Github user tzulitai commented on a diff in the pull request:
https://github.com/apache/flink/pull/5116#discussion_r156233400
--- Diff:
flink-connectors/flink-connector-kafka-base/src/main/java/org/apache/flink/streaming/connectors/kafka/partitioner/FlinkRoundRobinPartitioner.java
---
@@ -0,0 +1,72 @@
+/*
+ * 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.streaming.connectors.kafka.partitioner;
+
+import org.apache.flink.util.Preconditions;
+
+/**
+ * A partitioner ensuring that each internal Flink partition communicate
with Kafka partition in round robin manner.
+ *
+ * <p>Note, one Kafka partition can contain multiple Flink partitions.
+ *
+ * <p>Cases:
+ * # More Flink partitions than kafka partitions
+ * <pre>
+ * Flink Sinks: Kafka Partitions
+ * 1 ----------------> 1
+ * 2 --------------/
+ * 3 -------------/
+ * 4 ------------/
+ * </pre>
+ * Some (or all) kafka partitions contain the output of more than one
flink partition
+ *
+ * <p>Fewer Flink partitions than Kafka
+ * <pre>
+ * Flink Sinks: Kafka Partitions
+ * 1 ----------------> 1
+ * 2 ----------------> 2
+ *
3
+ *
4
+ *
5
+ * </pre>
+ *
+ * <p>All Kafka partitions contain data
+ * This is a round-robin kafka partitioner (note that this will
+ * cause a lot of network connections between all the Flink instances and
all the Kafka brokers).
+ */
+public class FlinkRoundRobinPartitioner<T> extends
FlinkKafkaPartitioner<T> {
+ private int parallelInstanceId;
--- End diff --
nit: can we have an empty line before the class fields? Just a matter of
taste :)
---
