Github user tillrohrmann commented on a diff in the pull request:
https://github.com/apache/flink/pull/917#discussion_r35214927
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/akka/FlinkUntypedActor.java
---
@@ -0,0 +1,140 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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.apache.flink.runtime.akka;
+
+import akka.actor.UntypedActor;
+import
org.apache.flink.runtime.messages.JobManagerMessages.LeaderSessionMessage;
+import org.apache.flink.runtime.messages.RequiresLeaderSessionID;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import scala.Option;
+
+import java.util.UUID;
+
+/**
+ * Base class for Flink's actors implemented with Java. Actors inheriting
from this class
+ * automatically log received messages when the debug log level is
activated. Furthermore,
+ * they filter out {@link LeaderSessionMessage} with the wrong leader
session ID. If a message
+ * of type {@link RequiresLeaderSessionID} without being wrapped in a
LeaderSessionMessage is
+ * detected, then an Exception is thrown.
+ *
+ * In order to implement the actor behavior, an implementing subclass has
to override the method
+ * handleMessage, which defines how messages are processed. Furthermore,
the subclass has to provide
+ * a leader session ID option which is returned by getLeaderSessionID.
+ */
+abstract public class FlinkUntypedActor extends UntypedActor {
+ protected static Logger LOG =
LoggerFactory.getLogger(FlinkUntypedActor.class);
+
+ /**
+ * This method is called by Akka if a new message has arrived for the
actor. It logs the
+ * processing time of the incoming message if the logging level is set
to debug. After logging
+ * the handleLeaderSessionID method is called.
+ *
+ * Important: This method cannot be overriden. The actor specific
message handling logic is
+ * implemented by the method handleMessage.
+ *
+ * @param message Incoming message
+ * @throws Exception
+ */
+ @Override
+ public final void onReceive(Object message) throws Exception {
+ if(LOG.isDebugEnabled()) {
+ LOG.debug("Received message {} at {} from {}.",
message, getSelf().path(), getSender());
+
+ long start = System.nanoTime();
+
+ handleLeaderSessionID(message);
+
+ long duration = (System.nanoTime() - start)/ 1000000;
+
+ LOG.debug("Handled message {} in {} ms from {}.",
message, duration, getSender());
+ } else {
+ handleLeaderSessionID(message);
+ }
+ }
+
+ /**
+ * This method filters out {@link LeaderSessionMessage} whose leader
session ID is not equal
+ * to the actors leader session ID. If a message of type {@link
RequiresLeaderSessionID}
+ * arrives, then an Exception is thrown, because these messages have to
be wrapped in a
+ * {@link LeaderSessionMessage}.
+ *
+ * @param message Incoming message
+ * @throws Exception
+ */
+ private void handleLeaderSessionID(Object message) throws Exception {
+ if(message instanceof LeaderSessionMessage) {
+ LeaderSessionMessage msg = (LeaderSessionMessage)
message;
+
+ if(msg.leaderSessionID().isDefined() &&
getLeaderSessionID().isDefined()) {
+
if(getLeaderSessionID().equals(msg.leaderSessionID())) {
+ // finally call method to handle message
+ handleMessage(msg.message());
+ } else {
+ handleDiscardedMessage(msg);
+ }
+ } else {
+ handleDiscardedMessage(msg);
+ }
+ } else if (message instanceof RequiresLeaderSessionID) {
+ throw new Exception("Received a message " + message + "
without a leader session " +
+ "ID, even though it requires to have
one.");
+ } else {
+ // call method to handle message
+ handleMessage(message);
+ }
+ }
+
+ private void handleDiscardedMessage(Object msg) {
+ LOG.debug("Discard message {} because the leader session ID was
not correct.", msg);
+ }
+
+ /**
+ * This method contains the actor logic which defines how to react to
incoming messages.
+ *
+ * @param message Incoming message
+ * @throws Exception
+ */
+ abstract protected void handleMessage(Object message) throws Exception;
--- End diff --
Good point. I'm always unsure about this point. Will update it.
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---
