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https://issues.apache.org/jira/browse/FLINK-7428?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16123525#comment-16123525
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ASF GitHub Bot commented on FLINK-7428:
---------------------------------------
Github user NicoK commented on the issue:
https://github.com/apache/flink/pull/4529
FYI:
- newer netty 4.0.xx versions also use `buffer.slice(index, length)` inside
their `extractFrame()` method (see
https://github.com/netty/netty/commit/891be30a28c6dc5a1edf1cb5a3690644cf4ff66e)
and despite the comment on `extractFrame()`, this is also safe when used
outside the `decode()` method as long as the buffer is retained (and then
released later). By letting `NettyMessageDecoder` inherit from
`LengthFieldBasedFrameDecoder` though, we also gain a smaller channel handler
pipeline.
- netty 4.1 offers an even improved `buffer.retainedSlice(index, length)`
implementation (see
https://github.com/netty/netty/commit/3a9f47216143082bdfba62e8940160856767d672)
but we can't go that way yet due to our netty-router dependency
> avoid one additional buffer copy when receiving messages
> --------------------------------------------------------
>
> Key: FLINK-7428
> URL: https://issues.apache.org/jira/browse/FLINK-7428
> Project: Flink
> Issue Type: Improvement
> Components: Network
> Affects Versions: 1.4.0
> Reporter: Nico Kruber
> Assignee: Nico Kruber
>
> By using {{LengthFieldBasedFrameDecoder}}, we create one unnecessary (netty)
> buffer copy in this class which could be easily avoided since we can ensure
> that the buffer is free to be released after decoding it in the
> {{NettyMessageDecoder}} and into our own buffer and/or events.
> The solution would be to make {{NettyMessageDecoder}} extend from
> {{LengthFieldBasedFrameDecoder}} and handle the decoding of the frames and
> the objects in there. In the frame creation otherwise done by
> {{LengthFieldBasedFrameDecoder}}, we could use a sliced buffer instead. This
> solution also makes the channel pipelines a bit simpler.
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