[jira] [Commented] (FLINK-5416) Function wrappers should support CheckpointedFunction

["Eron Wright (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-5416?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15801847#comment-15801847 ] 

Eron Wright  commented on FLINK-5416:
-------------------------------------


To fix it, the wrapper would assumedly implement `CheckpointedFunction` and contain logic similar to that found in `AbstractUdfStreamOperator` (notably the handling of `ListCheckpointed`).   Maybe the logic could be encapsulated in `FunctionUtils` since numerous wrappers exist.

> Function wrappers should support CheckpointedFunction 
> ------------------------------------------------------
>
>                 Key: FLINK-5416
>                 URL: https://issues.apache.org/jira/browse/FLINK-5416
>             Project: Flink
>          Issue Type: Bug
>          Components: State Backends, Checkpointing
>            Reporter: Eron Wright 
>
> The `CheckpointedFunction` interface was introduced to provide user functions with a context for partitioned state storage.   This works for user functions that are provided directly to the operator (assuming it extends from `AbstractUdfStreamOperator`).   However, I see that some operators wrap the user function in an internal function (e.g. `WrappingFunction`,  `InternalWindowFunction`).   This defeats the callbacks on `CheckpointedFunction` because those wrappers don’t implement `CheckpointedFunction`. 
> For example, the user function passed to `WindowedStream::apply` will get callbacks for `RichFunction` but not for `CheckpointedFunction`.



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