Explicit Exception for Duplicate Labels during Scrape

[fstab]

When a collector produces duplicate labels (same metric name, same label names, same label values) during scrape, client_java throws an IllegalArgumentException.

client_java/prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/MetricSnapshot.java

Line 46 in f1cc00a

throw new IllegalArgumentException("Duplicate labels in metric data: " + dataPoints.get(i).getLabels());

It would be better to have an explicit Exception for that so the collector can catch it. This would help with prometheus/jmx_exporter#911 (comment)

[dhoard]

Looking at the code, MetricSnapshot has the MetricMetadata which could be added to the exception. This would provide more information about the configuration issue.