Github user tdas commented on a diff in the pull request: https://github.com/apache/spark/pull/22042#discussion_r209477156 --- Diff: external/kafka-0-10-sql/src/main/scala/org/apache/spark/sql/kafka010/KafkaDataConsumer.scala --- @@ -251,32 +274,53 @@ private[kafka010] case class InternalKafkaConsumer( untilOffset: Long, pollTimeoutMs: Long, failOnDataLoss: Boolean): ConsumerRecord[Array[Byte], Array[Byte]] = { - if (offset != nextOffsetInFetchedData || !fetchedData.hasNext()) { - // This is the first fetch, or the last pre-fetched data has been drained. + if (offset != nextOffsetInFetchedData) { + // This is the first fetch, or the fetched data has been reset. // Seek to the offset because we may call seekToBeginning or seekToEnd before this. seek(offset) poll(pollTimeoutMs) + } else if (!fetchedData.hasNext) { + // The last pre-fetched data has been drained. + if (offset < offsetAfterPoll) { + // Offsets in [offset, offsetAfterPoll) are missing. We should skip them. + resetFetchedData() + throw new MissingOffsetException(offset, offsetAfterPoll) + } else { + seek(offset) + poll(pollTimeoutMs) + } } if (!fetchedData.hasNext()) { - // We cannot fetch anything after `poll`. Two possible cases: + // We cannot fetch anything after `poll`. Three possible cases: // - `offset` is out of range so that Kafka returns nothing. Just throw // `OffsetOutOfRangeException` to let the caller handle it. // - Cannot fetch any data before timeout. TimeoutException will be thrown. + // - Fetched something but all of them are not valid date messages. In this case, the position + // will be changed and we can use it to determine this case. val range = getAvailableOffsetRange() if (offset < range.earliest || offset >= range.latest) { throw new OffsetOutOfRangeException( Map(topicPartition -> java.lang.Long.valueOf(offset)).asJava) - } else { + } else if (offsetBeforePoll == offsetAfterPoll) { --- End diff -- Just to be clear, can this happen only if there is a timeout?? And if so then why push this condition and exception into the poll() method thus simplifying this method?
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