[GitHub] flink pull request #4368: [FLINK-7210] Introduce TwoPhaseCommitSinkFunction

[tzulitai <gi...@git.apache.org>]

Github user tzulitai commented on a diff in the pull request:

    https://github.com/apache/flink/pull/4368#discussion_r131070533
  
    --- Diff: flink-streaming-java/src/main/java/org/apache/flink/streaming/api/functions/sink/TwoPhaseCommitSinkFunction.java ---
    @@ -51,39 +48,52 @@
      * @param <TXN> Transaction to store all of the information required to handle a transaction (must be Serializable)
      */
     @PublicEvolving
    -public abstract class TwoPhaseCommitSinkFunction<IN, TXN extends Serializable>
    +public abstract class TwoPhaseCommitSinkFunction<IN, TXN>
     		extends RichSinkFunction<IN>
     		implements CheckpointedFunction, CheckpointListener {
     
     	private static final Logger LOG = LoggerFactory.getLogger(TwoPhaseCommitSinkFunction.class);
     
    -	protected final ListStateDescriptor<TransactionAndCheckpoint<TXN>> pendingCommitTransactionsDescriptor;
    +	protected final ListStateDescriptor<Map<Long, TXN>> pendingCommitTransactionsDescriptor;
     	protected final ListStateDescriptor<TXN> pendingTransactionsDescriptor;
     
    -	protected final List<TransactionAndCheckpoint<TXN>> pendingCommitTransactions = new ArrayList<>();
    +	protected final LinkedHashMap<Long, TXN> pendingCommitTransactions = new LinkedHashMap<>();
     
     	@Nullable
     	protected TXN currentTransaction;
     	protected ListState<TXN> pendingTransactionsState;
    -	protected ListState<TransactionAndCheckpoint<TXN>> pendingCommitTransactionsState;
    -
    -	public TwoPhaseCommitSinkFunction(Class<TXN> txnClass) {
    -		this(
    -			TypeInformation.of(txnClass),
    -			TypeInformation.of(new TypeHint<TransactionAndCheckpoint<TXN>>() {}));
    -	}
    +	protected ListState<Map<Long, TXN>> pendingCommitTransactionsState;
    --- End diff --
    
    I think this has to be `ListState<Tuple2<Long, TXN>>` or the original `ListState<TransactionAndCheckpoint<TXN>>`.
    
    Using a map instead of a list for `pendingCommitTransactions ` is ok for bookkeeping, but when snapshotting this map we need to make sure the snapshotted transactions are state elements that can be redistributable independent of each other. 


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