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

[Shang Yuanchun (Jira)]

Richard Deurwaarder created FLINK-12325:
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             Summary: 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: 1.8.0, 1.7.2, 1.6.4
            Reporter: Richard Deurwaarder


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]

 

So 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, isn't it?



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