JMX metrics for Tomcat with 'Tomcat' JMX domain #10115
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When using the JMX Insights feature with a spring-boot application, I noticed that the JMX metrics were not captured when setting
OTEL_JMX_TARGET_SYSTEM=tomcat.The problem is that the JMX MBeans are registered with
Tomcatdomain instead ofCatalina, and thus the rules do not match.With standalone tomcat servers (tested latest 8.5, 9.0.x and 10.x), the JMX domain is always
Catalina. I am not an expert in Tomcat internals but this comes from the implementation oforg.apache.catalina.util.LifecycleMBeanBase#getDomainthat returns any sub-class implementation oforg.apache.catalina.util.LifecycleMBeanBase#getDomainInternaland falls back toCatalina.Searching for the
Tomcat:string in the Tomcat codebase seems to indicate that this is quite a common value, for example here in tests.While we could use a wildcard in the rules for the JMX domain, for example
*:type=GlobalRequestProcessor,name=*in place ofCatalina:type=GlobalRequestProcessor,name=*, that might also introduce false-positives if other application servers also have similar named MBeans, thus duplication sounds the best compromize here.