[jira] [Created] (KAFKA-9603) Number of open files keeps increasing in Streams application

["Bruno Iljazovic (Jira)" <ji...@apache.org>]

Bruno Iljazovic created KAFKA-9603:
--------------------------------------

             Summary: 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: 2.3.1, 2.4.0
         Environment: Spring Boot 2.2.4, OpenJDK 13, Centos image
            Reporter: Bruno Iljazovic


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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