Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/15820#discussion_r88363196
--- Diff:
external/kafka-0-10-sql/src/main/scala/org/apache/spark/sql/kafka010/CachedKafkaConsumer.scala
---
@@ -47,40 +51,229 @@ private[kafka010] case class CachedKafkaConsumer
private(
/** Iterator to the already fetch data */
private var fetchedData =
ju.Collections.emptyIterator[ConsumerRecord[Array[Byte], Array[Byte]]]
- private var nextOffsetInFetchedData = -2L
+ private var nextOffsetInFetchedData = UNKNOWN_OFFSET
/**
* Get the record for the given offset, waiting up to timeout ms if IO
is necessary.
* Sequential forward access will use buffers, but random access will be
horribly inefficient.
+ *
+ * If `failOnDataLoss` is `false`, it will try to get the earliest
record in
+ * `[offset, untilOffset)` when some illegal state happens. Otherwise,
an `IllegalStateException`
+ * will be thrown.
+ *
+ * It returns `null` only when `failOnDataLoss` is `false` and it cannot
fetch any record between
+ * [offset, untilOffset).
*/
- def get(offset: Long, pollTimeoutMs: Long): ConsumerRecord[Array[Byte],
Array[Byte]] = {
+ def get(
+ offset: Long,
+ untilOffset: Long,
+ pollTimeoutMs: Long,
+ failOnDataLoss: Boolean): ConsumerRecord[Array[Byte], Array[Byte]] =
{
+ require(offset < untilOffset, s"offset: $offset, untilOffset:
$untilOffset")
logDebug(s"Get $groupId $topicPartition nextOffset
$nextOffsetInFetchedData requested $offset")
+ try {
+ fetchDataIfNeeded(offset, pollTimeoutMs)
+ getRecordFromFetchedData(offset, untilOffset, failOnDataLoss)
+ } catch {
+ case e: OffsetOutOfRangeException =>
+ val message =
+ if (failOnDataLoss) {
+ s"""Cannot fetch offset $offset. (GroupId: $groupId,
TopicPartition: $topicPartition).
+ | $INSTRUCTION_FOR_FAIL_ON_DATA_LOSS_TRUE""".stripMargin
+ } else {
+ s"""Cannot fetch offset $offset. Some data may be lost.
Recovering from the earliest
+ | offset (GroupId: $groupId, TopicPartition:
$topicPartition).""".stripMargin
+ }
+ reportDataLoss(failOnDataLoss, message, e)
+ advanceToEarliestOffsetAndFetch(offset, untilOffset, pollTimeoutMs)
+ }
+ }
+
+ /**
+ * Check the pre-fetched data with `offset` and try to fetch from Kafka
if they don't match.
+ */
+ private def fetchDataIfNeeded(offset: Long, pollTimeoutMs: Long): Unit =
{
if (offset != nextOffsetInFetchedData) {
logInfo(s"Initial fetch for $topicPartition $offset")
seek(offset)
poll(pollTimeoutMs)
+ } else if (!fetchedData.hasNext()) {
+ // The last pre-fetched data has been drained.
+ // Seek to the offset because we may call seekToBeginning or
seekToEnd before this.
+ seek(offset)
+ poll(pollTimeoutMs)
--- End diff --
Why havent these two cases been merged?
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