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https://issues.apache.org/jira/browse/FLINK-28274?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17562419#comment-17562419
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zl commented on FLINK-28274:
----------------------------
-- Does this problem only occur for \{ContinuousFileMonitoringFunction} or also
for the new \{FileSource}
As [~wanglijie95] said, with FLIP-27, FileSource does not need
{{ContinuousFileMonitoringFunction}} to plays the role of SplitEnumerator, so
this problem won't occur for new FileSource.
-- does it also occur with other operators whose parallelism must be 1 ?
>From what I understand, if the max parallelism is not set to 1, it's possible
>that this problem may occur for these operators whose parallelism must be 1.
-- why fix it if it's only occurring in a legacy component ?
The legacy source are still widely used, for example, When reading files with
datastream api, the first thought is to use readFile/readTextFile() methods,
especially for starters. Since the fix work won't take much effort, may be it's
worthy.
> ContinuousFileMonitoringFunction doesn't work with reactive mode
> ----------------------------------------------------------------
>
> Key: FLINK-28274
> URL: https://issues.apache.org/jira/browse/FLINK-28274
> Project: Flink
> Issue Type: Bug
> Components: API / DataStream, Runtime / Coordination
> Affects Versions: 1.16.0
> Reporter: Robert Metzger
> Assignee: zl
> Priority: Major
> Labels: pull-request-available
>
> This issue was first reported in the Flink Slack:
> https://apache-flink.slack.com/archives/C03G7LJTS2G/p1656257678477659
> It seems that reactive mode is changing the parallelism of the
> `ContinuousFileMonitoringFunction`, which is supposed to always run with a
> parallelism of 1.
> This is the error
> {code}
> INITIALIZING to FAILED with failure cause:
> java.lang.IllegalArgumentException: ContinuousFileMonitoringFunction
> retrieved invalid state.
> at
> org.apache.flink.util.Preconditions.checkArgument(Preconditions.java:138)
> {code}
> You can see from the logs that the parallelism is changing on a rescale event:
> {code}
> 2022-06-27 13:38:54,979 | INFO | .executiongraph.ExecutionGraph | Source:
> Custom File Source (1/1) (cbaad20beee908b95c9fe5c34ba76bfa) switched from
> RUNNING to CANCELING.
> 2022-06-27 13:38:55,254 | INFO | .executiongraph.ExecutionGraph | Source:
> Custom File Source (1/1) (cbaad20beee908b95c9fe5c34ba76bfa) switched from
> CANCELING to CANCELED.
> 2022-06-27 13:38:55,657 | INFO | .executiongraph.ExecutionGraph | Source:
> Custom File Source (2/2) (6ceaacbe8d9aa507b0a56c850082da8c) switched from
> DEPLOYING to INITIALIZING.
> 2022-06-27 13:38:55,722 | INFO | .executiongraph.ExecutionGraph | Source:
> Custom File Source (2/2) (6ceaacbe8d9aa507b0a56c850082da8c) switched from
> INITIALIZING to RUNNING.
> 2022-06-27 13:44:54,058 | INFO | .executiongraph.ExecutionGraph | Source:
> Custom File Source (1/2) (665b12194741744d6bba4408a252fa45) switched from
> RUNNING to CANCELING.
> 2022-06-27 13:45:00,825 | INFO | .executiongraph.ExecutionGraph | Source:
> Custom File Source (1/2) (3cc408fd0eb9ddfa97b22f4dfc09d8dc) switched from
> DEPLOYING to INITIALIZING.
> 2022-06-27 13:45:00,826 | INFO | .executiongraph.ExecutionGraph | Source:
> Custom File Source (1/2) (3cc408fd0eb9ddfa97b22f4dfc09d8dc) switched from
> INITIALIZING to RUNNING.
> 2022-06-27 13:45:01,434 | INFO | .executiongraph.ExecutionGraph | Source:
> Custom File Source (2/2) (79338042d84b6458c34760bc85145512) switched from
> DEPLOYING to INITIALIZING.
> 2022-06-27 13:45:02,427 | INFO | .executiongraph.ExecutionGraph | Source:
> Custom File Source (2/2) (79338042d84b6458c34760bc85145512) switched from
> INITIALIZING to RUNNING.
> {code}
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