Github user olegz commented on a diff in the pull request:
https://github.com/apache/nifi/pull/295#discussion_r57040700
--- Diff:
nifi-nar-bundles/nifi-kafka-bundle/nifi-kafka-processors/src/main/java/org/apache/nifi/processors/kafka/Partitioners.java
---
@@ -0,0 +1,87 @@
+/*
+ * 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.nifi.processors.kafka;
+
+import java.util.Random;
+
+import kafka.producer.Partitioner;
+import kafka.utils.VerifiableProperties;
+
+/**
+ * Collection of implementation of common Kafka {@link Partitioner}s.
+ */
+final public class Partitioners {
+
+ private Partitioners() {
+ }
+ /**
+ * {@link Partitioner} that implements 'round-robin' mechanism which
evenly
+ * distributes load between all available partitions.
+ */
+ public static class RoundRobinPartitioner implements Partitioner {
+ private volatile int index;
--- End diff --
The use of volatile has two meanings and in this case it's to ensure the
visibility between the threads (basically T1 sets the value and T2 must see it
right after it's been set. Without volatile it is actually not guaranteed.
Think eventual consistency). It was never meant to enforce sequential
distribution since in multi-threaded environment it's somewhat menaingless
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