[GitHub] [beam] damccorm opened a new issue, #20635: FlinkDistributionGauge and FlinkGauge metrics are exported as zero to Prometheus when using any Flink's PrometheusReporter

[GitBox <gi...@apache.org>]

damccorm opened a new issue, #20635:
URL: https://github.com/apache/beam/issues/20635

   To be honest I'm really lost on this one, let me explain the issue:
   
   Beam has its own metrics types (org/apache/beam/sdk/metrics/Metrics.java) \-counter, distribution, and gauge\-, and, depending on the runner, wraps them into their corresponding runner types. For example, for Flink, Beam is wrapping its Gauge type into a class called FlinkGauge which extends a Gauge<Long\>.
   
   Also, Beam's Distribution metric its wrapped into a Flink's Gauge<DistributionResult\>, where DistributionResult is a Beam type containing min,max,sum,count.
   
   Then, if you are using Flink, and you want to export those metrics to Prometheus, using flink-metrics-prometheus, you will see that they are always zero, and, if you set DEBUG log level for  "org.apache.flink.metrics.prometheus" package, you will see errors like following ones:
   ```
   
   2020-09-18 06:27:04,387 DEBUG Invalid type for Gauge org.apache.beam.runners.flink.metrics.FlinkMetricContainer$FlinkDistributionGauge@30211d3f:
   org.apache.beam.sdk.metrics.AutoValue_DistributionResult, only number types and booleans are supported
   by this reporter.
   2020-09-18 06:27:04,394 DEBUG Invalid type for Gauge org.apache.beam.runners.flink.metrics.FlinkMetricContainer$FlinkGauge@2ad1562:
   org.apache.beam.sdk.metrics.AutoValue_GaugeResult, only number types and booleans are supported by this
   reporter.
   
   ```
   
   
   Which is really weird, because if you check the source code of AbstractPrometheusReporter, you can see that is taking the metric value from Flink's Gauge using getValue():
   https://github.com/apache/flink/blob/master/flink-metrics/flink-metrics-prometheus/src/main/java/org/apache/flink/metrics/prometheus/AbstractPrometheusReporter.java#L225
   
   And FlinkGauge.getValue() should return a long instead of org.apache.beam.sdk.metrics.AutoValue_GaugeResult. So I don't understand what is happening there to be honest. May be AutoValue mechanism is messing things up?
   
   Imported from Jira [BEAM-10928](https://issues.apache.org/jira/browse/BEAM-10928). Original Jira may contain additional context.
   Reported by: ivansjg.


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