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https://issues.apache.org/jira/browse/FLINK-7468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16296559#comment-16296559
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ASF GitHub Bot commented on FLINK-7468:
---------------------------------------
Github user NicoK commented on a diff in the pull request:
https://github.com/apache/flink/pull/4559#discussion_r157706995
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/PipelinedSubpartition.java
---
@@ -52,6 +54,10 @@
/** Flag indicating whether the subpartition has been released. */
private volatile boolean isReleased;
+ /** The number of non-event buffers currently in this subpartition */
+ @GuardedBy("buffers")
+ private volatile int buffersInBacklog;
--- End diff --
Your absolutely right about not counting events . Therefore, we cannot use
the queue's size as I suggested.
Yes, `BufferAndAvailability` would need to be extended as well.
This integration/split of the spillable/spilled subpartitions and
subpartition views and both of them working on the same structures requiring
the same synchronisation pattern is imho really not nice and highly fragile.
@pnowojski and me are currently re-designing the synchronisation in these parts
of the code and are a bit sensitive to it now so let's drag him into this
discussion as well: I would consider `PipelinedSubpartition` the hot path where
we need to optimise most - spillable subpartitions are used in batch mode and
have higher tolerances, especially when spilling to disk. if you returned the
new backlog counter in `SpillableSubpartition#decreaseBuffersInBacklog()`
however (retrieved under the `synchronized (buffers)` section), then you would
not need the `volatile` either since you are already under the lock.
> Implement sender backlog logic for credit-based
> -----------------------------------------------
>
> Key: FLINK-7468
> URL: https://issues.apache.org/jira/browse/FLINK-7468
> Project: Flink
> Issue Type: Sub-task
> Components: Network
> Reporter: zhijiang
> Assignee: zhijiang
> Fix For: 1.5.0
>
>
> This is a part of work for credit-based network flow control.
> Receivers should know how many buffers are available on the sender side (the
> backlog). The receivers use this information to decide how to distribute
> floating buffers.
> The {{ResultSubpartition}} maintains the backlog which only indicates the
> number of buffers in this subpartition, not including the number of events.
> The backlog is increased for adding buffer to this subpartition, and
> decreased for polling buffer from it.
> The backlog is attached in {{BufferResponse}} by sender as an absolute value
> after the buffer being transferred.
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