Improving JFR support

[jovanstevanovic]

This PR tries to solve multiple problems in current JFR support.

First, it introduces support for Thread and ThreadGroup repositories.

Before:

  <struct name="eventThread" xsi:nil="true"/>

After:

  <struct name="eventThread">
    <value name="osName">main</value>
    <value name="osThreadId">1</value>
    <value name="javaName">main</value>
    <value name="javaThreadId">1</value>
    <struct name="group">
      <struct name="parent">
        <struct name="parent" xsi:nil="true"/>
        <value name="name">system</value>
      </struct>
      <value name="name">main</value>
    </struct>
  </struct>

Second, it is trying to solve a problem with a bad event signature. For example:

@name("jdk.OSInformation")
@Label("OS Information")
@category("Operating System")
@name("jdk.OSInformation")
class OSInformation extends jdk.jfr.Event {
@Label("Start Time")
@timestamp("TICKS")
long startTime;

@Label("Duration")
@timespan("TICKS")
long duration;

@Label("Event Thread")
@description("Thread in which event was committed in")
Thread eventThread;

@Label("Stack Trace")
@description("Stack Trace starting from the method the event was committed in")
StackTrace stackTrace;

@Label("OS Version")
String osVersion;
}

This is a signature of OSInformation on SVM. In order to make this event work, it should have the same signature as the event on JVM (below).

@name("jdk.OSInformation")
@category("Operating System")
@Label("OS Information")
class OSInformation extends jdk.jfr.Event {
@Label("Start Time")
@timestamp("TICKS")
long startTime;

@Label("OS Version")
String osVersion;
}

[graalvmbot]

Hello jovanstevanovic, thanks for contributing a PR to our project!

We use the Oracle Contributor Agreement to make the copyright of contributions clear. We don't have a record of you having signed this yet, based on your email address jovan -(dot)- stevanovic1 -(at)- outlook -(dot)- com. You can sign it at that link.

If you think you've already signed it, please comment below and we'll check.

[jovanstevanovic]

/signed

[vjovanov]

LGTM, but I think @christianhaeubl would be a better choice to review here.

[jiekang]

Looks to run fine now. Thanks Jovan! I think a review + approval from @christianhaeubl is also appropriate.

[graalvmbot]

jovanstevanovic has signed the Oracle Contributor Agreement (based on email address jovan -(dot)- stevanovic1 -(at)- outlook -(dot)- com) so can contribute to this repository.

[christianhaeubl]

Thanks for working on that. However, the current approach won't work for the following reasons:

• It is not always safe to access the heap allocated Thread object (see one of my comments in the source code).
• At the moment, you are storing Java heap objects into native memory. This will cause crashes.

[christianhaeubl]

@jovanstevanovic: just to let you know, I am currently doing a few final cleanups and then I will merge the changes of this PR to master.

[jovanstevanovic]

@jovanstevanovic: just to let you know, I am currently doing a few final cleanups and then I will merge the changes of this PR to master.

Great! Thanks a lot! 💯

[christianhaeubl]

@jovanstevanovic : could you add a few test cases for this feature? I also fixed a couple bugs as part of my cleanup, so you probably want to wait until the final version is merged.

[jovanstevanovic]

@jovanstevanovic : could you add a few test cases for this feature? I also fixed a couple bugs as part of my cleanup, so you probably want to wait until the final version is merged.

No problem, I can add a few test cases.