Stephan Ewen created FLINK-3435:
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Summary: Change interplay of Ingestion Time and Event Time
Key: FLINK-3435
URL: https://issues.apache.org/jira/browse/FLINK-3435
Project: Flink
Issue Type: Improvement
Components: Streaming
Affects Versions: 0.10.2
Reporter: Stephan Ewen
Fix For: 1.0.0
Currently, "EventTime" and "IngestionTime" are completely the same.
For both happens the following:
- Sources generate ingestion time timestamps and watermarks
- If a user adds a manual timestamp extractor / watermark generator, then
those override the ingestion time timestamps and watermarks
- That implies that event time on a certain input falls back to ingestion
time, if one forgets (or incorrectly uses) the timestamp extractors
- Also, Ingestion Time and Event Time simply mix if some inputs have
timestamp assigners, and others have not.
This behavior is quite tricky to understand. After some discussions with
[~aljoscha] and [~rmetzger], we suggest to change it the following way.
1. On Ingestion Time, the timestamps and watermarks are generated as they are
now.
2. On event time, no default timestamps and watermarks are generated. If a
user does not implement a timestamp extractor / watermark generator, then the
event time operations will fail fast.
3. If one wants to use ingestion time on event time settings (mix), one can
use an explicit "WallClockTimetampsAndWatermark" generator.
4. Later, the "Ingestion Time" settings should automatically disable and
user-defined timestamp extractors / assigners.
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