[FLINK-22424] Writing to already released buffers potentially causing data corruption during job failover/cancellation

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 1.6.4, 1.7.2, 1.8.3, 1.9.3, 1.10.3, 1.11.3, 1.12.2, 1.13.0
• Fix Version/s: 1.11.4, 1.14.0, 1.13.1, 1.12.4
• Component/s: Runtime / Network
• Labels: pull-request-available
• Assignee: Piotr Nowojski
• Reporter: Piotr Nowojski
• Created: 23/Apr/21 07:38
• Updated: 28/May/21 11:06
• Resolved: 30/Apr/21 14:42

Description

I modified the code to not re-use the same memory segments, but on recycling always free up the segment. And what I have observed is a similar problem as reported in FLINK-21181 ticket, but even more severe:

Caused by: java.lang.RuntimeException: segment has been freed
	at org.apache.flink.streaming.runtime.io.RecordWriterOutput.pushToRecordWriter(RecordWriterOutput.java:109)
	at org.apache.flink.streaming.runtime.io.RecordWriterOutput.collect(RecordWriterOutput.java:93)
	at org.apache.flink.streaming.runtime.io.RecordWriterOutput.collect(RecordWriterOutput.java:44)
	at org.apache.flink.streaming.api.operators.CountingOutput.collect(CountingOutput.java:50)
	at org.apache.flink.streaming.api.operators.CountingOutput.collect(CountingOutput.java:28)
	at org.apache.flink.streaming.api.operators.TimestampedCollector.collect(TimestampedCollector.java:50)
	at org.apache.flink.test.checkpointing.UnalignedCheckpointStressITCase$ReEmitAll.process(UnalignedCheckpointStressITCase.java:477)
	at org.apache.flink.test.checkpointing.UnalignedCheckpointStressITCase$ReEmitAll.process(UnalignedCheckpointStressITCase.java:468)
	at org.apache.flink.streaming.runtime.operators.windowing.functions.InternalIterableProcessWindowFunction.process(InternalIterableProcessWindowFunction.java:57)
	at org.apache.flink.streaming.runtime.operators.windowing.functions.InternalIterableProcessWindowFunction.process(InternalIterableProcessWindowFunction.java:32)
	at org.apache.flink.streaming.runtime.operators.windowing.WindowOperator.emitWindowContents(WindowOperator.java:577)
	at org.apache.flink.streaming.runtime.operators.windowing.WindowOperator.onProcessingTime(WindowOperator.java:533)
	at org.apache.flink.streaming.api.operators.InternalTimerServiceImpl.onProcessingTime(InternalTimerServiceImpl.java:284)
	at org.apache.flink.streaming.runtime.tasks.StreamTask.invokeProcessingTimeCallback(StreamTask.java:1395)
	... 11 more
Caused by: java.lang.IllegalStateException: segment has been freed
	at org.apache.flink.core.memory.MemorySegment.put(MemorySegment.java:483)
	at org.apache.flink.core.memory.MemorySegment.put(MemorySegment.java:1398)
	at org.apache.flink.runtime.io.network.buffer.BufferBuilder.append(BufferBuilder.java:100)
	at org.apache.flink.runtime.io.network.buffer.BufferBuilder.appendAndCommit(BufferBuilder.java:82)
	at org.apache.flink.runtime.io.network.partition.BufferWritingResultPartition.appendUnicastDataForNewRecord(BufferWritingResultPartition.java:250)
	at org.apache.flink.runtime.io.network.partition.BufferWritingResultPartition.emitRecord(BufferWritingResultPartition.java:142)
	at org.apache.flink.runtime.io.network.api.writer.RecordWriter.emit(RecordWriter.java:104)
	at org.apache.flink.runtime.io.network.api.writer.ChannelSelectorRecordWriter.emit(ChannelSelectorRecordWriter.java:54)
	at org.apache.flink.streaming.runtime.io.RecordWriterOutput.pushToRecordWriter(RecordWriterOutput.java:107)
	... 24 more

That's happening also during cancellation/job failover. It's failing when trying to write to already `free`'ed up buffer. Without my changes, this code would silently write some data to a buffer that has already been recycled/returned to the pool. If someone else would pick up this buffer, it would easily lead to the data corruption.

As far as I can tell, the exact reason behind this is that the buffer to which timer attempts to write to, has been released from `ResultSubpartition#onConsumedSubpartition`, causing `BufferConsumer` to be closed (which recycles/frees underlying memory segment ), while matching `BufferBuilder` is still being used...

Issue Links

• relates to: FLINK-21181 Buffer pool is destroyed error when outputting data over a timer after cancellation.
• links to: GitHub Pull Request #15734
• links to: GitHub Pull Request #15778