[jira] [Assigned] (FLINK-12325) Statsd reporter gives wrong metrics when using negative numbers

["Chesnay Schepler (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-12325?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Chesnay Schepler reassigned FLINK-12325:
----------------------------------------

    Assignee: Richard Deurwaarder

> Statsd reporter gives wrong metrics when using negative numbers
> ---------------------------------------------------------------
>
>                 Key: FLINK-12325
>                 URL: https://issues.apache.org/jira/browse/FLINK-12325
>             Project: Flink
>          Issue Type: Bug
>          Components: Runtime / Metrics
>    Affects Versions: 1.6.4, 1.7.2, 1.8.0
>            Reporter: Richard Deurwaarder
>            Assignee: Richard Deurwaarder
>            Priority: Minor
>              Labels: pull-request-available
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> The statsd reporter has a bug I believe when using negative numbers.
>  
> This is because when a metric is sent it is first converted to a string value. This means 100 becomes "100" and -100 becomes "-100". This value is then sent to statsd as a gauge value.
> See this line for the conversion to string: [https://github.com/apache/flink/blob/master/flink-metrics/flink-metrics-statsd/src/main/java/org/apache/flink/metrics/statsd/StatsDReporter.java#L130]
> And this line for sending it as a gauge:
> [https://github.com/apache/flink/blob/master/flink-metrics/flink-metrics-statsd/src/main/java/org/apache/flink/metrics/statsd/StatsDReporter.java#L184]
>  
> This means a value of -100 will be sent like this:
> {code:java}
> <metric_name>:-100|g{code}
>  
> The statsd protocol how ever states the following ([https://github.com/statsd/statsd/blob/master/docs/metric_types.md#gauges]):
> {noformat}
> Adding a sign to the gauge value will change the value, rather than setting it.
> {noformat}
>  
>  
> So sending -100 multiple times means the gauge in statsd will be decremented multiple times, rather than set to -100.
>  
> I believe this isn't how flink expects it to work, is it?



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