Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/4032#discussion_r23366552
--- Diff:
streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceivedBlockTracker.scala
---
@@ -107,8 +107,14 @@ private[streaming] class ReceivedBlockTracker(
lastAllocatedBatchTime = batchTime
allocatedBlocks
} else {
- throw new SparkException(s"Unexpected allocation of blocks, " +
- s"last batch = $lastAllocatedBatchTime, batch time to allocate =
$batchTime ")
+ // This situation occurs when:
+ // 1. WAL is ended with BatchAllocationEvent, but without
BatchCleanupEvent,
+ // possibly processed batch job or half-processed batch job need to
be processed again,
+ // so the batchTime will be equal to lastAllocatedBatchTime.
+ // 2. Slow checkpointing makes recovered batch time older than WAL
recovered
+ // lastAllocatedBatchTime.
+ // This situation will only occurs in recovery time.
+ logWarning(s"Possibly processed batch $batchTime need to be
processed again in WAL recovery")
--- End diff --
i am not sure we even should throw a warning. Warnings are thrown when
something bad may have happened. In this case, if the code reaches here,
nothing bad or unexpected has happened.
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