[jira] [Updated] (KAFKA-13973) block-cache-capacity metrics worth twice as much as normal

["Sylvain Le Gouellec (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-13973?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sylvain Le Gouellec updated KAFKA-13973:
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    Attachment: Screenshot 2022-06-09 at 09.33.50.png

> block-cache-capacity metrics worth twice as much as normal
> ----------------------------------------------------------
>
>                 Key: KAFKA-13973
>                 URL: https://issues.apache.org/jira/browse/KAFKA-13973
>             Project: Kafka
>          Issue Type: Bug
>          Components: streams
>    Affects Versions: 3.2.0
>            Reporter: Sylvain Le Gouellec
>            Priority: Minor
>         Attachments: Screenshot 2022-06-09 at 08.55.36.png, Screenshot 2022-06-09 at 09.33.50.png
>
>
> I have created a very simple kafka-streams application with 1 state store. I'm very surprised that the block-cache-capacity metrics show a {{100MB}} block cache capacity instead of the default one in kafka streams is {{{}50MB{}}}.
>  
> My topology :
> StreamsBuilder sb = new StreamsBuilder();
> sb.stream("input")
>         .groupByKey()
>         .count()
>         .toStream()
>         .to("output");
>  
> I checkout the {{kafka-streams}} code and I saw a strange thing. When the {{{}RocksDBTimestampedStore{}}}store is created, we try to create two column families for backward compatibility with a potentiel old key/value store.
> In this method, {{setDbAccessor(col1, col2)}} if the first column is not valid, well you close this one ([L102|https://github.com/apache/kafka/blob/4542acdc14d5ec3daa1f36d8dc24abc244ee24ff/streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBTimestampedStore.java#L102]). But regarding the rocksdb instance, it's seems that the column families is not deleted completely and the metrics exposed by [Rocksdb continue to aggregate (L373)|https://github.com/apache/kafka/blob/4542acdc14d5ec3daa1f36d8dc24abc244ee24ff/streams/src/main/java/org/apache/kafka/streams/state/internals/metrics/RocksDBMetricsRecorder.java#L373] {{block-cache-capacity }}for both column families (default and keyValueWithTimestamp).
> Maybe you have to drop explicitly the column family, in the {{setDbAccessor(col1, col2)}} if the first column is not valid (like {{{}db.dropColumnFamily(noTimestampColumnFamily);{}}})
>  
> I tried to drop the {{noTimestampColumnFamily in setDbAccessor if the first column is not valid like : }}
>  
> {code:java}
> private void setDbAccessor(final ColumnFamilyHandle noTimestampColumnFamily,
>                            final ColumnFamilyHandle withTimestampColumnFamily) throws RocksDBException {
>     final RocksIterator noTimestampsIter = db.newIterator(noTimestampColumnFamily);
>     noTimestampsIter.seekToFirst();
>     if (noTimestampsIter.isValid()) {
>         log.info("Opening store {} in upgrade mode", name);
>         dbAccessor = new DualColumnFamilyAccessor(noTimestampColumnFamily, withTimestampColumnFamily);
>     } else {
>         log.info("Opening store {} in regular mode", name);
>         dbAccessor = new SingleColumnFamilyAccessor(withTimestampColumnFamily);
>         noTimestampColumnFamily.close();
>         db.dropColumnFamily(noTimestampColumnFamily); // try fix it
>     }
>     noTimestampsIter.close();
> }{code}
>  
>  
>  
> {{But it's seems that you can't drop the default column family in RocksDb (see screenshot).}}
> {{*So how can we have the real block-cache-capacity metrics value in Kafka Streams monitoring ?* }}



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