Github user tzulitai commented on a diff in the pull request:
https://github.com/apache/flink/pull/2789#discussion_r87621606
--- Diff:
flink-streaming-connectors/flink-connector-kafka-0.9/src/main/java/org/apache/flink/streaming/connectors/kafka/internal/Handover.java
---
@@ -0,0 +1,136 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.streaming.connectors.kafka.internal;
+
+import org.apache.flink.annotation.VisibleForTesting;
+import org.apache.flink.util.ExceptionUtils;
+import org.apache.kafka.clients.consumer.ConsumerRecords;
+
+import javax.annotation.Nonnull;
+import java.io.Closeable;
+
+import static org.apache.flink.util.Preconditions.checkNotNull;
+
+public final class Handover implements Closeable {
+
+ private final Object lock = new Object();
+
+ private ConsumerRecords<byte[], byte[]> next;
+ private Throwable error;
+ private boolean wakeup;
+
+ @Nonnull
+ public ConsumerRecords<byte[], byte[]> pollNext() throws Exception {
+ synchronized (lock) {
+ while (next == null && error == null) {
+ lock.wait();
+ }
+
+ ConsumerRecords<byte[], byte[]> n = next;
+ if (n != null) {
+ next = null;
+ lock.notifyAll();
+ return n;
+ }
+ else {
+ ExceptionUtils.rethrowException(error,
error.getMessage());
+
+ // this statement cannot be reached since the
above method always throws an exception
+ // this is only here to silence the compiler
and any warnings
+ return ConsumerRecords.empty();
+ }
+ }
+ }
+
+ public void produce(final ConsumerRecords<byte[], byte[]> element)
+ throws InterruptedException, WakeupException,
ClosedException {
+
+ checkNotNull(element);
+
+ synchronized (lock) {
+ while (next != null && !wakeup) {
+ lock.wait();
+ }
+
+ wakeup = false;
+
+ // if there is still an element, we must have been
woken up
+ if (next != null) {
+ throw new WakeupException();
+ }
+ // if there is no error, then this is open and can
accept this element
+ else if (error == null) {
+ next = element;
+ lock.notifyAll();
+ }
+ // an error marks this as closed for the producer
+ else {
+ throw new ClosedException();
+ }
+ }
+ }
+
+ public void reportError(Throwable t) {
+ checkNotNull(t);
+
+ synchronized (lock) {
+ // do not override the initial exception
+ if (error == null) {
+ error = t;
+ }
+ next = null;
+ lock.notifyAll();
+ }
+ }
+
+ @Override
+ public void close() {
+ synchronized (lock) {
+ next = null;
+ wakeup = false;
+
+ if (error == null) {
+ error = new ClosedException();
+ }
+ lock.notifyAll();
+ }
+ }
+
+ public void wakeupProducer() {
+ synchronized (lock) {
+ wakeup = true;
+ lock.notifyAll();
+ }
+ }
+
+ @VisibleForTesting
+ Object getLock() {
--- End diff --
This method doesn't seem to be used, even in the tests.
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