[jira] [Assigned] (KAFKA-17954) Error getting oldest-iterator-open-since-ms from JMX

["Nicholas Telford (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-17954?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Nicholas Telford reassigned KAFKA-17954:
----------------------------------------

    Assignee: Nicholas Telford

> Error getting oldest-iterator-open-since-ms from JMX
> ----------------------------------------------------
>
>                 Key: KAFKA-17954
>                 URL: https://issues.apache.org/jira/browse/KAFKA-17954
>             Project: Kafka
>          Issue Type: Bug
>          Components: streams
>    Affects Versions: 3.8.1
>            Reporter: Nicholas Telford
>            Assignee: Nicholas Telford
>            Priority: Minor
>
> In [KIP-989|https://cwiki.apache.org/confluence/display/KAFKA/KIP-989%3A+Improved+StateStore+Iterator+metrics+for+detecting+leaks] we introduced a new metric, {{{}oldest-iterator-open-since-ms{}}}, which reports the timestamp that the oldest currently open KeyValueIterator was opened at.
> However, if no iterators are currently open, this Gauge returns {{{}null{}}}.
> When using the Prometheus {{JmxScraper}} to scrape this metric, its value is added to a {{{}ConcurrentHashMap{}}}, which does _not_ permit {{null}} values.
> Consequently, on-scrape, we see this {{WARN}} log message:
> {noformat}
> Error getting JMX attribute 'oldest-iterator-open-since-ms' {noformat}
> We should find some other way to report the absence of this metric that does not cause problems with {{{}ConcurrentHashMap{}}}.



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