Index: clients/src/main/java/org/apache/kafka/clients/consumer/KafkaConsumer.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/clients/src/main/java/org/apache/kafka/clients/consumer/KafkaConsumer.java b/clients/src/main/java/org/apache/kafka/clients/consumer/KafkaConsumer.java
--- a/clients/src/main/java/org/apache/kafka/clients/consumer/KafkaConsumer.java	(revision 1874f2388cffa7a1e866cbe4aff8b92c9d953b41)
+++ b/clients/src/main/java/org/apache/kafka/clients/consumer/KafkaConsumer.java	(revision 225eab98d939beb5ce797c9f50af22fc95fb3445)
@@ -1231,8 +1231,11 @@
                 client.maybeTriggerWakeup();
 
                 if (includeMetadataInTimeout) {
-                    // try to update assignment metadata BUT do not need to block on the timer for join group
-                    updateAssignmentMetadataIfNeeded(timer, false);
+                    // try to update assignment metadata BUT restrict blocking for join group to the poll timeout
+                    if (!updateAssignmentMetadataIfNeeded(timer, true)) {
+                        // Assignment update is still in progress - do not return any records as they may become stale when update is completed
+                        return ConsumerRecords.empty();
+                    }
                 } else {
                     while (!updateAssignmentMetadataIfNeeded(time.timer(Long.MAX_VALUE), true)) {
                         log.warn("Still waiting for metadata");