Github user tedyu commented on a diff in the pull request:
https://github.com/apache/flink/pull/6181#discussion_r196368052
--- Diff:
flink-connectors/flink-connector-kafka-base/src/main/java/org/apache/flink/streaming/connectors/kafka/partitioner/FlinkKeyHashPartitioner.java
---
@@ -0,0 +1,60 @@
+/*
+ * 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.annotation.PublicEvolving;
+import org.apache.flink.util.Preconditions;
+
+import javax.annotation.Nullable;
+
+import java.util.Arrays;
+
+/**
+ * A partitioner that uses the hash of the provided key to distribute
+ * the values over the partitions as evenly as possible.
+ * This partitioner ensures that all records with the same key will be
sent to
+ * the same Kafka partition.
+ *
+ * <p>Note that this will cause a lot of network connections to be created
between
+ * all the Flink instances and all the Kafka brokers.
+ */
+@PublicEvolving
+public class FlinkKeyHashPartitioner<T> extends FlinkKafkaPartitioner<T> {
+
+ private static final long serialVersionUID = -2006468063065010594L;
+
+ @Override
+ public int partition(T record, byte[] key, byte[] value, String
targetTopic, int[] partitions) {
+ Preconditions.checkArgument(
+ partitions != null && partitions.length > 0,
+ "Partitions of the target topic is empty.");
+
+ return partitions[hash(key) % partitions.length];
--- End diff --
Should we guard against hash(key) % partitions.length < 0 (in case someone
overrides hash()) ?
---
