processing from the most recent successfully-completed checkpoint; Flink restores application state and rolls back to the correct position in the input stream from a checkpoint before processing starts again. This means that Flink computes results as though the failure never occurred.</p>
<p>Before Flink 1.4.0, exactly-once semantics were limited to the scope of <em>a Flink application only</em> and did not extend to most of the external systems to which Flink sends data after processing.</p>
<p>But Flink a