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https://issues.apache.org/jira/browse/FLINK-3428?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15261999#comment-15261999
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ASF GitHub Bot commented on FLINK-3428:
---------------------------------------
Github user rmetzger commented on a diff in the pull request:
https://github.com/apache/flink/pull/1764#discussion_r61411342
--- Diff:
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/functions/AscendingTimestampExtractor.java
---
@@ -20,123 +20,18 @@
import org.apache.flink.annotation.PublicEvolving;
-import org.apache.flink.streaming.api.watermark.Watermark;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import static java.util.Objects.requireNonNull;
-
/**
* A timestamp assigner and watermark generator for streams where
timestamps are monotonously
* ascending. In this case, the local watermarks for the streams are easy
to generate, because
* they strictly follow the timestamps.
*
+ * <b>Note:</b> This is just a stub class. The actual code for this has
moved to
+ * {@link
org.apache.flink.streaming.api.functions.timestamps.AscendingTimestampExtractor}.
+ *
--- End diff --
What's the reasoning behind this stub class?
> Add fixed time trailing timestamp/watermark extractor
> -----------------------------------------------------
>
> Key: FLINK-3428
> URL: https://issues.apache.org/jira/browse/FLINK-3428
> Project: Flink
> Issue Type: Improvement
> Reporter: Robert Metzger
> Assignee: Kostas Kloudas
>
> Flink currently provides only one build-in timestamp extractor, which assumes
> strictly ascending timestamps. In real world use cases, timestamps are almost
> never strictly ascending.
> Therefore, I propose to provide an utility watermark extractor which is
> generating watermarks with a fixed-time trailing.
> The implementation should keep track of the highest event-time seen so far
> and subtract a fixed amount of time from that event time.
> This way, users can for example specify that the watermarks should always
> "lag behind" 10 minutes.
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