a suggestion to avoid ClassCircularityError

[shichaoyuan]

Due to the use of ThreadLocalRandom in my custom plugin, ClassCircularityError are occasionally triggered.

I found that many agents have related issues:

1. Preload java.util.concurrent.ThreadLocalRandom… DataDog/dd-trace-java#4865
2. Preload AtomicReferenceArray open-telemetry/opentelemetry-java-instrumentation#3315
3. Fix ClassCircularityError when running with security manager open-telemetry/opentelemetry-java-instrumentation#4557
4. work-around ClassCircularityError newrelic/newrelic-java-agent#600
   ...

Since we will use many jdk classes in custom plugins，should we ignore most java.* classes？

[wu-sheng]

Why do we need to worry about something on other projects' sides? I am a little confused.

[shichaoyuan]

Because ClassCircularityError may also be encountered in Skywalking’s agent, if certain jdk classes are used in the plugin.

[wu-sheng]

I don't think this is a big issue. For the worst case, a bootstrap plugin can't be used, which should be tested during contribution review stage.
But excluding them would cause a lot of questions, I don't think I should suffer that noise.

[shichaoyuan]

refer to https://bugs.openjdk.org/browse/JDK-8164165

Class loading may be triggered by user code, which may cause user code to throw ClassCircularityError.

[wu-sheng]

Yes. This statement is correct for sure, and your scenario could happen too. Don't get me wrong, I am not arguing this.

My point is, bootstrap plugin is not activated by default, so, we would not face this by default.
So, that error case should only happen when a bootstrap plugin is acrivated. This is not a big concern for a project or end users, who are adding them by themselves.
But, if we accept your proposals, developers would be very confused why we block things we are not using.

Is this making you more clear?

[shichaoyuan]

Got it, the end user is responsible

[wu-sheng]

We as maintainer would try our best to keep codes as good as possible, to avoid this conflict. But no more on codes level.