Github user tillrohrmann commented on a diff in the pull request: https://github.com/apache/flink/pull/3278#discussion_r100030073 --- Diff: flink-connectors/flink-connector-kafka-base/src/test/java/org/apache/flink/streaming/connectors/kafka/FlinkKafkaProducerBaseTest.java --- @@ -293,6 +293,61 @@ public void run() { testHarness.close(); } + /** + * This test is meant to assure that testAtLeastOnceProducer is valid by testing that if flushing is disabled, + * the snapshot method does indeed finishes without waiting for pending records; + * we set a timeout because the test will not finish if the logic is broken + */ + @Test(timeout=5000) + public void testDoesNotWaitForPendingRecordsIfFlushingDisabled() throws Throwable { + final OneShotLatch inputLatch = new OneShotLatch(); + + final DummyFlinkKafkaProducer<String> producer = new DummyFlinkKafkaProducer<>( + FakeStandardProducerConfig.get(), null, inputLatch, 100, new AtomicBoolean(false)); + producer.setFlushOnCheckpoint(false); + + final OneInputStreamOperatorTestHarness<String, Object> testHarness = + new OneInputStreamOperatorTestHarness<>(new StreamSink(producer)); + + testHarness.open(); + + List<Callback> pending = producer.getProducerInstance().getPending(); + + for (int i = 0; i < 100; i++) { + testHarness.processElement(new StreamRecord<>("msg-" + i)); + } + + inputLatch.await(); --- End diff -- There is no concurrency in this test. Thus no need to synchronize on anything. The moment you reach this point, `inputLatch` will be triggered.
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