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https://issues.apache.org/jira/browse/FLINK-9610?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16584000#comment-16584000
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ASF GitHub Bot commented on FLINK-9610:
---------------------------------------
nielsbasjes closed pull request #6181: [FLINK-9610]
[flink-connector-kafka-base] Add Kafka Partitioner that uses the hash of the
provided key.
URL: https://github.com/apache/flink/pull/6181
This is a PR merged from a forked repository.
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diff --git
a/flink-connectors/flink-connector-kafka-base/src/main/java/org/apache/flink/streaming/connectors/kafka/partitioner/FlinkKeyHashPartitioner.java
b/flink-connectors/flink-connector-kafka-base/src/main/java/org/apache/flink/streaming/connectors/kafka/partitioner/FlinkKeyHashPartitioner.java
new file mode 100644
index 00000000000..7a10d6a34a8
--- /dev/null
+++
b/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[Math.abs(hash(key)) % partitions.length];
+ }
+
+ /**
+ * The overridable implementation of the hashing algorithm.
+ * @param key The key of the provided record on which the partition
selection is based. (key can be null!)
+ * @return The hash value for the provided key.
+ */
+ protected int hash(@Nullable byte[] key) {
+ return Arrays.hashCode(key);
+ }
+
+}
diff --git
a/flink-connectors/flink-connector-kafka-base/src/test/java/org/apache/flink/streaming/connectors/kafka/FlinkKeyHashPartitionerTest.java
b/flink-connectors/flink-connector-kafka-base/src/test/java/org/apache/flink/streaming/connectors/kafka/FlinkKeyHashPartitionerTest.java
new file mode 100644
index 00000000000..cdf8afb7181
--- /dev/null
+++
b/flink-connectors/flink-connector-kafka-base/src/test/java/org/apache/flink/streaming/connectors/kafka/FlinkKeyHashPartitionerTest.java
@@ -0,0 +1,108 @@
+/*
+ * 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;
+
+import
org.apache.flink.streaming.connectors.kafka.partitioner.FlinkKeyHashPartitioner;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import javax.annotation.Nullable;
+
+/**
+ * Tests for the {@link FlinkKeyHashPartitioner}.
+ */
+public class FlinkKeyHashPartitionerTest {
+
+ @Test
+ public void testMoreFlinkThanBrokers() {
+ FlinkKeyHashPartitioner<String> part = new
FlinkKeyHashPartitioner<>();
+
+ int[] partitions = new int[]{0, 1};
+
+ part.open(0, 4);
+ Assert.assertEquals(0, part.partition("abc", "abc1".getBytes(),
null, null, partitions));
+
+ part.open(1, 4);
+ Assert.assertEquals(1, part.partition("abc", "abc2".getBytes(),
null, null, partitions));
+
+ part.open(2, 4);
+ Assert.assertEquals(0, part.partition("abc", "abc3".getBytes(),
null, null, partitions));
+ Assert.assertEquals(0, part.partition("abc", "abc3".getBytes(),
null, null, partitions)); // check if it is changing ;)
+
+ part.open(3, 4);
+ Assert.assertEquals(1, part.partition("abc", "abc4".getBytes(),
null, null, partitions));
+ }
+
+ @Test
+ public void testFewerPartitions() {
+ FlinkKeyHashPartitioner<String> part = new
FlinkKeyHashPartitioner<>();
+
+ int[] partitions = new int[]{0, 1, 2, 3, 4};
+ part.open(0, 2);
+ Assert.assertEquals(4, part.partition("abc1",
"abc1".getBytes(), null, null, partitions));
+ Assert.assertEquals(4, part.partition("abc1",
"abc1".getBytes(), null, null, partitions));
+
+ // The resulting kafka partition is dependent ONLY on the key
+ part.open(1, 2);
+ Assert.assertEquals(4, part.partition("abc1",
"abc1".getBytes(), null, null, partitions));
+ Assert.assertEquals(4, part.partition("abc1",
"abc1".getBytes(), null, null, partitions));
+ }
+
+ @Test
+ public void testSameNumber() {
+ FlinkKeyHashPartitioner<String> part = new
FlinkKeyHashPartitioner<>();
+ int[] partitions = new int[]{0, 1, 2};
+
+ part.open(0, 3);
+ Assert.assertEquals(0, part.partition("abc", "abc2".getBytes(),
null, null, partitions));
+
+ part.open(1, 3);
+ Assert.assertEquals(0, part.partition("abc", "abc2".getBytes(),
null, null, partitions));
+
+ part.open(2, 3);
+ Assert.assertEquals(0, part.partition("abc", "abc2".getBytes(),
null, null, partitions));
+ }
+
+ private static class NegativeHashPartitioner<T> extends
FlinkKeyHashPartitioner<T> {
+ private static final long serialVersionUID =
6591915886288619235L;
+ @Override
+ protected int hash(@Nullable byte[] key) {
+ // Force the return value to ALWAYS be nagative for
this test
+ return -1 * Math.abs(super.hash(key));
+ }
+ }
+
+ /**
+ * Ensure it is ok if the hash function returns a negative value.
+ */
+ @Test
+ public void testNegativeHashGuard() {
+ FlinkKeyHashPartitioner<String> part = new
NegativeHashPartitioner<>();
+
+ int[] partitions = new int[]{0, 1};
+
+ part.open(0, 4);
+ Assert.assertEquals(0, part.partition("abc", "abc1".getBytes(),
null, null, partitions));
+ Assert.assertEquals(1, part.partition("abc", "abc2".getBytes(),
null, null, partitions));
+ Assert.assertEquals(0, part.partition("abc", "abc3".getBytes(),
null, null, partitions));
+ Assert.assertEquals(1, part.partition("abc", "abc4".getBytes(),
null, null, partitions));
+ }
+
+}
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> Add Kafka partitioner that uses the key to partition by
> -------------------------------------------------------
>
> Key: FLINK-9610
> URL: https://issues.apache.org/jira/browse/FLINK-9610
> Project: Flink
> Issue Type: New Feature
> Components: Kafka Connector
> Reporter: Niels Basjes
> Assignee: Niels Basjes
> Priority: Major
> Labels: pull-request-available
>
> The kafka connector package only contains the FlinkFixedPartitioner
> implementation of the FlinkKafkaPartitioner.
> The most common usecase I have seen is the need to spread the records across
> the Kafka partitions while keeping all messages with the same key together.
> I'll put up a pull request with a very simple implementation that should make
> this a lot easier for others to use and extend.
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