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Table of Contents

Status

Current state: Under Discussion Adopted (1.0)

Discussion thread: [DISCUS] KIP-182: Reduce Streams DSL overloads and allow easier use of custom storage engineshere [Change the link from the KIP proposal email archive to your own email thread]

JIRA: KAFKA-5651 

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

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Code Block
languagejava
titleKTable
<KR, VR> KGroupedTable<KR, VR> groupBy(final KeyValueMapper<? super K, ? super V, KeyValue<KR, VR>> selector, Serialized<KR, VR> serialized);

KTable<K, V> filter(final Predicate<? super K, ? super V> predicate, final Materialized<K, V, KeyValueStore<Bytes, byte[]>> materialized);

KTable<K, V> filterNot(final Predicate<? super K, ? super V> predicate, final Materialized<K, V, KeyValueStore<Bytes[], byte[]>> materialized);

<VR> KTable<K, VR> mapValues(final ValueMapper<? super V, ? extends VR> mapper, final Materialized<K, V, KeyValueStore<Bytes[], byte[]>> materialized);

void to(final String topic, final Produced<K, V> options);
 
KTable<K, V> through(final Serde<K> keySerde, final Produced<K, V> produced)

KTable<K, V> through(final String topic, final Produced<K, V> produced, final Materialized<K, V, KeyValueStore<Bytes, byte[]> options);

<VO, VR> KTable<K, VR> join(final KTable<K, VO> other,
<VO, VR> KTable<K, VR> join(final KTable<K, VO> other,
                                        final ValueJoiner<? super V, ? super VO, ? extends VR> joiner,
                            final Materialized<K, VR, KeyValueStore<Bytes, byte[]>> materialized);

<VO, VR> KTable<K, VR> leftJoin(final KTable<K, VO> other,
                                final ValueJoiner<? super V, ? super VO, ? extends VR> joiner,
                                final Materialized<K, VR, KeyValueStore<Bytes, byte[]>> materialized);

<VO, VR> KTable<K, VR> outerJoin(final KTable<K, VO> other,
                                 final ValueJoiner<? super V, ? super VO, ? extends VR> joiner,
                                 final Materialized<K, VR, KeyValueStore<Bytes, byte[]>> materialized);
 

 

We add some new helper methods to Stores so people can conveniently and quickly create basic StateStoreSuppliers for use in the DSL or PAPI. We will also deprecate the existing Stores.create(...)

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Code Block
languagejava
titleKGroupedStream
<W extends Window> WindowedKStream<KTimeWindowedKStream<K, V> windowedBy(Windows<W> timeWindows);

SessionWindowedKStream<K, V> windowedBy(SessionWindows sessionWindows);

KTable<K, Long> count(final Materialized<K, Long> materialized);

KTable<K, V> reduce(final Reducer<V> reducer, final Materialized<K, V, KeyValueStore<Bytes, byte[]>> materialized);

<VR> KTable<K, VR> aggregate(final Initializer<VR> initializer,
                             final Aggregator<? super K, ? super V, VR> aggregator,
                             final Serde<VR>Materialized<K, aggValueSerdeVR,
                             final Materialized<K, VR, KeyValueStore<Bytes, byteKeyValueStore<Bytes, byte[]>> materialized);


Code Block
languagejava
titleKGroupedTable
KTable<K, Long> count(final Materialized<K, V, KeyValueStore<Bytes, byte[]>> materialized);

KTable<K, V> reduce(final Reducer<V> adder, final Reducer<V> subtractor, final Materialized<K, V, KeyValueStore<Bytes, byte[]>> materialized);

<VR> KTable<K, VR> aggregate(final Initializer<VR> initializer,
                             final Aggregator<? super K, ? super V, VR> aggregator,
                             final Aggregator<? super K, ? super V, VR> subtractor,
                             final Materialized<K, VR, KeyValueStore<Bytes, byte[]>> materialized);

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Code Block
languagejava
titleStreamsBuilder
public synchronized <K, V> KStream<K, V> stream(final String topic)
 
public synchronized <K, V> KStream<K, V> stream(final String topic, final Consumed<K, V> options)
 
public synchronized <K, V> KStream<K, V> stream(final Collection<String> topic, final Consumed<K, V> options)
 
public synchronized <K, V> KStream<K, V> stream(final Collection<String> topic)

public synchronized <K, V> KStream<K, V> stream(final Pattern pattern, final Consumed<K, V> options)

public synchronized <K, V> KTable<K, V> table(final String topic, final Consumed<K, V> consumed)

public synchronized <K, V> KTable<K, V> table(final String topic, final Consumed<K, V> consumed, final Materialized<K, V, KeyValueStore<Bytes, byte[]>> materialized)
 
public synchronized <K, V> KTable<K, V> table(final String topic, final Materialized<K, V, KeyValueStore<Bytes, byte[]>> materialized)

public synchronized <K, V> GlobalKTable<K, V> globalTable(final String topic, final Consumed<K, V> consumed)
, V> consumed)

public synchronized <K, V> GlobalKTable<K, V> globalTable(final String topic, final Consumed<K, V> consumed, final Materialized<K, V, KeyValueStore<Bytes, byte[]>> materialized)
 
public synchronized <K, V> GlobalKTable<K, V> globalTable(final String topic, final Consumed<K, V> consumed, final Materialized<K, V, KeyValueStore<Bytes, byte[]>> materialized)

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Code Block
languagejava
titleWindowedKStream
public interface WindowedKStream<KTimeWindowedKStream<K, V> {

    KTable<Windowed<K>, Long> count();

    KTable<Windowed<K>, Long> count(final Materialized<K, Long, WindowStore<Bytes, byte[]>> materializedAs);

    <VR> KTable<Windowed<K>, VR> aggregate(final Initializer<VR> initializer,
                                           final Aggregator<? super K, ? super V, VR> aggregator);

    <VR> KTable<Windowed<K>, VR> aggregate(final Initializer<VR> initializer,
                                           final Aggregator<? super K, ? super V, VR> aggregator,
                                           final Materialized<K, VR, WindowStore<Bytes, byte[]>> materializedAs);


    KTable<Windowed<K>, V> reduce(final Reducer<V> reducer);

    KTable<Windowed<K>, V> reduce(final Reducer<V> reducer,
                                  final Materialized<K, V, WindowStore<Bytes, byte[]>> materializedAs);


} 

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Code Block
languagejava
titleConsumed
/**
 * Options for consuming a topic as a KStream or KTable
 */
public class Consumed<K, V> {
    public static <K, V>  Consumed<K, V> with(final Serde<K> keySerde, final Serde<V> valueSerde, final TimestampExtractor extractor, final Topology.AutoOffsetReset resetPolicy)
    public static <K, V>  Consumed<K, V> with(final Serde<K> keySerde, final Serde<V> valueSerde)
    public static <K, V>  Consumed<K, V> with(final TimestampExtractor extractor)
    public static <K, V>  Consumed<K, V> with(final Topology.AutoOffsetReset resetPolicy)
    
    public Consumed<K, V> withKeySerde(final Serde<K> keySerde)

    public Consumed<K, V> withValueSerde(final(final Serde<V> valueSerde)

    public Consumed<K, V> withTimestampExtractor(final TimestampExtractor timestampExtractor)

    public Consumed<K, V> withOffsetResetPolicy(final Topology.AutoOffsetReset resetPolicy)
 
	public Serde<K> keySerde()
 
	public Serde<V> valueSerde()
 
    public Consumed<K, V> withTimestampExtractor(final 	public TimestampExtractor timestampExtractor()
 
    	public Consumed<K, V> withOffsetResetPolicy(final TopologyToploogy.AutoOffsetReset resetPolicyoffsetResetPolicy()
}


Code Block
languagejava
titleStateStoreBuilder
/**
 * Implementations of this will provide the ability to wrap a given StateStore
 * with or without caching/loggging etc.
 */
public interface StateStoreBuilder<TStoreBuilder<T extends StateStore> {

    StateStoreBuilder<T>StoreBuilder<T> withCachingEnabled();
    StateStoreBuilder<T>StoreBuilder<T> withLoggingEnabled(Map<String, String> config);
    StoreBuilder<T> withLoggingDisabled()
    T build();
    Map<String, String> logConfig();
    boolean loggingEnabled();
}

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Code Block
/**
 * A store supplier that can be used to create one or more {@link SessionStore} instances of type &lt;Byte, byte[]&gt;
 */
public interface SessionBytesStoreSupplier extends StoreSupplier<SessionStore<Bytes, byte[]>> {

    /**
     * The size of a segment, in milliseconds. Used when caching is enabled to segment the cache
     * and reduce the amount of data that needs to be scanned when performing range queries
     *
     * @return segmentInterval in milliseconds
     */
    long segmentIntervalsegmentIntervalMs();
}

 

Proposed Changes

Add the above methods, interfaces, classes to the DSL. Deprecate existing overloads on KStream, KTable, and KGroupedStream that take more than the required parameters, for example, KTable#filter(Predicate, String) and KTable#filter(Predicate, StateStoreSupplier) will be deprecated. StateStoreSupplier will also be deprecated deprecated. All versions of KTable#through and KTable#to will be deprecated in favour of using KTable#toStream()#through and  KTable#toStream()#to  

The new Interface BytesStoreSupplier supersedes the existing StateStoreSupplier (which will remain untouched). This so we can provide a convenient way for users creating custom state stores to wrap them with caching/logging etc if they chose. In order to do this we need to force the inner most store, i.e, the custom store, to be a store of type `<Bytes, byte[]>`. 

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