Cryostat 3.0 usage issues #595
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Hi, I installed cryostat for evaluation via helm chart. The discovery works, I can see targets and some basic stats via mbeans, however i.e.:
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Replies: 2 comments 26 replies
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actually I see some warning but no clue what is the reason or how to check for details ... 
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@andrewazores makes sense. I am more like platform engineer, how can I find which module should be added ? I mean containing |
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I'm not quite sure - I'm still trying to piece together exactly what is happening here. As far as I can tell, the MissionControl/MissionControlMXBean only exists in JDK 7 and 8, and after that with JPMS and the open-sourcing of JFR, it has been removed. I can only find references to that So it seems to me that somehow, when Cryostat connects to your application, it thinks that it's talking to a JDK version older than 8u242, which cannot be the case. I think this |
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got it, if it helps is how jdks is build, flags are as above and additional args. Is there something on my end what I can check ? |
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If the check in the second link fails then it will indeed fall back to trying to use V1, which is incorrect and would lead to the It looks like these two classes and respective modules might be the ones needed to get JFR V2 detection to work. Maybe adding |
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@andrewazores yes, it worked finally , thanks ! On the opposite side, documentation for this is missing on cryostat page, I was following it and according to description it just worked. I probably will open some github issues when I came up with some minimal setup and ask to add this to website. On other notice, adding some better detection of this situation and showing proper dialog message will much definetely improve user experience. again, thanks for help ! Appreciated ! |
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created https://github.com/cryostatio/cryostat/issues/615 for improving docs |
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created #616 for error handling improvement for better UX |
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@grzesuav perfect, yes if you can figure out the minimal set of modules required it would be really great to add this to the documentation. As far as I know you're probably the only person who has really tested this is any depth so far :-) I think detecting this particular case might be difficult because the failure happens deep in the call stack in third party code, but I'll try to think of some other way that we can add some troubleshooting UI to help expose these kinds of problems. I'm thinking that even some view that check for the existence/availability of particular MXBeans would have been useful in a case like this, so that even if the error messages that appear are still generic and vague, at least we have some built-in tools to try to diagnose these failures without having to dive through logs, stack traces, and third party source code. |
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Looking at cryostat logs, I see few errors like below, my application does not have cryostat agents - I though it is used only for discovery - does the agent is required to actually start recording ? |
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No, the Cryostat Agent is not needed here. Any features in the Cryostat UI can be used with the Cryostat Agent, or with a simple JMX setup like you are doing here. The Agent these logs are talking about is the JMC Agent, which is used for the Events > Probe Templates view only. You can safely ignore these log messages. |
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https://github.com/openjdk/jmc/blob/4c9d9e47bcf13d6c12ddfcdeddb2e90dbe3b691b/core/org.openjdk.jmc.rjmx.common/src/main/java/org/openjdk/jmc/rjmx/common/services/jfr/internal/FlightRecorderServiceFactory.java#L44
https://github.com/openjdk/jmc/blob/4c9d9e47bcf13d6c12ddfcdeddb2e90dbe3b691b/core/org.openjdk.jmc.rjmx.common/src/main/java/org/openjdk/jmc/rjmx/common/services/jfr/internal/FlightRecorderCommunicationHelperV2.java#L103
If the check in the second link fails then it will indeed fall back to trying to use V1, which is incorrect and would lead to the
com.sun.management.MissionControlclass loading (which will always fail on a modern JDK version - there is no module containing this cl…