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https://issues.apache.org/jira/browse/FLINK-3336?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15132894#comment-15132894
]
ASF GitHub Bot commented on FLINK-3336:
---------------------------------------
Github user uce commented on a diff in the pull request:
https://github.com/apache/flink/pull/1589#discussion_r51928771
--- Diff:
flink-streaming-scala/src/main/scala/org/apache/flink/streaming/api/scala/DataStream.scala
---
@@ -371,6 +371,30 @@ class DataStream[T](stream: JavaStream[T]) {
def rebalance: DataStream[T] = stream.rebalance()
/**
+ * Sets the partitioning of the [[DataStream]] so that the output tuples
+ * are distributed evenly to a subset of instances the downstream
operation.
+ *
+ * The subset of downstream operations to which the upstream operation
sends
+ * elements depends on the degree of parallelism of both the upstream
and downstream operation.
+ * For example, if the upstream operation has parallelism 2 and the
downstream operation
+ * has parallelism 4, then one upstream operation would distribute
elements to two
+ * downstream operations while the other upstream operation would
distribute to the other
+ * two downstream operations. If, on the other hand, the downstream
operation has parallelism
+ * 2 while the upstream operation has parallelism 4 then two upstream
operations will
+ * distribute to one downstream operation while the other two upstream
operations will
+ * distribute to the other downstream operations.
+ *
+ * In cases where the different parallelisms are not multiples of each
other one or several
+ * downstream operations will have a differing number of inputs from
upstream operations.
+ *
+ * This setting only effects
+ * the how the outputs will be distributed between the parallel
instances of
+ * the next processing operator.
+ */
+ def semiRebalance: DataStream[T] = stream.semiRebalance()
+
+
--- End diff --
Empty line and comment from Java DataStream
> Add Semi-Rebalance Data Shipping for DataStream
> -----------------------------------------------
>
> Key: FLINK-3336
> URL: https://issues.apache.org/jira/browse/FLINK-3336
> Project: Flink
> Issue Type: Improvement
> Components: Streaming
> Reporter: Aljoscha Krettek
> Assignee: Aljoscha Krettek
> Fix For: 1.0.0
>
>
> This feature has recently been requested on the ML:
> http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Distribution-of-sinks-among-the-nodes-td4640.html
> The new data shipping pattern would allow to rebalance data only to a subset
> of downstream operations.
> The subset of downstream operations to which the upstream operation would send
> elements depends on the degree of parallelism of both the upstream and
> downstream operation.
> For example, if the upstream operation has parallelism 2 and the downstream
> operation
> has parallelism 4, then one upstream operation would distribute elements to
> two
> downstream operations while the other upstream operation would distribute to
> the other
> two downstream operations. If, on the other hand, the downstream operation
> had parallelism
> 2 while the upstream operation has parallelism 4 then two upstream operations
> would
> distribute to one downstream operation while the other two upstream
> operations would
> distribute to the other downstream operations.
> In cases where the different parallelisms are not multiples of each other one
> or several
> downstream operations would have a differing number of inputs from upstream
> operations.
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