Hello

During the analysis of JVM memory two possible issues were shown which I
would like to bring to your attention:
1) Duplicate strings
Top findings:
string_content="stream-processor-node-metrics" count="534,277"
string_content="processor-node-id" count="148,437"
string_content="stream-rocksdb-state-metrics" count="41,832"
string_content="punctuate-latency-avg" count="29,681"

"stream-processor-node-metrics"  seems to be used in Sensors.java as a
literal and not interned.

2) The HashMap parentSensors
from 
org.apache.kafka.streams.processor.internals.StreamThread$StreamsMetricsThreadImpl
was reported multiple times as suspicious for potentially keeping alive a
lot of objects. In our case the reported size was 40-50MB each.
I haven't looked too deep in the code but noticed that the class
Sensor.java which is used as a key in the HashMap does not implement equals
or hashCode method. Not sure this is a problem though.

Maybe someone can shed some light on this

best regards

Patrik

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