Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/15820#discussion_r88758444
--- Diff:
external/kafka-0-10-sql/src/main/scala/org/apache/spark/sql/kafka010/CachedKafkaConsumer.scala
---
@@ -47,40 +51,191 @@ 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.
+ *
+ * When `failOnDataLoss` is `true`, this will either return record at
offset if available, or
+ * throw exception.
+ *
+ * When `failOnDataLoss` is `false`, this will either return record at
offset if available, or
+ * return the next earliest available record less than untilOffset, or
null. It will not throw
+ * any exception.
*/
- 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 must always be less than untilOffset [offset: $offset,
untilOffset: $untilOffset]")
logDebug(s"Get $groupId $topicPartition nextOffset
$nextOffsetInFetchedData requested $offset")
- if (offset != nextOffsetInFetchedData) {
- logInfo(s"Initial fetch for $topicPartition $offset")
- seek(offset)
- poll(pollTimeoutMs)
+ var toFetchOffset = offset
+ while (toFetchOffset != UNKNOWN_OFFSET) {
+ try {
+ val record = fetchData(toFetchOffset, untilOffset, pollTimeoutMs,
failOnDataLoss)
+ if (record == null) {
+ reset()
+ }
+ return record
+ } catch {
+ case e: OffsetOutOfRangeException =>
+ val message =
+ if (failOnDataLoss) {
+ s"Cannot fetch offset $toFetchOffset"
+ } else {
+ s"Cannot fetch offset $toFetchOffset. Some data may be lost.
" +
+ "Recovering from the earliest offset"
+ }
+ reportDataLoss(failOnDataLoss, message, e)
+ toFetchOffset = getNextEarliestOffset(toFetchOffset, untilOffset)
+ }
}
+ reset()
+ null
+ }
- if (!fetchedData.hasNext()) { poll(pollTimeoutMs) }
- assert(fetchedData.hasNext(),
- s"Failed to get records for $groupId $topicPartition $offset " +
- s"after polling for $pollTimeoutMs")
- var record = fetchedData.next()
+ /**
+ * Return the next earliest available offset in [offset, untilOffset).
If all offsets in
+ * [offset, untilOffset) are invalid (e.g., the topic is deleted and
recreated), it will return
+ * `UNKNOWN_OFFSET`.
+ */
+ private def getNextEarliestOffset(offset: Long, untilOffset: Long): Long
= {
+ val (earliestOffset, latestOffset) = getAvailableOffsetRange()
+ if (offset >= latestOffset || earliestOffset >= untilOffset) {
+ // [offset, untilOffset) and [earliestOffset, latestOffset) have no
overlap,
+ // either
+ // --------------------------------------------------------
+ // ^ ^ ^ ^
+ // | | | |
+ // earliestOffset latestOffset offset untilOffset
+ //
+ // or
+ // --------------------------------------------------------
+ // ^ ^ ^ ^
+ // | | | |
+ // offset untilOffset earliestOffset latestOffset
+ val warningMessage =
+ s"""
+ |The current available offset range is [$earliestOffset,
$latestOffset).
+ | Offset ${offset} is out of range, and records in [$offset,
$untilOffset) will be
+ | skipped ${additionalMessage(failOnDataLoss = false)}
+ """.stripMargin
+ logWarning(warningMessage)
+ UNKNOWN_OFFSET
+ } else if (offset >= earliestOffset) {
+ //
-----------------------------------------------------------------------------
+ // ^ ^ ^
^
+ // | | |
|
+ // earliestOffset offset min(untilOffset,latestOffset)
max(untilOffset, latestOffset)
+ //
+ // This will happen when a topic is deleted and recreated, and new
data are pushed very fast,
+ // then we will see `offset` disappears first then appears again.
Although the parameters
+ // are same, the state in Kafka cluster is changed, so the outer
loop won't be endless.
+ logWarning(s"Found a disappeared offset $offset. " +
+ s"Some data may be lost ${additionalMessage(failOnDataLoss =
false)}")
+ offset
+ } else {
+ //
------------------------------------------------------------------------------
+ // ^ ^ ^
^
+ // | | |
|
+ // offset earliestOffset min(untilOffset,latestOffset)
max(untilOffset, latestOffset)
+ val warningMessage =
+ s"""
+ |The current available offset range is [$earliestOffset,
$latestOffset).
+ | Offset ${offset} is out of range, and records in [$offset,
$earliestOffset) will be
+ | skipped ${additionalMessage(failOnDataLoss = false)}
+ """.stripMargin
+ logWarning(warningMessage)
+ earliestOffset
+ }
+ }
- if (record.offset != offset) {
- logInfo(s"Buffer miss for $groupId $topicPartition $offset")
+ /**
+ * Get the earliest record in [offset, untilOffset). If there is not
such record, return null and
+ * clear the fetched data.
+ */
+ private def fetchData(
+ offset: Long,
+ untilOffset: Long,
--- End diff --
untilOffset and failOnDataLoss not really needed.
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