RFR: 8284: Fix Jolokia discovery issues

[Alex Macdonald]

On Wed, 30 Oct 2024 19:00:52 GMT, Martin Skarsaune <duke at openjdk.org> wrote:

>> This fixes two bugs with Jolokia discovery:
>> 1. serious : repeated discovery runs crash. Runing repeatedly in the background is the whole point
>> 2. more of an annoyance: the PR disables JMC agent by omitting JVM info in the descriptor (as presence is interpreted as a local JVM)
>> Both tested OK.
>
> @aptmac : Are you able to create a bug for this. Or two if that is preferrable. 
> Details on the bugs:
> 
> 1. 
> 
> SEVERE: Cannot register MBean jolokia:type=Discovery,agent=jmc: javax.management.InstanceAlreadyExistsException: jolokia:type=Discovery,agent=jmc
> javax.management.InstanceAlreadyExistsException: jolokia:type=Discovery,agent=jmc
> 	at java.management/com.sun.jmx.mbeanserver.Repository.addMBean(Repository.java:322)
> 	at java.management/com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerWithRepository(DefaultMBeanServerInterceptor.java:1848)
> 	at java.management/com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerDynamicMBean(DefaultMBeanServerInterceptor.java:945)
> 	at java.management/com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerObject(DefaultMBeanServerInterceptor.java:880)
> 	at java.management/com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerMBean(DefaultMBeanServerInterceptor.java:315)
> 	at java.management/com.sun.jmx.mbeanserver.JmxMBeanServer.registerMBean(JmxMBeanServer.java:523)
> 	at org.jolokia.server.core.service.impl.MBeanRegistry.registerMBeanAtServer(MBeanRegistry.java:80)
> 	at org.jolokia.server.core.service.impl.MBeanRegistry.registerMBean(MBeanRegistry.java:54)
> 	at org.jolokia.server.core.service.impl.JolokiaServiceManagerImpl.registerMBean(JolokiaServiceManagerImpl.java:409)
> 	at org.jolokia.server.core.service.impl.JolokiaContextImpl.registerMBean(JolokiaContextImpl.java:45)
> 	at org.jolokia.server.core.service.api.AbstractJolokiaService.registerJolokiaMBean(AbstractJolokiaService.java:98)
> 	at org.jolokia.service.discovery.JolokiaDiscovery.init(JolokiaDiscovery.java:45)
> 	at org.openjdk.jmc.jolokia.JolokiaDiscoveryListener.discoverJvms(JolokiaDiscoveryListener.java:70)
> 	at org.openjdk.jmc.jolokia.AbstractCachedDescriptorProvider$Scanner.scan(AbstractCachedDescriptorProvider.java:86)
> 	at org.openjdk.jmc.jolokia.AbstractCachedDescriptorProvider$Scanner.run(AbstractCachedDescriptorProvider.java:70)
> 	at java.base/java.lang.Thread.run(Thread.java:1583)
> 
> 2. This option does not make sense for Jolokia:
> 
> <img width="870" alt="image" src="https://github.com/user-attachments/assets/d28873bd-10b5-4753-9964-2dfb6a451496">

@skarsaune I've rolled both of these issues into one ticket if that's okay, I think it fits with this PR that accomplishes both at once.

https://bugs.openjdk.org/browse/JMC-8284

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PR Comment: https://git.openjdk.org/jmc/pull/597#issuecomment-2450086793