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https://issues.apache.org/jira/browse/KAFKA-9603?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17093312#comment-17093312
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Bruno Iljazovic commented on KAFKA-9603:
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To expand on this, it seems that RocksDB version doesn't affect this problem.
Instead, from Streams version 2.1.0 on, when two instances of consumer
applications are started, auto compaction in RocksDB is disabled for *standby
tasks* on both instances. Furthermore, when one instance is paused, then
resumed, then same with the other instance, both instances compact their stores
normally.
> Number of open files keeps increasing in Streams application
> ------------------------------------------------------------
>
> Key: KAFKA-9603
> URL: https://issues.apache.org/jira/browse/KAFKA-9603
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Affects Versions: 2.4.0, 2.3.1
> Environment: Spring Boot 2.2.4, OpenJDK 13, Centos image
> Reporter: Bruno Iljazovic
> Priority: Major
>
> Problem appeared when upgrading from *2.0.1* to *2.3.1*.
> Relevant Kafka Streams code:
> {code:java}
> KStream<String, Event1> events1 =
> builder.stream(FIRST_TOPIC_NAME, Consumed.with(stringSerde, event1Serde,
> event1TimestampExtractor(), null))
> .mapValues(...);
> KStream<String, Event2> events2 =
> builder.stream(SECOND_TOPIC_NAME, Consumed.with(stringSerde, event2Serde,
> event2TimestampExtractor(), null))
> .mapValues(...);
> var joinWindows = JoinWindows.of(Duration.of(1, MINUTES).toMillis())
> .until(Duration.of(1, HOURS).toMillis());
> events2.join(events1, this::join, joinWindows, Joined.with(stringSerde,
> event2Serde, event1Serde))
> .foreach(...);
> {code}
> Number of open *.sst files keeps increasing until eventually it hits the os
> limit (65536) and causes this exception:
> {code:java}
> Caused by: org.rocksdb.RocksDBException: While open a file for appending:
> /.../0_8/KSTREAM-JOINOTHER-0000000010-store/KSTREAM-JOINOTHER-0000000010-store.1579435200000/001354.sst:
> Too many open files
> at org.rocksdb.RocksDB.flush(Native Method)
> at org.rocksdb.RocksDB.flush(RocksDB.java:2394)
> {code}
> Here are example files that are opened and never closed:
> {code:java}
> /.../0_27/KSTREAM-JOINTHIS-0000000009-store/KSTREAM-JOINTHIS-0000000009-store.1582459200000/000114.sst
> /.../0_27/KSTREAM-JOINOTHER-0000000010-store/KSTREAM-JOINOTHER-0000000010-store.1582459200000/000065.sst
> /.../0_29/KSTREAM-JOINTHIS-0000000009-store/KSTREAM-JOINTHIS-0000000009-store.1582156800000/000115.sst
> /.../0_29/KSTREAM-JOINTHIS-0000000009-store/KSTREAM-JOINTHIS-0000000009-store.1582459200000/000112.sst
> /.../0_31/KSTREAM-JOINTHIS-0000000009-store/KSTREAM-JOINTHIS-0000000009-store.1581854400000/000051.sst
> {code}
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