mjsax commented on code in PR #16316:
URL: https://github.com/apache/kafka/pull/16316#discussion_r1637372406
##########
docs/streams/upgrade-guide.html:
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@@ -303,6 +303,62 @@ <h3><a id="streams_api_changes_350"
href="#streams_api_changes_350">Streams API
adds a new config <code>default.client.supplier</code> that allows to
use a custom <code>KafkaClientSupplier</code> without any code changes.
</p>
+ <h3><a id="streams_api_changes_330"
href="#streams_api_changes_330">Streams API changes in 3.3.0</a></h3>
+ <p>
+ Kafka Streams does not send a "leave group" request when an instance is
closed. This behavior implies
+ that a rebalance is delayed until max.poll.interval.ms passed.
+ <a
href="https://cwiki.apache.org/confluence/display/KAFKA/KIP-812%3A+Introduce+another+form+of+the+%60KafkaStreams.close%28%29%60+API+that+forces+the+member+to+leave+the+consumer+group";>KIP-812</a>
+ introduces <code>KafkaStreams.close(CloseOptions)</code> overload which
allows to force an instance to leave the
+ group immediately.
+
+ Note: due to internal limitations, <code>CloseOptions</code> only works
for static consumer groups at this point
+ (cf. <a
href="https://issues.apache.org/jira/browse/KAFKA-16514";>KAFKA-16514</a> for
more details and a fix in
+ some future release).
+ </p>
+
+ <p>
+ <a
href="https://cwiki.apache.org/confluence/display/KAFKA/KIP-820%3A+Extend+KStream+process+with+new+Processor+API";>KIP-820</a>
+ adapts the PAPI type-safety improvement of KIP-478 into the DSL. The
existing methods <code>KStream.transform</code>,
+ <code>KStream.flatTransform</code>,
<code>KStream.transformValues</code>, and
<code>KStream.flatTransformValues</code>
+ as well as all overloads of <code>void KStream.process</code> are
deprecated in favor of the newly added methods
+ <ul>
+ <li><code>KStream<KOut,VOut> KStream.process(ProcessorSupplier,
...)</code></li>
+ <li><code>KStream<K,VOut>
KStream.processValues(FixedKeyProcessorSupplier, ...)</code></li>
+ </ul>
+ Both new methods have multiple overlaods and return a
<code>KStream</code> instead of <code>void</code> as the
+ deprecated <code>process()</code> methods did. In addition,
<code>FixedKeyProcessor</code>, <code>FixedKeyRecord</code>,
+ <code>FixedKeyProcessorContext</code>, and
<code>ContextualFixedKeyProcessor</code> are introduced to guard against
+ disallowed key modification inside <code>processValues()</code>.
Furthermore <code>ProcessingContext</code> is
+ added for a better interface hierarchy.
+ </p>
+
+ <p>
+ Emitting a windowed aggregation result only after a window is closed is
currently supported via the
+ <code>suppress()</code> operator. However, <code>suppress()</code> uses
an in-memory implementation and does not
+ support RocksDB. To close this gap,
+ <a
href="https://cwiki.apache.org/confluence/display/KAFKA/KIP-825%3A+introduce+a+new+API+to+control+when+aggregated+results+are+produced";>KIP-825</a>
+ introduces "emit strategies" which are built into the aggregation
operator directly to use the already existing
+ RocksDB store.
<code>TimeWindowedKStream.emitStrategy(EmitStrategy)</code> and
+ <code>SessionWindowedKStream.emitStrategy(EmitStrategy)</code> allow to
pick between "emit on window update" (default)
+ and "emit on window close" strategies. Additionally, a few new emit
metrics are added, as well as a necessary
+ new method <code>SessionStore.findSessions(long, long)</code>.
+ </p>
+
+ <p>
+ <a
href="https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=211882832";>KIP-834</a>
allows to pause
+ and resume a Kafka Streams instance. Pausing implies that processing
input records and executing punctuations will
+ be skipped; Kafka Streams will continue to poll to maintain its group
membership and may commit offsets.
+ In addition to the new method <code>KafkaStreams.pause()</code> and
<code>KafkaStreams.resume()</code>, it is also
+ supported to check if an instance is paused via
<code>KafkaStreams.isPaused()</code> method.
+ </p>
+
+ <p>
+ To improve monitoring of Kafka Streams applications, <a
href="https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=211886093";>KIP-846</a>
+ adds four new metrics <code>bytes-consumed-total</code>,
<code>records-consumed-total</code>,
+ <code>bytes-produced-total</code>, and
<code>records-produced-total</code> within a new <b>topic level</b> scope.
Review Comment:
These metrics are already added to the `ops.html` KS metrics section.
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