[jira] [Commented] (KAFKA-20880) Consider to address inconsistency in `StandbyUpdateListener` API

["Eduwer Camacaro (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-20880?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18101721#comment-18101721 ] 

Eduwer Camacaro commented on KAFKA-20880:
-----------------------------------------

I also consider this to be an inconsistency in these two callbacks that track the restoration of state stores for both active and standby tasks. Additionally, it is weird to me that we didn't notice that the Javadoc for the tasksId argument on the StandbyUpdateListener#batchUpdated method when implementing the KIP. 

However, I don't think the TaskId is irrelevant information on these callbacks because it allows the users to add trace, debug, or info log entries that print the restoration lag of the stores that are inside of a single task. Additionally, users might want to add a metric that groups the total restoration lag for all the stores in the task.

I understand that the TaskId is not a concept that users should usually need to worry about, but sometimes it is useful for users to understand some information about the assigned tasks on a single instance, so I propose to solve this by adding the TaskId argument for both `StateRestoreListener` and `StandbyUpdateListener`.

 

> Consider to address inconsistency in `StandbyUpdateListener` API
> ----------------------------------------------------------------
>
>                 Key: KAFKA-20880
>                 URL: https://issues.apache.org/jira/browse/KAFKA-20880
>             Project: Kafka
>          Issue Type: Improvement
>          Components: streams
>            Reporter: Matthias J. Sax
>            Priority: Minor
>              Labels: needs-kip
>
> Kafka Streams has two state-restore-listeners: `StateRestoreListener` and `StandbyUpdateListener`.
> `StandbyUpdateListener#onBatchLoaded()` is the only method that has a `TaskId` parameter. It's unclear why we have this inconsitency.
> Technically, `TaskId` should not be relevant, because the listener is for a store, not a task, it would fire for all stores for a task. And `TopicPartition` and `storeName` are already passed in which is the more relevant information.



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