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Posted to issues@flink.apache.org by "Piotr Nowojski (JIRA)" <ji...@apache.org> on 2019/07/02 16:21:00 UTC
[jira] [Updated] (FLINK-13063) AsyncWaitOperator can loose data
during checkpointing
[ https://issues.apache.org/jira/browse/FLINK-13063?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Piotr Nowojski updated FLINK-13063:
-----------------------------------
Description:
For the following setup of chained operators:
{noformat}
SourceOperator -> FlatMap -> AsyncOperator{noformat}
Lets assume that input buffer of {{AsyncOperator}} is full. We start processing a record from the {{SourceOperator}}, we pass it to the {{FlatMap}}, which fan it out (multiplies it 10 times). First multiplied record reaches {{AsyncOperator}} and is special treated (stored in {{AsyncWaitOperator#pendingStreamElementQueueEntry}} ) and then {{AsyncWaitOperator}} waits (and releases) on the checkpoint lock (in {{AsyncWaitOperator#addAsyncBufferEntry}} . If a checkpoint is triggered now, both {{SourceOperator}} and {{FlatMap}} will be checkpointed assumed that all of those 10 multiplied records were processed, which is not true. Only the first one is checkpointed by the {{AsyncWatiOperator}}. Remaining 9 are not. So if we ever restore state from this checkpoint, we have lost those 9 records.
Similar issue (I think previously known) can happen if for example some upstream operator to the {{AsyncOperator}} fires a processing time timer, that emits some data. But in that case, {{AsyncWaitOperator#pendingStreamElementQueueEntry}} is being overwritten.
CC [~aljoscha] [~StephanEwen] [~srichter]
was:
For the following setup of chained operators:
{noformat}
SourceOperator -> FlatMap -> AsyncOperator{noformat}
Lets assume that input buffer of {{AsyncOperator}} is full. We start processing a record from the {{SourceOperator}}, we pass it to the {{FlatMap}}, which fan it out (multiplies it 10 times). First multiplied record reaches {{AsyncOperator}} and is special treated (stored in {{AsyncWaitOperator#pendingStreamElementQueueEntry}} ) and then {{AsyncWaitOperator}} waits (and releases) on the checkpoint lock (in {{AsyncWaitOperator#addAsyncBufferEntry}} . If a checkpoint is triggered now, both {{SourceOperator}} and {{FlatMap}} will be checkpointed assumed that all of those 10 multiplied records were processed, which is not true. Only the first one is checkpointed by the {{AsyncWatiOperator}}. Remaining 9 are not. So if we ever restore state from this checkpoint, we have lost those 9 records.
CC [~aljoscha] [~StephanEwen] [~srichter]
> AsyncWaitOperator can loose data during checkpointing
> -----------------------------------------------------
>
> Key: FLINK-13063
> URL: https://issues.apache.org/jira/browse/FLINK-13063
> Project: Flink
> Issue Type: Bug
> Components: API / DataStream
> Affects Versions: 1.6.4, 1.7.2, 1.8.1, 1.9.0
> Reporter: Piotr Nowojski
> Assignee: Piotr Nowojski
> Priority: Critical
>
> For the following setup of chained operators:
> {noformat}
> SourceOperator -> FlatMap -> AsyncOperator{noformat}
> Lets assume that input buffer of {{AsyncOperator}} is full. We start processing a record from the {{SourceOperator}}, we pass it to the {{FlatMap}}, which fan it out (multiplies it 10 times). First multiplied record reaches {{AsyncOperator}} and is special treated (stored in {{AsyncWaitOperator#pendingStreamElementQueueEntry}} ) and then {{AsyncWaitOperator}} waits (and releases) on the checkpoint lock (in {{AsyncWaitOperator#addAsyncBufferEntry}} . If a checkpoint is triggered now, both {{SourceOperator}} and {{FlatMap}} will be checkpointed assumed that all of those 10 multiplied records were processed, which is not true. Only the first one is checkpointed by the {{AsyncWatiOperator}}. Remaining 9 are not. So if we ever restore state from this checkpoint, we have lost those 9 records.
> Similar issue (I think previously known) can happen if for example some upstream operator to the {{AsyncOperator}} fires a processing time timer, that emits some data. But in that case, {{AsyncWaitOperator#pendingStreamElementQueueEntry}} is being overwritten.
> CC [~aljoscha] [~StephanEwen] [~srichter]
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