[Bug] okhttp plugin issue

[angjuLin]

Search before asking

• I had searched in the issues and found no similar issues.

Apache SkyWalking Component

OAP server (apache/skywalking)

What happened

After using SkyWalking version 9.2, I get a java.lang.UnsupportedOperationException: class redefinition failed: attempted to change superclass or interfaces exception when trying to trace a method of a class using Arthas. I've searched for similar issues and found a similar problem when using version 8.X. I solved it by adding the parameters -Dskywalking.agent.is_cache_enhanced_class=true and -Dskywalking.agent.class_cache_mode=MEMORY. Because SkyWalking enhances bytecode information dynamically when used with other probes, the names of newly added fields or methods are dynamic. I noticed that the CacheableTransformerDecorator class was removed after version 9.X. I saw in the commit notes that upgrading the byte-buddy version resolved the dynamic enhancement issue, but this doesn't seem to be the case.

First, taking the okhttp3.RealCall enhancement as an example, I used the jad command on arthas to discover that the source code doesn't contain the SkyWalking enhancement logic. Its implementation logic is simply a wrapper around RealCall, with an additional class named okhttp3/RealCall$auxiliary$7KNXUqCR. ​​However, executing the trace okhttp3.RealCall enqueue command on arthas resulted in a java.lang.UnsupportedOperationException: class redefinition failed: attempted to change superclass or interfaces exception. Even my probe retransformed it, resulting in the same exception. I suspect this is a problem.

Secondly, while upgrading byte-buddy resolved the dynamic enhancement issue, I'm also concerned because the generated enhancement class name, such as okhttp3/RealCall$auxiliary$7KNXUqCR, changes with each generation. Does this indicate instability? I've found that retransformation fails for any class with this name, and okhttp3.RealCall is just one example.

What you expected to happen

Classes enhanced with SkyWalking should not be unable to retransform

How to reproduce

Other probes do not work in many classes enhanced by retransform skywalking

Anything else

Are you willing to submit a pull request to fix on your own?

• Yes I am willing to submit a pull request on my own!

Code of Conduct

• I agree to follow this project's Code of Conduct

[angjuLin]

[wu-sheng]

This seems to be an unsupported version error. Have nothing related that. This class maybe should not be changed by the agent, but it was due to version and code changes.

Anyway, the plugin is from global contributors. I moved this here, and wait for others to take a look.

[wu-sheng]

And meanwhile, working with Arthas is always a challenging topic.

[angjuLin]

This isn't just an arthas issue. Our company's probes currently target version 9.X, but many classes can no longer be enhanced using retransform. In version 8.X, this issue can be circumvented by setting the -Dskywalking.agent.is_cache_enhanced_class=true and -Dskywalking.agent.class_cache_mode=MEMORY parameters. I also tried re-adding the CacheableTransformerDecorator implementation, but retransform works fine after adding it. However, issues with SkyWalking's implementation itself arise. For example, when using okhttp's RealCall enhancement, I get this exception, suggesting the packaging has failed. However, I can still see the packaged class using JAD.

[wu-sheng]

I saw arthes in the stack. You should double check.
In most product env, there is no retransfer.

[angjuLin]

ERROR 2025-09-04 10:45:59.337 Thread-13 InstMethodsInter : class[class okhttp3.RealCall] before method[enqueue] intercept failure
java.lang.ClassCastException: io.shulie.soft.argus.demo.OkHttpDemo$2 cannot be cast to org.apache.skywalking.apm.agent.core.plugin.interceptor.enhance.EnhancedInstance
at org.apache.skywalking.apm.plugin.okhttp.common.EnqueueInterceptor.beforeMethod(EnqueueInterceptor.java:39)
at org.apache.skywalking.apm.agent.core.plugin.interceptor.enhance.InstMethodsInter.intercept(InstMethodsInter.java:76)
at okhttp3.RealCall.enqueue(RealCall.java)
at io.shulie.soft.argus.demo.OkHttpDemo.request(OkHttpDemo.java:52)
at io.shulie.soft.argus.demo.OkHttpDemo$1.run(OkHttpDemo.java:26)
at java.lang.Thread.run(Thread.java:745)

ERROR 2025-09-04 10:45:59.340 Thread-13 InstMethodsInter : class[class okhttp3.RealCall] after method[enqueue] intercept failure
java.lang.NullPointerException
at org.apache.skywalking.apm.agent.core.context.ContextManager.stopSpan(ContextManager.java:194)
at org.apache.skywalking.apm.plugin.okhttp.common.EnqueueInterceptor.afterMethod(EnqueueInterceptor.java:59)
at org.apache.skywalking.apm.agent.core.plugin.interceptor.enhance.InstMethodsInter.intercept(InstMethodsInter.java:97)
at okhttp3.RealCall.enqueue(RealCall.java)
at io.shulie.soft.argus.demo.OkHttpDemo.request(OkHttpDemo.java:52)
at io.shulie.soft.argus.demo.OkHttpDemo$1.run(OkHttpDemo.java:26)
at java.lang.Thread.run(Thread.java:745)

[angjuLin]

[arthas@22170]$ jad okhttp3/RealCall$auxiliary$92g3EUdP

ClassLoader:
+-sun.misc.Launcher$AppClassLoader@18b4aac2
+-sun.misc.Launcher$ExtClassLoader@42d80b78

Location:
/Users/angju/.m2/repository/com/squareup/okhttp3/okhttp/3.14.7/okhttp-3.14.7.jar

/*

• Decompiled with CFR.
  */
  package okhttp3;

import java.util.concurrent.Callable;
import okhttp3.Callback;
import okhttp3.RealCall;

class RealCall$auxiliary$92g3EUdP
implements Runnable,
Callable {
private RealCall argument0;
private Callback argument1;

public Object call() throws Exception {
    this.argument0.enqueue$original$kdygHjVD$accessor$w7P0Idt1(this.argument1);
    return null;
}

@Override
public void run() {
    this.argument0.enqueue$original$kdygHjVD$accessor$w7P0Idt1(this.argument1);
}

RealCall$auxiliary$92g3EUdP(RealCall realCall, Callback callback) {
    this.argument0 = realCall;
    this.argument1 = callback;
}

}

[wu-sheng]

The field name makes me feeling, it is changed by bytebuddy as well.

[angjuLin]

Which field of which class are you talking about?

[angjuLin]

After adding CacheableTransformerDecorator back, there is a problem with the enhanced code properties of okhttp3/RealCall$auxiliary$92g3EUdP, and an additional private Callback argument1; parameter

[angjuLin]

I don't understand why this phenomenon occurs. I understand that after I add the CacheableTransformerDecorator back, the subsequent transforms all use the first cache. Is there any difference in the logic of each transform of SkyWalking?

[lujiajing1126]

Could u pls try the latest release, i.e. https://github.com/apache/skywalking-java/releases/tag/v9.5.0

apache/skywalking-java#757 may help.

[angjuLin]

I tried it. I initially thought that using the latest version would solve the problem, but it didn't work.