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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