[GitHub] twalthr commented on a change in pull request #6440: [FLINK-9979] [table] Support a FlinkKafkaPartitioner for Kafka table sink factory

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twalthr commented on a change in pull request #6440: [FLINK-9979] [table] Support a FlinkKafkaPartitioner for Kafka table sink factory
URL: https://github.com/apache/flink/pull/6440#discussion_r206842240
 
 

 ##########
 File path: flink-connectors/flink-connector-kafka-base/src/main/java/org/apache/flink/table/descriptors/Kafka.java
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 @@ -175,6 +183,69 @@ public Kafka startFromSpecificOffset(int partition, long specificOffset) {
 		return this;
 	}
 
+	/**
+	 * Configures how to partition records from Flink's partitions into Kafka's partitions.
+	 *
+	 * <p>This strategy ensures that each Flink partition ends up in one Kafka partition.
+	 *
+	 * <p>Note: One Kafka partition can contain multiple Flink partitions. Examples:
+	 *
+	 * <p>More Flink partitions than Kafka partitions. Some (or all) Kafka partitions contain
+	 * the output of more than one flink partition:
+	 * <pre>
+	 *     Flink Sinks            Kafka Partitions
+	 *         1    ----------------&gt;    1
+	 *         2    --------------/
+	 *         3    -------------/
+	 *         4    ------------/
+	 * </pre>
+	 *
+	 *
+	 * <p>Fewer Flink partitions than Kafka partitions:
+	 * <pre>
+	 *     Flink Sinks            Kafka Partitions
+	 *         1    ----------------&gt;    1
+	 *         2    ----------------&gt;    2
+	 *                                      3
+	 *                                      4
+	 *                                      5
+	 * </pre>
+	 *
+	 * @see org.apache.flink.streaming.connectors.kafka.partitioner.FlinkFixedPartitioner
+	 */
+	public Kafka sinkPartitionerFixed() {
+		sinkPartitioner = CONNECTOR_SINK_PARTITIONER_VALUE_FIXED;
+		sinkPartitionerClass = null;
+		return this;
+	}
+
+	/**
+	 * Configures how to partition records from Flink's partitions into Kafka's partitions.
+	 *
+	 * <p>This strategy ensures that records will be distributed to Kafka partitions in a
+	 * round-robin fashion.
+	 *
+	 * <p>Note: This strategy is useful to avoid an unbalanced partitioning. However, it will
+	 * cause a lot of network connections between all the Flink instances and all the Kafka brokers.
+	 */
+	public Kafka sinkPartitionerRoundRobin() {
+		sinkPartitioner = CONNECTOR_SINK_PARTITIONER_VALUE_ROUND_ROBIN;
+		sinkPartitionerClass = null;
+		return this;
+	}
+
+	/**
+	 * Configures how to partition records from Flink's partitions into Kafka's partitions.
+	 *
+	 * <p>This strategy allows for a custom partitioner by providing an implementation
+	 * of {@link FlinkKafkaPartitioner}.
+	 */
+	public Kafka sinkPartitionerCustom(Class<? extends FlinkKafkaPartitioner> partitionerClass) {
 
 Review comment:
   The goal was actually to have a single point of validation. Currently, the validation happens when converting the class into string-properties.
   
   If we would allow an instance here, this instance would need to be serialized into a string and deserialized again. We can still allow an instance in the future but for now I would not make it too complicated.

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