th data sources and data sinks via the two-phase commit protocol to deliver <em>end-to-end</em> exactly-once guarantees.</li>
<li>Walk through a simple example on how to use <code>TwoPhaseCommitSinkFunction</code> to implement an exactly-once file sink.</li>
</ul>
<h2 id="exactly-once-semantics-within-an-apache-flink-application">
  Exactly-once Semantics Within an Apache Flink Application
  <a class="anchor" href="#exactly-once-semantics-within-an-apache-flink-application">#</a>
</h2>
<p>When we say &ldquo