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Posted to issues@flink.apache.org by "Martijn Visser (Jira)" <ji...@apache.org> on 2022/12/08 09:01:00 UTC
[jira] [Commented] (FLINK-30334) SourceCoordinator error splitRequest check cause HybridSource loss of data and hang
[ https://issues.apache.org/jira/browse/FLINK-30334?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17644680#comment-17644680 ]
Martijn Visser commented on FLINK-30334:
----------------------------------------
[~lemonjing] Isn't your second source also a batch/bounded source, while it should be a streaming/unbounded source?
> SourceCoordinator error splitRequest check cause HybridSource loss of data and hang
> -----------------------------------------------------------------------------------
>
> Key: FLINK-30334
> URL: https://issues.apache.org/jira/browse/FLINK-30334
> Project: Flink
> Issue Type: Bug
> Components: Runtime / Coordination
> Affects Versions: 1.16.0, 1.17.0
> Reporter: Ran Tao
> Priority: Critical
> Labels: pull-request-available
>
> If we use hybrid source, for example, filesystem source A read a.csv, filesystem B read b.csv. It's a very simple case, but it will hang in second source with:
> 10802 [SourceCoordinator-Source: hybrid_source[1]] INFO org.apache.flink.runtime.source.coordinator.SourceCoordinator [] - Source Source: hybrid_source[1] received split request from parallel task 0 (#0)
> 10802 [SourceCoordinator-Source: hybrid_source[1]] INFO org.apache.flink.connector.file.src.impl.StaticFileSplitEnumerator [] - Subtask 0 (on host '') is requesting a file source split
> 10803 [SourceCoordinator-Source: hybrid_source[1]] INFO org.apache.flink.connector.file.src.assigners.LocalityAwareSplitAssigner [] - Assigning split to non-localized request: Optional[FileSourceSplit: [file:/Users/xxx/a.csv|file:///Users/xxx/a.csv] [0, 49) (no host info) ID=0000000001 position=null]
> 10808 [SourceCoordinator-Source: hybrid_source[1]] INFO org.apache.flink.connector.file.src.impl.StaticFileSplitEnumerator [] - Assigned split to subtask 0 : FileSourceSplit: [file:/Users/xxx/a.csv|file:///Users/xxx/a.csv] [0, 49) (no host info) ID=0000000001 position=null
> 10816 [Source: hybrid_source[1] -> Sink: print_out[2] (1/1)#0] INFO org.apache.flink.connector.base.source.hybrid.HybridSourceReader [] - Adding splits subtask=0 sourceIndex=0 currentReader=org.apache.flink.connector.file.src.impl.FileSourceReader@1e8e1971 [HybridSourceSplit
> {sourceIndex=0, splitId=0000000001}
> ]
> 10817 [Source: hybrid_source[1] -> Sink: print_out[2] (1/1)#0] INFO org.apache.flink.connector.base.source.reader.SourceReaderBase [] - Adding split(s) to reader: [FileSourceSplit: [file:/Users/xxx/a.csv|file:///Users/chucheng/TMP/a.csv] [0, 49) (no host info) ID=0000000001 position=null]
> 10822 [Source Data Fetcher for Source: hybrid_source[1] -> Sink: print_out[2] (1/1)#0] INFO org.apache.flink.connector.base.source.reader.fetcher.SplitFetcher [] - Starting split fetcher 0
> 10864 [Source Data Fetcher for Source: hybrid_source[1] -> Sink: print_out[2] (1/1)#0] INFO org.apache.flink.connector.base.source.reader.fetcher.SplitFetcher [] - Finished reading from splits [0000000001]
> +I[hello_a, flink, 1]
> +I[hello_a, hadoop, 2]
> +I[hello_a, world, 3]
> 10866 [Source: hybrid_source[1] -> Sink: print_out[2] (1/1)#0] INFO org.apache.flink.connector.base.source.reader.SourceReaderBase [] - Finished reading split(s) [0000000001]
> 10868 [Source: hybrid_source[1] -> Sink: print_out[2] (1/1)#0] INFO org.apache.flink.connector.base.source.reader.fetcher.SplitFetcherManager [] - Closing splitFetcher 0 because it is idle.
> 10868 [Source: hybrid_source[1] -> Sink: print_out[2] (1/1)#0] INFO org.apache.flink.connector.base.source.reader.fetcher.SplitFetcher [] - Shutting down split fetcher 0
> 10868 [Source Data Fetcher for Source: hybrid_source[1] -> Sink: print_out[2] (1/1)#0] INFO org.apache.flink.connector.base.source.reader.fetcher.SplitFetcher [] - Split fetcher 0 exited.
> 10869 [SourceCoordinator-Source: hybrid_source[1]] INFO org.apache.flink.runtime.source.coordinator.SourceCoordinator [] - Source Source: hybrid_source[1] received split request from parallel task 0 (#0)
> 10870 [SourceCoordinator-Source: hybrid_source[1]] INFO org.apache.flink.connector.file.src.impl.StaticFileSplitEnumerator [] - Subtask 0 (on host '') is requesting a file source split
> 10872 [SourceCoordinator-Source: hybrid_source[1]] INFO org.apache.flink.connector.file.src.impl.StaticFileSplitEnumerator [] - No more splits available for subtask 0
> 10872 [Source: hybrid_source[1] -> Sink: print_out[2] (1/1)#0] INFO org.apache.flink.connector.base.source.reader.SourceReaderBase [] - Reader received NoMoreSplits event.
> 10872 [Source: hybrid_source[1] -> Sink: print_out[2] (1/1)#0] INFO org.apache.flink.connector.base.source.hybrid.HybridSourceReader [] - End of input subtask=0 sourceIndex=0 org.apache.flink.connector.file.src.impl.FileSourceReader@1e8e1971
> StaticFileSplitEnumerator:org.apache.flink.connector.file.src.impl.StaticFileSplitEnumerator@69906bb9
> 10874 [SourceCoordinator-Source: hybrid_source[1]] INFO org.apache.flink.connector.base.source.hybrid.HybridSourceSplitEnumerator [] - Starting enumerator for sourceIndex=1
> 10879 [Source: hybrid_source[1] -> Sink: print_out[2] (1/1)#0] INFO org.apache.flink.connector.base.source.hybrid.HybridSourceReader [] - Switch source event: subtask=0 sourceIndex=1 source=org.apache.flink.connector.file.src.FileSource@12ef574f
> 10879 [Source: hybrid_source[1] -> Sink: print_out[2] (1/1)#0] INFO org.apache.flink.connector.base.source.reader.SourceReaderBase [] - Closing Source Reader.
> 10882 [SourceCoordinator-Source: hybrid_source[1]] INFO org.apache.flink.runtime.source.coordinator.SourceCoordinator [] - Source Source: hybrid_source[1] received split request from parallel task 0 (#0)
> *do not read next source data and hang at 'received split request from parallel task'*
>
> The reason is that in the 1.16 & master, latest code add context.hasNoMoreSplits check then call enumerator.handleSplitRequest. We do understand the comments for reducing the call splits. But it not consider the the situation about HybridSource. When a subtask hasNoMoreSplits, it will switch to next source. But here just set a check without this situation. When first source read finish, the context just let this subtask with noMoreSplit Status. And the later check can't assign splits with next sources. However , the flink 1.15 is correct.
>
> *SourceCoordinator*
>
> {code:java}
> private void handleRequestSplitEvent(int subtask, int attemptNumber, RequestSplitEvent event) {
> LOG.info(
> "Source {} received split request from parallel task {} (#{})",
> operatorName,
> subtask,
> attemptNumber);
> // request splits from the enumerator only if the enumerator has un-assigned splits
> // this helps to reduce unnecessary split requests to the enumerator
> if (!context.hasNoMoreSplits(subtask)) {
> enumerator.handleSplitRequest(subtask, event.hostName());
> }
> } {code}
> SourceCoordinator call `context.hasNoMoreSplits` check cause the subtask not read the other child sources in hybrid source.
>
> SourceCoordinatorContext
>
> {code:java}
> boolean hasNoMoreSplits(int subtaskIndex) { return subtaskHasNoMoreSplits[subtaskIndex]; }
> @Override
> public void signalNoMoreSplits(int subtask) {
> checkSubtaskIndex(subtask);
> // Ensure the split assignment is done by the coordinator executor.
> callInCoordinatorThread(
> () -> {
> subtaskHasNoMoreSplits[subtask] = true;
> signalNoMoreSplitsToAttempts(subtask);
> return null; // void return value
> },
> "Failed to send 'NoMoreSplits' to reader " + subtask);
> }
> {code}
> context set subtask noMoreSplit is true if source is done (without considering the hybrid situation).
>
>
> 1.15
>
> {code:java}
> public void handleEventFromOperator(int subtask, OperatorEvent event) {
> runInEventLoop(
> () -> {
> if (event instanceof RequestSplitEvent) {
> LOG.info(
> "Source {} received split request from parallel task {}",
> operatorName,
> subtask);
> enumerator.handleSplitRequest(
> subtask, ((RequestSplitEvent) event).hostName());
> } {code}
>
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