Guozhang Wang created KAFKA-4601: ------------------------------------ Summary: Avoid duplicated repartitioning in KStream DSL Key: KAFKA-4601 URL: https://issues.apache.org/jira/browse/KAFKA-4601 Project: Kafka Issue Type: Bug Components: streams Reporter: Guozhang Wang
Consider the following DSL: {code} Stream<String, String> source = builder.stream(Serdes.String(), Serdes.String(), "topic1").map(..); KTable<String, Long> counts = source .groupByKey() .count("Counts"); KStream<String, String> sink = source.leftJoin(counts, ..); {code} The resulted topology looks like this: {code} ProcessorTopology: KSTREAM-SOURCE-0000000000: topics: [topic1] children: [KSTREAM-MAP-0000000001] KSTREAM-MAP-0000000001: children: [KSTREAM-FILTER-0000000004, KSTREAM-FILTER-0000000007] KSTREAM-FILTER-0000000004: children: [KSTREAM-SINK-0000000003] KSTREAM-SINK-0000000003: topic: X-Counts-repartition KSTREAM-FILTER-0000000007: children: [KSTREAM-SINK-0000000006] KSTREAM-SINK-0000000006: topic: X-KSTREAM-MAP-0000000001-repartition ProcessorTopology: KSTREAM-SOURCE-0000000008: topics: [X-KSTREAM-MAP-0000000001-repartition] children: [KSTREAM-LEFTJOIN-0000000009] KSTREAM-LEFTJOIN-0000000009: states: [Counts] KSTREAM-SOURCE-0000000005: topics: [X-Counts-repartition] children: [KSTREAM-AGGREGATE-0000000002] KSTREAM-AGGREGATE-0000000002: states: [Counts] {code} I.e. there are two repartition topics, one for the aggregate and one for the join, which not only introduce unnecessary overheads but also mess up the processing ordering (users are expecting each record to go through aggregation first then the join operator). And in order to get the following simpler topology users today need to add a {{through}} operator after {{map}} manually to enforce repartitioning. {code} ProcessorTopology: KSTREAM-SOURCE-0000000000: topics: [topic1] children: [KSTREAM-MAP-0000000001] KSTREAM-MAP-0000000001: children: [KSTREAM-SINK-0000000002] KSTREAM-SINK-0000000002: topic: topic 2 ProcessorTopology: KSTREAM-SOURCE-0000000003: topics: [topic 2] children: [KSTREAM-AGGREGATE-0000000004, KSTREAM-LEFTJOIN-0000000005] KSTREAM-AGGREGATE-0000000004: states: [Counts] KSTREAM-LEFTJOIN-0000000005: states: [Counts] {code} This kind of optimization should be automatic in Streams, which we can consider doing when extending from one-operator-at-a-time translation. -- This message was sent by Atlassian JIRA (v6.3.4#6332)