[jira] [Created] (KAFKA-19689) TopologyTestDriver spends most of its time forcing changes to disk

["Steven Schlansker (Jira)" <ji...@apache.org>]

Steven Schlansker created KAFKA-19689:
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             Summary: TopologyTestDriver spends most of its time forcing changes to disk
                 Key: KAFKA-19689
                 URL: https://issues.apache.org/jira/browse/KAFKA-19689
             Project: Kafka
          Issue Type: Improvement
          Components: streams-test-utils
    Affects Versions: 4.1.0
            Reporter: Steven Schlansker
         Attachments: image-2025-09-08-14-07-05-768.png

We recently upgraded a Streams app to 4.1.0 and found that our unit and integration tests feel like they take much longer and consume more system resources. Indeed, when comparing to 4.0.0, it seems there is a significant regression in the TopologyTestDriver - with 4.1.0, we spend a ton of time in {{Utils.flushDir}} that did not seem to happen in 4.0.0

It looks like the test driver is syncing the entire state directory to disk for every record processed:

!image-2025-09-08-14-07-05-768.png!



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