSubject subject,
+ Function<byte[], M> decoder,
+ Consumer<M> handler,
+ Executor executor);
+
+ /**
+ * Removes a subscriber for the specified message subject.
+ *
+ * @param subject message subject
+ */
+ void removeSubscriber(MessageSubject subject);
+}