Remove obsolete offset within range check

Author: sjvanrossum

sdks/java/io/kafka/src/main/java/org/apache/beam/sdk/io/kafka/KafkaUnboundedReader.java

@@ -151,7 +151,6 @@ public boolean start() throws IOException {
   @Override
   public boolean advance() throws IOException {
     /* Read first record (if any). we need to loop here because :
-     *  - (a) some records initially need to be skipped if they are before consumedOffset
      *  - (b) if curBatch is empty, we want to fetch next batch and then advance.
      *  - (c) curBatch is an iterator of iterators. we interleave the records from each.
      *        curBatch.next() might return an empty iterator.
@@ -176,17 +175,6 @@ public boolean advance() throws IOException {
         long expected = pState.nextOffset;
         long offset = rawRecord.offset();
 
-        if (offset < expected) { // -- (a)
-          // this can happen when compression is enabled in Kafka (seems to be fixed in 0.10)
-          // should we check if the offset is way off from consumedOffset (say > 1M)?
-          LOG.warn(
-              "{}: ignoring already consumed offset {} for {}",
-              this,
-              offset,
-              pState.topicPartition);
-          continue;
-        }
-
         // Apply user deserializers. User deserializers might throw, which will be propagated up
         // and 'curRecord' remains unchanged. The runner should close this reader.
         // TODO: write records that can't be deserialized to a "dead-letter" additional output.

sdks/java/io/kafka/src/main/java/org/apache/beam/sdk/io/kafka/ReadFromKafkaDoFn.java

@@ -440,12 +440,9 @@ public ProcessContinuation processElement(
     LOG.info("Creating Kafka consumer for process continuation for {}", kafkaSourceDescriptor);
     try (Consumer<byte[], byte[]> consumer = consumerFactoryFn.apply(updatedConsumerConfig)) {
       consumer.assign(ImmutableList.of(kafkaSourceDescriptor.getTopicPartition()));
-      long startOffset = tracker.currentRestriction().getFrom();
-      long expectedOffset = startOffset;
-      consumer.seek(kafkaSourceDescriptor.getTopicPartition(), startOffset);
+      long expectedOffset = tracker.currentRestriction().getFrom();
+      consumer.seek(kafkaSourceDescriptor.getTopicPartition(), expectedOffset);
       ConsumerRecords<byte[], byte[]> rawRecords = ConsumerRecords.empty();
-      long skippedRecords = 0L;
-      final Stopwatch sw = Stopwatch.createStarted();
 
       while (true) {
         // Fetch the record size accumulator.
@@ -465,36 +462,6 @@ public ProcessContinuation processElement(
           return ProcessContinuation.resume();
         }
         for (ConsumerRecord<byte[], byte[]> rawRecord : rawRecords) {
-          // If the Kafka consumer returns a record with an offset that is already processed
-          // the record can be safely skipped. This is needed because there is a possibility
-          // that the seek() above fails to move the offset to the desired position. In which
-          // case poll() would return records that are already cnsumed.
-          if (rawRecord.offset() < startOffset) {
-            // If the start offset is not reached even after skipping the records for 10 seconds
-            // then the processing is stopped with a backoff to give the Kakfa server some time
-            // catch up.
-            if (sw.elapsed().getSeconds() > 10L) {
-              LOG.error(
-                  "The expected offset ({}) was not reached even after"
-                      + " skipping consumed records for 10 seconds. The offset we could"
-                      + " reach was {}. The processing of this bundle will be attempted"
-                      + " at a later time.",
-                  expectedOffset,
-                  rawRecord.offset());
-              return ProcessContinuation.resume()
-                  .withResumeDelay(org.joda.time.Duration.standardSeconds(10L));
-            }
-            skippedRecords++;
-            continue;
-          }
-          if (skippedRecords > 0L) {
-            LOG.warn(
-                "{} records were skipped due to seek returning an"
-                    + " earlier position than requested position of {}",
-                skippedRecords,
-                expectedOffset);
-            skippedRecords = 0L;
-          }
           if (!tracker.tryClaim(rawRecord.offset())) {
             return ProcessContinuation.stop();
           }

sdks/java/io/kafka/src/test/java/org/apache/beam/sdk/io/kafka/ReadFromKafkaDoFnTest.java

@@ -19,6 +19,7 @@
 
 import static org.apache.beam.sdk.transforms.errorhandling.BadRecordRouter.BAD_RECORD_TAG;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 
 import java.nio.charset.StandardCharsets;
@@ -523,12 +524,9 @@ public void testProcessElementWithEarlierOffset() throws Exception {
         new OffsetRangeTracker(new OffsetRange(startOffset, startOffset + 3));
     KafkaSourceDescriptor descriptor =
         KafkaSourceDescriptor.of(topicPartition, null, null, null, null, null);
-    ProcessContinuation result =
-        dofnInstanceWithBrokenSeek.processElement(descriptor, tracker, null, receiver);
-    assertEquals(ProcessContinuation.stop(), result);
-    assertEquals(
-        createExpectedRecords(descriptor, startOffset, 3, "key", "value"),
-        receiver.getGoodRecords());
+    assertThrows(
+        IllegalArgumentException.class,
+        () -> dofnInstanceWithBrokenSeek.processElement(descriptor, tracker, null, receiver));
   }
 
   @Test