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https://issues.apache.org/jira/browse/KAFKA-9603?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17046169#comment-17046169
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Sophie Blee-Goldman commented on KAFKA-9603:
--------------------------------------------
Admittedly a day does seem like a long time, but the rocksdb background
compaction may merge the small L0 files less aggressively once they're under a
certain threshold...just a wild guess. Do you mean the large number of files
continues to grow up to 24hr after restoration completes, or just that it goes
up during restoration and doesn't go back down again for a day?
If you can increase the limit I'd recommend starting there, if you have a large
number of stores/task or tasks/instance then the open files can really build
up.
> 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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