Fix the consumer race in spring-kafka-2.3.x-scenario

The scenario consumer has no committed offset and starts from the latest
offset, while healthCheck reported success as soon as Tomcat started. When the
health check hit right after startup, the entry request sent "helloWorld"
before the consumer got its partition, so the consumer skipped it, the
request waited forever on the latch and its segment was never reported
(SegmentNotFoundException for GET:/case/spring-kafka-case). On ubuntu-26.04
runners spring-kafka 2.7.14 lost this race on every attempt.

Report healthy only after partitions are assigned, the same way
kafka-scenario does.

Author: wu-sheng

test/plugin/scenarios/spring-kafka-2.3.x-scenario/src/main/java/test/apache/skywalking/apm/testcase/spring/kafka/controller/CaseController.java

@@ -22,8 +22,10 @@
 import okhttp3.Request;
 import okhttp3.Response;
 import org.apache.kafka.clients.consumer.ConsumerConfig;
+import org.apache.kafka.clients.consumer.ConsumerRebalanceListener;
 import org.apache.kafka.clients.consumer.ConsumerRecord;
 import org.apache.kafka.clients.producer.ProducerConfig;
+import org.apache.kafka.common.TopicPartition;
 import org.apache.kafka.common.serialization.Deserializer;
 import org.apache.kafka.common.serialization.StringDeserializer;
 import org.apache.kafka.common.serialization.StringSerializer;
@@ -43,6 +45,7 @@
 import javax.annotation.PostConstruct;
 import java.util.Arrays;
 import java.io.IOException;
+import java.util.Collection;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.concurrent.CountDownLatch;
@@ -62,6 +65,7 @@ public class CaseController {
 
     private CountDownLatch latch;
     private String helloWorld = "helloWorld";
+    private volatile boolean partitionsAssigned = false;
 
     @PostConstruct
     private void setUp() {
@@ -108,6 +112,19 @@ private void setUpConsumer() {
         Deserializer<String> stringDeserializer = new StringDeserializer();
         DefaultKafkaConsumerFactory<String, String> factory = new DefaultKafkaConsumerFactory(configs, stringDeserializer, stringDeserializer);
         ContainerProperties props = new ContainerProperties(topicName);
+        // The consumer starts from the latest offset, so the case must not send before partitions are assigned.
+        props.setConsumerRebalanceListener(new ConsumerRebalanceListener() {
+            @Override
+            public void onPartitionsRevoked(Collection<TopicPartition> partitions) {
+            }
+
+            @Override
+            public void onPartitionsAssigned(Collection<TopicPartition> partitions) {
+                if (!partitions.isEmpty()) {
+                    partitionsAssigned = true;
+                }
+            }
+        });
         props.setMessageListener(new AcknowledgingMessageListener<String, String>() {
             @Override
             public void onMessage(ConsumerRecord<String, String> data, Acknowledgment acknowledgment) {
@@ -153,7 +170,10 @@ public String springKafkaConsumerPing() {
     @RequestMapping("/healthCheck")
     @ResponseBody
     public String healthCheck() {
-        return SUCCESS;
+        if (partitionsAssigned) {
+            return SUCCESS;
+        }
+        throw new RuntimeException("kafka consumer partitions not assigned");
     }
 }