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https://issues.apache.org/jira/browse/FLINK-11082?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16739385#comment-16739385
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Piotr Nowojski commented on FLINK-11082:
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Another issue.
Could this bug might explain why one user was recently reporting higher CPU
usage and 300% increase in number of packets being sent between the nodes after
upgrading from Flink 1.4? Previously we were aware that credit base flow
control increases the network traffic/number of messages sent between nodes by
100%. But if we announce the fresh partial buffers immediately to the receiver,
could it be that the small chunk of that data is being sent prematurely, before
{{flushRequested}} or next {{BufferConsumer}} is enqueued? Sending chunk of
data prematurely and assigning new credit would explain the remaining
unaccounted "200%" number of messages being sent.
Btw, [~zjwang] if channel is idle, two exclusive buffers will be assigned to
the sender and he will have some buffers for immediate use whenever the channel
becomes active?
> Increase backlog only if it is available for consumption
> --------------------------------------------------------
>
> Key: FLINK-11082
> URL: https://issues.apache.org/jira/browse/FLINK-11082
> Project: Flink
> Issue Type: Sub-task
> Components: Network
> Affects Versions: 1.5.6, 1.6.3, 1.7.1, 1.8.0
> Reporter: zhijiang
> Assignee: zhijiang
> Priority: Major
>
> The backlog should indicate how many buffers are available in subpartition
> for downstream's consumption. The availability is considered from two
> factors. One is {{BufferConsumer}} finished, and the other is flush triggered.
> In current implementation, when the {{BufferConsumer}} is added into the
> subpartition, then the backlog is increased as a result, but this
> {{BufferConsumer}} is not yet available for network transport.
> Furthermore, the backlog would affect requesting floating buffers on
> downstream side. That means some floating buffers are fetched in advance but
> not be used for long time, so the floating buffers are not made use of
> efficiently.
> We found this scenario extremely for rebalance selector on upstream side, so
> we want to change when to increase backlog by finishing {{BufferConsumer}} or
> flush triggered.
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