p>
</li>
<li>
<p><code>onTimer()</code> is called by Flink when a previously-registered timer
fires. Both event time and processing time timers are supported.</p>
</li>
<li>
<p><code>open()</code> is equivalent to a constructor. It is called inside of the
<a href="//nightlies.apache.org/flink/flink-docs-release-1.11/concepts/glossary.html#flink-taskmanager">TaskManager&rsquo;s</a>
JVM, and is used for initialization, such as registering
Flink-managed state. It is also the right place to initialize fields
th