yaojingguo opened a new issue #6456:
URL: https://github.com/apache/skywalking/issues/6456
Please answer these questions before submitting your issue.
- Why do you submit this issue?
- [ ] Question or discussion
- [x] Bug
- [ ] Requirement
- [ ] Feature or performance improvement
___
### Bug
- Which version of SkyWalking, OS, and JRE?
SkyWalking：v8.4.0, OS: CentOS Linux release 7.4.1708 (Core), JRE: 1.8.0_191,
spring-kafka 2.2.6.RELEASE
- Which company or project?
- What happened?
My code uses KafkaTemplate to send messages to Kafka. The following usages
of KafkaTemplate are used to send messages.
```java
// Without callback
template.send(topic, msg);
// With callback
template.execute(
(Producer<String, String> producer) -> {
producer.send(
new ProducerRecord<>(topic, msg),
(RecordMetadata metadata, Exception e) -> {
if (e != null) {
System.out.println("message sending failed");
} else {
System.out.println("message sending succeeded");
}
});
return 0;
});
```
agent/logs/skywalking-api.log has the following exception:
```
ERROR 2021-02-25 20:36:23:117 kafka-producer-network-thread | producer-2
InstMethodsInter : class[class
org.apache.kafka.clients.producer.KafkaProducer$InterceptorCallback] before
method[onCompletion] intercept failure
java.lang.ClassCastException:
org.apache.skywalking.apm.plugin.kafka.CallbackAdapterInterceptor cannot be
cast to
org.apache.skywalking.apm.agent.core.plugin.interceptor.enhance.EnhancedInstance
at
org.apache.skywalking.apm.plugin.kafka.CallbackInterceptor.getSnapshot(CallbackInterceptor.java:83)
at
org.apache.skywalking.apm.plugin.kafka.CallbackInterceptor.beforeMethod(CallbackInterceptor.java:44)
at
org.apache.skywalking.apm.agent.core.plugin.interceptor.enhance.InstMethodsInter.intercept(InstMethodsInter.java:76)
at
org.apache.kafka.clients.producer.KafkaProducer$InterceptorCallback.onCompletion(KafkaProducer.java)
at
org.apache.kafka.clients.producer.internals.ProducerBatch.completeFutureAndFireCallbacks(ProducerBatch.java:201)
at
org.apache.kafka.clients.producer.internals.ProducerBatch.done(ProducerBatch.java:187)
at
org.apache.kafka.clients.producer.internals.Sender.completeBatch(Sender.java:599)
at
org.apache.kafka.clients.producer.internals.Sender.completeBatch(Sender.java:575)
at
org.apache.kafka.clients.producer.internals.Sender.handleProduceResponse(Sender.java:485)
at
org.apache.kafka.clients.producer.internals.Sender.access$100(Sender.java:74)
at
org.apache.kafka.clients.producer.internals.Sender$1.onComplete(Sender.java:700)
at
org.apache.kafka.clients.ClientResponse.onComplete(ClientResponse.java:109)
at
org.apache.kafka.clients.NetworkClient.completeResponses(NetworkClient.java:532)
at org.apache.kafka.clients.NetworkClient.poll(NetworkClient.java:524)
at org.apache.kafka.clients.producer.internals.Sender.run(Sender.java:239)
at org.apache.kafka.clients.producer.internals.Sender.run(Sender.java:163)
at java.lang.Thread.run(Thread.java:748)
```
___
### Possible fix
My guess is that the following branch of
`KafkaProducerInterceptor.beforeMethod`' executed:
```java
} else if (shouldCallbackInstance instanceof Callback) {
Callback callback = (Callback) shouldCallbackInstance;
ContextSnapshot snapshot = ContextManager.capture();
if (null != snapshot) {
CallbackCache cache = new CallbackCache();
cache.setSnapshot(snapshot);
cache.setCallback(callback);
allArguments[1] = new CallbackAdapterInterceptor(cache);
}
}
```
So when `CallbackInterceptor.getSnapshot` tried to cast cache.getCallback()
to EnhancedInstance, a ClassCastException was thrown. One possible fix is to
add a type check to CallbackConstructorInterceptor.onConstruct.
```java
@Override
public void onConstruct(EnhancedInstance objInst, Object[] allArguments)
{
Callback callback = (Callback) allArguments[0];
if (callback instanceof EnhancedInstance) {
CallbackCache cache;
if (null != objInst.getSkyWalkingDynamicField()) {
cache = (CallbackCache) objInst.getSkyWalkingDynamicField();
} else {
cache = new CallbackCache();
}
cache.setCallback(callback);
objInst.setSkyWalkingDynamicField(cache);
}
}
```
If some committers can give me some guidance, I will try to fix this issue.
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