[jira] [Commented] (FLINK-17545) Resource leak JDBCUpsertOutputFormat

["Aljoscha Krettek (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-17545?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17107082#comment-17107082 ] 

Aljoscha Krettek commented on FLINK-17545:
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Did you by chance also try this with Flink 1.9? Normally the different UDF methods should not be called concurrently.

> Resource leak JDBCUpsertOutputFormat
> ------------------------------------
>
>                 Key: FLINK-17545
>                 URL: https://issues.apache.org/jira/browse/FLINK-17545
>             Project: Flink
>          Issue Type: Improvement
>          Components: Connectors / JDBC
>    Affects Versions: 1.10.0
>            Reporter: John Lonergan
>            Priority: Major
>
> See also FLINK-17544 for background to this scenario.
> Synchronisation in JDBCUpsertOutputFormat allows resources leaks.
> The close() method is synchronised with write() and flush() but not open.
> So if open() is a slow call (which in my case it occasionally is) then it may not be complete when close() is called.
> In this situation the open() method will eventually proceed to open resources such as database connections that will never be closed by the program.
> So if we are +not+ going to synchronise open() with the other methods then an alternative approach would be to have open() do a double check before returning.
> ie Just before open() completes it would need to synchonise and then check if close has already been called whilst open() was running.
> If so then open() should proceed to undo any resources it has just opened.
> One could perhaps argue that there's a problem with the state model if the framework might call close before open has completed; but I can imagine why this happens. 
> However, the must therefore deal with the consequential complexity of this deal with the threading issues effectively.



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