Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/flink/pull/1563#discussion_r51428065
--- Diff: docs/apis/streaming/index.md ---
@@ -1768,6 +1768,11 @@ greater than 1, the output will also be prepended
with the identifier of the tas
</div>
</div>
+Note that the `write*()` methods on `DataStream` are mainly intended for
debugging purposes.
+They are not participating in Flink's checkpointing (no fault tolerance
guarantees). The
--- End diff --
May be worth adding that this means usually "at-least-once" , but may also
mean data loss in cases where the output formats buffer data and do not
immediately persist it.
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