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Posted to dev@kafka.apache.org by "Bill Bejeck (JIRA)" <ji...@apache.org> on 2017/01/05 23:35:58 UTC
[jira] [Assigned] (KAFKA-4601) Avoid duplicated repartitioning in
KStream DSL
[ https://issues.apache.org/jira/browse/KAFKA-4601?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Bill Bejeck reassigned KAFKA-4601:
----------------------------------
Assignee: Bill Bejeck
> 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
> Assignee: Bill Bejeck
> Labels: performance
>
> 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.
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