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https://issues.apache.org/jira/browse/FLINK-6988?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16092701#comment-16092701
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ASF GitHub Bot commented on FLINK-6988:
---------------------------------------

Github user tzulitai commented on the issue:

    https://github.com/apache/flink/pull/4239
  
    Thanks a lot for opening a pull request for this very important feature 
@pnowojski.
    I did a rough first pass and had some comments I would like to clear out 
first (this is a big chunk of code, we would probably need to go through this 
quite a few times before it can be mergeable.)
    
    Most notably, some comments so far:
    1. I think we need UTs for the `TwoPhaseCommitSinkFunction`. It alone is a 
very important addition (I would even prefer a separate PR for it and try to 
merge that first.)
    2. Serialization of the transaction state in `TwoPhaseCommitSinkFunction` 
needs to be changed
    2. Is the `FlinkKafkaProducer011` actually supporting hybrid (normal sink 
function and `writeToKafkaWithTimestamps` as a custom sink operator)? From the 
looks of it, it doesn't seem like it.


> Add Apache Kafka 0.11 connector
> -------------------------------
>
>                 Key: FLINK-6988
>                 URL: https://issues.apache.org/jira/browse/FLINK-6988
>             Project: Flink
>          Issue Type: Improvement
>          Components: Kafka Connector
>    Affects Versions: 1.3.1
>            Reporter: Piotr Nowojski
>            Assignee: Piotr Nowojski
>
> Kafka 0.11 (it will be released very soon) add supports for transactions. 
> Thanks to that, Flink might be able to implement Kafka sink supporting 
> "exactly-once" semantic. API changes and whole transactions support is 
> described in 
> [KIP-98|https://cwiki.apache.org/confluence/display/KAFKA/KIP-98+-+Exactly+Once+Delivery+and+Transactional+Messaging].
> The goal is to mimic implementation of existing BucketingSink. New 
> FlinkKafkaProducer011 would 
> * upon creation begin transaction, store transaction identifiers into the 
> state and would write all incoming data to an output Kafka topic using that 
> transaction
> * on `snapshotState` call, it would flush the data and write in state 
> information that current transaction is pending to be committed
> * on `notifyCheckpointComplete` we would commit this pending transaction
> * in case of crash between `snapshotState` and `notifyCheckpointComplete` we 
> either abort this pending transaction (if not every participant successfully 
> saved the snapshot) or restore and commit it. 



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