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https://issues.apache.org/jira/browse/RATIS-1923?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17783689#comment-17783689
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Tsz-wo Sze commented on RATIS-1923:
-----------------------------------
[~tanxinyu], you are right! The javadoc said that "the function is applied at
most once per key." Thanks the for info.
https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentHashMap.html#computeIfAbsent-K-java.util.function.Function-
> Netty: atomic operations require side-effect-free functions
> -----------------------------------------------------------
>
> Key: RATIS-1923
> URL: https://issues.apache.org/jira/browse/RATIS-1923
> Project: Ratis
> Issue Type: Bug
> Components: Netty
> Reporter: Tsz-wo Sze
> Assignee: Tsz-wo Sze
> Priority: Major
> Fix For: 3.0.0
>
> Attachments: for-loop.jpg, screenshot-1.png
>
> Time Spent: 40m
> Remaining Estimate: 0h
>
> - The update methods in AtomicReference run in a loop and may call the update
> function multiple time. The old values created by the update function may be
> discarded without cleaning up. In NettyClientStreamRpc.Connection the connect
> method is not side-effect-free. Although it passes a [MemoizedSupplier to
> getAndUpdate|https://github.com/apache/ratis/blob/47e5b6aa148cfe777fb3b7742154fe6b417ea42a/ratis-netty/src/main/java/org/apache/ratis/netty/client/NettyClientStreamRpc.java#L187-L188],
> it still is possible that a value is supplied but then discarded in the
> AtomicReference loop.
> - Similarly, the computeIfAbsent in ConcurrentHashMap also runs in a loop
> and may call the mapping function multiple times. DataStreamMap is
> implemented using a ConcurrentHashMap. However, [the mapping function is not
> side-effect-free|https://github.com/apache/ratis/blob/47e5b6aa148cfe777fb3b7742154fe6b417ea42a/ratis-netty/src/main/java/org/apache/ratis/netty/server/DataStreamManagement.java#L281-L289]
> although it uses a MemoizedSupplier.
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