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| <div class="sub-title"><span class="package-label-in-type">Package</span> <a href="package-summary.html">org.apache.kafka.streams.processor</a></div> |
| <h1 title="Interface StreamPartitioner" class="title">Interface StreamPartitioner<K,<wbr>V></h1> |
| </div> |
| <section class="class-description" id="class-description"> |
| <dl class="notes"> |
| <dt>Type Parameters:</dt> |
| <dd><code>K</code> - the type of keys</dd> |
| <dd><code>V</code> - the type of values</dd> |
| </dl> |
| <hr> |
| <div class="type-signature"><span class="modifiers">public interface </span><span class="element-name type-name-label">StreamPartitioner<K,<wbr>V></span></div> |
| <div class="block">Determine how records are distributed among the partitions in a Kafka topic. If not specified, the underlying producer's |
| default partitioning strategy will be used to determine the partition. |
| <p> |
| Kafka topics are divided into one or more <i>partitions</i>. Since each partition must fit on the servers that host it, so |
| using multiple partitions allows the topic to scale beyond a size that will fit on a single machine. Partitions also enable you |
| to use multiple instances of your topology to process in parallel all of the records on the topology's source topics. |
| <p> |
| When a topology is instantiated, each of its sources are assigned a subset of that topic's partitions. That means that only |
| those processors in that topology instance will consume the records from those partitions. In many cases, Kafka Streams will |
| automatically manage these instances, and adjust when new topology instances are added or removed. |
| <p> |
| Some topologies, though, need more control over which records appear in each partition. For example, some topologies that have |
| stateful processors may want all records within a range of keys to always be delivered to and handled by the same topology instance. |
| An upstream topology producing records to that topic can use a custom <i>stream partitioner</i> to precisely and consistently |
| determine to which partition each record should be written. |
| <p> |
| To do this, create a <code>StreamPartitioner</code> implementation, and when you build your topology specify that custom partitioner |
| when <a href="../Topology.html#addSink(java.lang.String,java.lang.String,org.apache.kafka.common.serialization.Serializer,org.apache.kafka.common.serialization.Serializer,org.apache.kafka.streams.processor.StreamPartitioner,java.lang.String...)"><code>adding a sink</code></a> |
| for that topic. |
| <p> |
| All StreamPartitioner implementations should be stateless and a pure function so they can be shared across topic and sink nodes.</div> |
| <dl class="notes"> |
| <dt>See Also:</dt> |
| <dd> |
| <ul class="see-list-long"> |
| <li><a href="../Topology.html#addSink(java.lang.String,java.lang.String,org.apache.kafka.common.serialization.Serializer,org.apache.kafka.common.serialization.Serializer,org.apache.kafka.streams.processor.StreamPartitioner,java.lang.String...)"><code>Topology.addSink(String, String, org.apache.kafka.common.serialization.Serializer, org.apache.kafka.common.serialization.Serializer, StreamPartitioner, String...)</code></a></li> |
| <li><a href="../Topology.html#addSink(java.lang.String,java.lang.String,org.apache.kafka.streams.processor.StreamPartitioner,java.lang.String...)"><code>Topology.addSink(String, String, StreamPartitioner, String...)</code></a></li> |
| </ul> |
| </dd> |
| </dl> |
| </section> |
| <section class="summary"> |
| <ul class="summary-list"> |
| <!-- ========== METHOD SUMMARY =========== --> |
| <li> |
| <section class="method-summary" id="method-summary"> |
| <h2>Method Summary</h2> |
| <div id="method-summary-table"> |
| <div class="table-tabs" role="tablist" aria-orientation="horizontal"><button id="method-summary-table-tab0" role="tab" aria-selected="true" aria-controls="method-summary-table.tabpanel" tabindex="0" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table', 3)" class="active-table-tab">All Methods</button><button id="method-summary-table-tab2" role="tab" aria-selected="false" aria-controls="method-summary-table.tabpanel" tabindex="-1" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table-tab2', 3)" class="table-tab">Instance Methods</button><button id="method-summary-table-tab3" role="tab" aria-selected="false" aria-controls="method-summary-table.tabpanel" tabindex="-1" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table-tab3', 3)" class="table-tab">Abstract Methods</button><button id="method-summary-table-tab5" role="tab" aria-selected="false" aria-controls="method-summary-table.tabpanel" tabindex="-1" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table-tab5', 3)" class="table-tab">Default Methods</button><button id="method-summary-table-tab6" role="tab" aria-selected="false" aria-controls="method-summary-table.tabpanel" tabindex="-1" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table-tab6', 3)" class="table-tab">Deprecated Methods</button></div> |
| <div id="method-summary-table.tabpanel" role="tabpanel"> |
| <div class="summary-table three-column-summary" aria-labelledby="method-summary-table-tab0"> |
| <div class="table-header col-first">Modifier and Type</div> |
| <div class="table-header col-second">Method</div> |
| <div class="table-header col-last">Description</div> |
| <div class="col-first even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3 method-summary-table-tab6"><code><a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Integer.html" title="class or interface in java.lang" class="external-link">Integer</a></code></div> |
| <div class="col-second even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3 method-summary-table-tab6"><code><a href="#partition(java.lang.String,K,V,int)" class="member-name-link">partition</a><wbr>(<a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/String.html" title="class or interface in java.lang" class="external-link">String</a> topic, |
| <a href="StreamPartitioner.html" title="type parameter in StreamPartitioner">K</a> key, |
| <a href="StreamPartitioner.html" title="type parameter in StreamPartitioner">V</a> value, |
| int numPartitions)</code></div> |
| <div class="col-last even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab3 method-summary-table-tab6"> |
| <div class="block"><span class="deprecated-label">Deprecated.</span></div> |
| </div> |
| <div class="col-first odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab5"><code>default <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/Optional.html" title="class or interface in java.util" class="external-link">Optional</a><<a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/Set.html" title="class or interface in java.util" class="external-link">Set</a><<a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Integer.html" title="class or interface in java.lang" class="external-link">Integer</a>>></code></div> |
| <div class="col-second odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab5"><code><a href="#partitions(java.lang.String,K,V,int)" class="member-name-link">partitions</a><wbr>(<a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/String.html" title="class or interface in java.lang" class="external-link">String</a> topic, |
| <a href="StreamPartitioner.html" title="type parameter in StreamPartitioner">K</a> key, |
| <a href="StreamPartitioner.html" title="type parameter in StreamPartitioner">V</a> value, |
| int numPartitions)</code></div> |
| <div class="col-last odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab5"> |
| <div class="block">Determine the number(s) of the partition(s) to which a record with the given key and value should be sent, |
| for the given topic and current partition count</div> |
| </div> |
| </div> |
| </div> |
| </div> |
| </section> |
| </li> |
| </ul> |
| </section> |
| <section class="details"> |
| <ul class="details-list"> |
| <!-- ============ METHOD DETAIL ========== --> |
| <li> |
| <section class="method-details" id="method-detail"> |
| <h2>Method Details</h2> |
| <ul class="member-list"> |
| <li> |
| <section class="detail" id="partition(java.lang.String,K,V,int)"> |
| <h3 id="partition(java.lang.String,java.lang.Object,java.lang.Object,int)">partition</h3> |
| <div class="member-signature"><span class="annotations"><a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Deprecated.html" title="class or interface in java.lang" class="external-link">@Deprecated</a> |
| </span><span class="return-type"><a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Integer.html" title="class or interface in java.lang" class="external-link">Integer</a></span> <span class="element-name">partition</span><wbr><span class="parameters">(<a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/String.html" title="class or interface in java.lang" class="external-link">String</a> topic, |
| <a href="StreamPartitioner.html" title="type parameter in StreamPartitioner">K</a> key, |
| <a href="StreamPartitioner.html" title="type parameter in StreamPartitioner">V</a> value, |
| int numPartitions)</span></div> |
| <div class="deprecation-block"><span class="deprecated-label">Deprecated.</span></div> |
| <div class="block">Determine the partition number for a record with the given key and value and the current number of partitions.</div> |
| <dl class="notes"> |
| <dt>Parameters:</dt> |
| <dd><code>topic</code> - the topic name this record is sent to</dd> |
| <dd><code>key</code> - the key of the record</dd> |
| <dd><code>value</code> - the value of the record</dd> |
| <dd><code>numPartitions</code> - the total number of partitions</dd> |
| <dt>Returns:</dt> |
| <dd>an integer between 0 and <code>numPartitions-1</code>, or <code>null</code> if the default partitioning logic should be used</dd> |
| </dl> |
| </section> |
| </li> |
| <li> |
| <section class="detail" id="partitions(java.lang.String,K,V,int)"> |
| <h3 id="partitions(java.lang.String,java.lang.Object,java.lang.Object,int)">partitions</h3> |
| <div class="member-signature"><span class="modifiers">default</span> <span class="return-type"><a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/Optional.html" title="class or interface in java.util" class="external-link">Optional</a><<a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/Set.html" title="class or interface in java.util" class="external-link">Set</a><<a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Integer.html" title="class or interface in java.lang" class="external-link">Integer</a>>></span> <span class="element-name">partitions</span><wbr><span class="parameters">(<a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/String.html" title="class or interface in java.lang" class="external-link">String</a> topic, |
| <a href="StreamPartitioner.html" title="type parameter in StreamPartitioner">K</a> key, |
| <a href="StreamPartitioner.html" title="type parameter in StreamPartitioner">V</a> value, |
| int numPartitions)</span></div> |
| <div class="block">Determine the number(s) of the partition(s) to which a record with the given key and value should be sent, |
| for the given topic and current partition count</div> |
| <dl class="notes"> |
| <dt>Parameters:</dt> |
| <dd><code>topic</code> - the topic name this record is sent to</dd> |
| <dd><code>key</code> - the key of the record</dd> |
| <dd><code>value</code> - the value of the record</dd> |
| <dd><code>numPartitions</code> - the total number of partitions</dd> |
| <dt>Returns:</dt> |
| <dd>an Optional of Set of integers between 0 and <code>numPartitions-1</code>, |
| Empty optional means using default partitioner |
| Optional of an empty set means the record won't be sent to any partitions i.e drop it. |
| Optional of Set of integers means the partitions to which the record should be sent to.</dd> |
| </dl> |
| </section> |
| </li> |
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| </section> |
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