[jira] [Resolved] (KAFKA-7660) Stream Metrics - Memory Analysis

["Guozhang Wang (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-7660?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Guozhang Wang resolved KAFKA-7660.
----------------------------------
       Resolution: Fixed
         Assignee: John Roesler
    Fix Version/s: 2.2.0

> Stream Metrics - Memory Analysis
> --------------------------------
>
>                 Key: KAFKA-7660
>                 URL: https://issues.apache.org/jira/browse/KAFKA-7660
>             Project: Kafka
>          Issue Type: Bug
>          Components: metrics, streams
>    Affects Versions: 2.0.0
>            Reporter: Patrik Kleindl
>            Assignee: John Roesler
>            Priority: Minor
>             Fix For: 2.2.0
>
>         Attachments: Mem_Collections.jpeg, Mem_DuplicateStrings.jpeg, Mem_DuplicateStrings2.jpeg, Mem_Hotspots.jpeg, Mem_KeepAliveSet.jpeg, Mem_References.jpeg, heapdump-1543441898901.hprof
>
>
> 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.
>  
> The analysis was done with Dynatrace 7.0
> We are running Confluent 5.0/Kafka2.0-cp1 (Brokers as well as Clients)
>  
> Screenshots are attached.



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