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https://issues.apache.org/jira/browse/FLINK-7468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16295304#comment-16295304
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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_r157544794
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/ResultSubpartition.java
---
@@ -99,6 +82,23 @@ protected Throwable getFailureCause() {
abstract public boolean isReleased();
+ /**
+ * Gets the number of non-event buffers in this subpartition.
+ */
+ abstract public int getBuffersInBacklog();
+
+ /**
+ * Decreases the number of non-event buffers by one after fetching a
non-event
+ * buffer from this subpartition.
+ */
+ abstract public void decreaseBuffersInBacklog(Buffer buffer);
+
+ /**
+ * Increases the number of non-event buffers by one after adding a
non-event
+ * buffer into this subpartition.
+ */
+ abstract public void increaseBuffersInBacklog(Buffer buffer);
--- End diff --
I'm not quite sure the latter two methods should be in `ResultSubpartition`
now since they are quite internal. `increaseBuffersInBacklog()` is only called
by `PipelinedSubpartition` and `SpillableSubpartition`.
`decreaseBuffersInBacklog()` is (additionally) only by spilled/spillable
subpartition views and therefore could be package-private in
`SpillableSubpartition` only.
> 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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