Sometimes mBeans produce errors when scraped by the JMX exporter. Being able to look at detailed logs can help you figure out exactly which mBean is having issues and why.
Create a file called logging.properties with this content:
handlers=java.util.logging.ConsoleHandler java.util.logging.ConsoleHandler.level=ALL io.prometheus.jmx.level=ALL io.prometheus.jmx.shaded.io.prometheus.jmx.level=ALL
Add the following flag to your Java invocation:
-Djava.util.logging.config.file=/path/to/logging.properties
If you run your application you'll now see logs on standard error.
If you already have a log handler such as logback, log4j or slf4j you should adjust their configs along the lines shown.
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