philipnee commented on code in PR #14920:
URL: https://github.com/apache/kafka/pull/14920#discussion_r1416732684


##########
clients/src/main/java/org/apache/kafka/clients/consumer/internals/AsyncKafkaConsumer.java:
##########
@@ -957,6 +966,57 @@ private void close(Duration timeout, boolean 
swallowException) {
         }
     }
 
+    /**
+     * Prior to closing the network thread, we need to make sure the following 
operations happen in the right sequence:
+     * 1. autocommit offsets
+     * 2. revoke all partitions
+     */
+    private void prepareShutdown(final Timer timer) {
+        if (!groupMetadata.isPresent())
+            return;
+
+        maybeAutoCommitSync(timer);
+        timer.update();
+        if (!subscriptions.hasAutoAssignedPartitions() || 
subscriptions.assignedPartitions().isEmpty())
+            return;
+
+        try {
+            // If the consumer is in a group, we will pause and revoke all 
assigned partitions
+            onLeavePrepare().get(timer.remainingMs(), TimeUnit.MILLISECONDS);
+            timer.update();
+        } catch (Exception e) {
+            Exception exception = e;
+            if (e instanceof ExecutionException)
+                exception = (Exception) e.getCause();
+            throw new KafkaException("User rebalance callback throws an 
error", exception);
+        } finally {
+            subscriptions.assignFromSubscribed(Collections.emptySet());
+        }
+    }
+
+    private void maybeAutoCommitSync(final Timer timer) {
+        if (autoCommitEnabled) {
+            Map<TopicPartition, OffsetAndMetadata> allConsumed = 
subscriptions.allConsumed();
+            try {
+                log.debug("Sending synchronous auto-commit of offsets {} on 
closing", allConsumed);
+                commitSync(allConsumed, 
Duration.ofMillis(timer.remainingMs()));
+            } catch (Exception e) {
+                // consistent with async auto-commit failures, we do not 
propagate the exception
+                log.warn("Synchronous auto-commit of offsets {} failed: {}", 
allConsumed, e.getMessage());
+            }
+        }
+    }
+
+    private CompletableFuture<Void> onLeavePrepare() {
+        SortedSet<TopicPartition> droppedPartitions = new 
TreeSet<>(MembershipManagerImpl.TOPIC_PARTITION_COMPARATOR);
+        droppedPartitions.addAll(subscriptions.assignedPartitions());
+        if (!subscriptions.hasAutoAssignedPartitions() || 
droppedPartitions.isEmpty()) {
+            return CompletableFuture.completedFuture(null);
+        }
+        // TODO: Invoke rebalanceListener via KAFKA-15276
+        return CompletableFuture.completedFuture(null);
+    }
+

Review Comment:
   Thanks.  I mostly agree with your idea. Though - I think simply firing the 
callback revocation from the close() should be enough - but I think sending 
leave-group and closing events as you suggested is a good idea.



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