nwangtw commented on a change in pull request #3109: Add withStream() in
Streamlet to support stream selection
URL: https://github.com/apache/incubator-heron/pull/3109#discussion_r233965438
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File path: heron/api/src/java/org/apache/heron/streamlet/Streamlet.java
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@@ -71,6 +71,22 @@
*/
int getNumPartitions();
+ /**
+ * Set the id of the stream to be used by the children nodes.
+ * Usage (assuming source is a Streamlet object with two output streams:
stream1 and stream2):
+ * source.withStream("stream1").filter(...).log();
+ * source.withStream("stream2").filter(...).log();
+ * @param streamId The specified stream id
+ * @return Returns back the Streamlet with changed stream id
+ */
+ Streamlet<R> withStream(String streamId);
+
+ /**
+ * Gets the stream id of this Streamlet.
+ * @return the stream id of this Streamlet
+ */
+ String getStreamId();
Review comment:
Did a quick search, I think it is pretty close to the split operator in
Flink
(https://ci.apache.org/projects/flink/flink-docs-release-1.6/dev/stream/operators/).
In fact, select() seems to be a better name than "withStream". :D I will
think about it.
Neng gives a feedback about the withStream() function as a new user and he
made a good point that we need to handle both cases:
1.
stream.map();
stream.withStream("a").map();
stream.map(); // this should be the default stream
stream.withStream("a").map();
2.
steam2 = stream.withString("a");
stream2.map(); // this should be the new stream
stream.map(); // this should be the default stream
And this is not supported with the current implementation since the this
object is muted. I am going to see what is the best way and update this PR.
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