Current state: "Under Discussion"

Discussion thread: TBD here

JIRA: TBD

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

Motivation

Rich functions are one of the essential parts of stream processing. There are several use-cases where users cannot express their business logic with current un-rich methods especially when init(Some params), close() methods are needed.

Public Interfaces

KStream.java

Jira

server	ASF JIRA
serverId	5aa69414-a9e9-3523-82ec-879b028fb15b
key	KAFKA-4125

Jira

server	ASF JIRA
columns	key,summary,type,created,updated,due,assignee,reporter,priority,status,resolution
serverId	5aa69414-a9e9-3523-82ec-879b028fb15b
key	KAFKA-4218

Jira

server	ASF JIRA
columns	key,summary,type,created,updated,due,assignee,reporter,priority,status,resolution
serverId	5aa69414-a9e9-3523-82ec-879b028fb15b
key	KAFKA-4726

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

Motivation

This KIP combines KIP-149 and provides a hybrid solution to rich functions in Streams and accessing read-only keys within ValueJoiner, ValueTransformer, ValueMapper interfaces.

Rich functions are one of the essential parts of stream processing. There are several use-cases where users cannot express their business logic with current un-rich methods. For example:

having access to RecordContext within an operator
having access to a read-only key for ValueJoiner, ValueTransformer, ValueMapper interfaces

Rich Interfaces

Code Block

language	java

 
public interface RichInitializer<V, K> {
    V apply(K key);
}

public interface RichValueMapper<V, VR, K> {
    VR apply(final V value, final K key, final RecordContext recordContext);
}

public interface RichValueJoiner<V1, V2, VR, K> {
    VR apply(final V1 value1, final V2 value2, final K key, final RecordContext recordContext);
}

public interface RichKeyValueMapper<K, V, VR> {
    VR apply(final K key, final V value, final RecordContext recordContext);
}

public interface RichReducer<V, K> {
    V apply(final V value1, final V value2, final K key, final RecordContext recordContext);
}

public interface RichAggregator<K, V, VA> {
    VA apply(final K key, final V value, final VA aggregate, final RecordContext recordContext);
}
 
public interface RichForeachAction<K, V> {
    void apply(final K key, final V value, final RecordContext recordContext);
}

public interface RichPredicate<K, V> {
    boolean test(final K key, final V value, final RecordContext recordContext);
}

 
public interface RichMerger<K, V> {
	V apply(final K aggKey, final V aggOne, final V aggTwo, final RecordContext recordContext);
}

 
 
public interface RichValueTransformer<V, VR, K> {
	void init(final ProcessorContext context);

	VR transform(final V value, final K key);

	void close();
}


 
public interface RichValueTransformerSupplier<V, VR, K> {

    RichValueTransformer<V, VR, K> get();
}

Public Interfaces

KStream

Code Block

language	java

KStream<K, V> filter(RichPredicate<

Code Block

language	java

KStream<K, V> filter(RichPredicate<? super K, ? super V> predicate);


KStream<K, V> filterNot(RichPredicate<? super K, ? super V> predicate);


<KR> KStream<KR, V> selectKey(RichKeyValueMapper<? super K, ? super V, ? extends KR> mapper);


<KR, VR> KStream<KR, VR> map(RichKeyValueMapper<? super K, ? super V, ? extends KeyValue<? extends KR, ? extends VR>> mapper);


<VR> KStream<K, VR> mapValues(RichValueMapper<? super V, ? extends VR> mapper);


<KR, VR> KStream<KR, VR> flatMap(final RichKeyValueMapper<? super K, ? super V, ? extends Iterable<? extends KeyValue<? extends KR, ? extends VR>>> mapper);


<VR> KStream<K, VR> flatMapValues(final RichValueMapper<? super V, ? extends Iterable<? extends VR>> processor);


void foreach(final RichForeachAction<? super K, ? super V> action);


KStream<K, V> peek(final RichForeachAction<? super K, ? super V> actionpredicate);


KStream<K, V>[] branchfilterNot(final RichPredicate<? super K, ? super V>... predicatespredicate);


<KR> KGroupedStream<KRKStream<KR, V> groupByselectKey(final RichKeyValueMapper<? super K, ? super V, ? extends KR> selectormapper);


<KR> KGroupedStream<KR<KR, VR> KStream<KR, V>VR> groupBymap(final RichKeyValueMapper<? super K, ? super V, KR>? selector,
extends KeyValue<? extends KR, ? extends                              final Serde<KR> keySerde,
                                   final Serde<V> valSerde);


<VO, VR> KStream<K, VR> join(final KStream<K, VO> otherStream,
                             final RichValueJoiner<VR>> mapper);
<VR> KStream<K, VR> mapValues(RichValueMapper<? super V, ? extends VR, ? super K> mapper);
<KR, VR> KStream<KR, VR> flatMap(final RichKeyValueMapper<? super K, ? super V, ? extends Iterable<? extends KeyValue<? extends KR, ? extends VR>>> mapper);
 
<VR> KStream<K, VR> flatMapValues(final RichValueMapper<? super V, ? extends Iterable<? extends VR>, ? super K> mapper);



void foreach(final RichForeachAction<? super K, ? super V> action);
KStream<K, V> peek(final RichForeachAction<? super K, ? super V> action);
KStream<K, V>[] branch(final RichPredicate<? super K, ? super V>... predicates);
 
<VR> KStream<K, VR> transformValues(final RichValueTransformerSupplier<? super V, ? superextends VOVR, ? extendssuper VR>K> joinervalueTransformerSupplier,
                             final  JoinWindows windows);


<VO, VR> KStream<K, VR> join(final KStream<K, VO> otherStream,
                             final RichValueJoiner<? super VString... stateStoreNames);
<KR> KGroupedStream<KR, V> groupBy(final RichKeyValueMapper<? super K, ? super V, KR> selector);
<KR> KGroupedStream<KR, V> groupBy(final RichKeyValueMapper<? super K, ? super VOV, ? extends VR> joinerKR> selector,
                             final JoinWindows windows,
    final Serialized<KR, V> serialized);
 

<VO, VR> KStream<K, VR> join(final KStream<K, VO> otherStream,
               final Serde<K> keySerde,
                             final Serde<V> thisValueSerdefinal RichValueJoiner<? super V, ? super VO, ? extends VR, ? super K> joiner,
                             final Serde<VO>JoinWindows otherValueSerdewindows);


<VO, VR> KStream<K, VR> leftJoinjoin(final KStream<K, VO> otherStream,
                                 final RichValueJoiner<? super V, ? super VO, ? extends VR> joinerVR,
 ? super                               final JoinWindows windows);


<VO, VR> KStream<K, VR> leftJoin(final KStream<K, VO> otherStream,
K> joiner,
                             final JoinWindows windows,
         final RichValueJoiner<? super V, ? super VO, ? extends VR> joiner,
          final Joined<K, V, VO> joined);
 

<VO, VR> KStream<K, VR> leftJoin(final KStream<K, VO> otherStream,
               final JoinWindows windows,
                final RichValueJoiner<? super V, ? super VO, ? extends VR, ? super K> joiner,
    final Serde<K> keySerde,
                           final JoinWindows windows);
<VO, VR> KStream<K, VR> leftJoin(final Serde<V> thisValSerdeKStream<K, VO> otherStream,
                                 final Serde<VO> otherValueSerde);


<VO, VR> KStream<K, VR> outerJoin(final KStream<K, VO> otherStream,
        RichValueJoiner<? super V, ? super VO, ? extends VR, ? super K> joiner,
                          final RichValueJoiner<? super V, ? super VO, ? extendsfinal VR>JoinWindows joinerwindows,
                                 final Joined<K, finalV, JoinWindowsVO> windowsjoined);
 

<VO, VR> KStream<K, VR> outerJoin(final KStream<K, VO> otherStream,
                                  final RichValueJoiner<? super V, ? super VO, ? extends VR> VR, ? super K> joiner,
                                  final JoinWindows windows);
<VO, VR> KStream<K, VR> outerJoin(final KStream<K, VO> otherStream,
                                  final RichValueJoiner<? super V, ? super VO, ? extends VR, ? finalsuper Serde<K>K> keySerdejoiner,
                                  final Serde<V>JoinWindows thisValueSerdewindows,
                                  final Serde<VO> otherValueSerde Joined<K, V, VO> joined);
 

<VT, VR> KStream<K, VR> join(final KTable<K, VT> table,
                             final RichValueJoiner<? super K, ? super V, ? super VT, ? extends VR> joiner);


<VT, VR> KStream<K, VR> join(final KTable<K, VT> table,
                             final RichValueJoiner<? super V, ? super VT, ? extends VR> joiner,
                             final Serde<K> keySerde K, ? super V, ? super VT, ? extends VR> joiner,
                             final Serde<V> valSerde Joined<K, V, VT> joined);
 

<VT, VR> KStream<K, VR> leftJoin(final KTable<K, VT> table,
                                 final RichValueJoiner<? super K, ? super V, ? super VT, ? extends VR> joiner);


<VT, VR> KStream<K, VR> leftJoin(final KTable<K, VT> table,
                                 final RichValueJoiner<? super VK, ? super VT, ? extends VR> joiner,
                                 final Serde<K> keySerdeV, ? super VT, ? extends VR> joiner,
                                 final Serde<V> valSerde Joined<K, V, VT> joined);
 

<GK, GV, RV> KStream<K, RV> join(final GlobalKTable<GK, GV> globalKTable,
                                 final RichKeyValueMapper<? super K, ? super V, ? extends GK> keyValueMapper,
                                 final RichValueJoiner<? super K, ? super V, ? super GV, ? extends RV> joiner);


<GK, GV, RV> KStream<K, RV> leftJoin(final GlobalKTable<GK, GV> globalKTable,
                                     final RichKeyValueMapper<? super K, ? super V, ? extends GK> keyValueMapper,
                                     final RichValueJoiner<? super K, ? super V, ? super GV, ? extends RV> valueJoiner);

KTable

...

Code Block

language	java

KTable<K, V> filter(final RichPredicate<? super K, ? super V> predicate);


KTable<K, V> filter(final RichPredicate<? super K, ? super V> predicate, final String queryableStoreName);


KTable<K, V> filter(final RichPredicate<? super K, ? super V> predicate, final StateStoreSupplier<KeyValueStore> storeSupplier);



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


KTable<K, V> filterNot(final RichPredicate<? super K, ? super V> predicate,
      final StateStoreSupplier<KeyValueStore> storeSupplier);


KTable<K, V> filterNot(final RichPredicate<? super K, ? super V> predicate, final String queryableStoreName);


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


<VR> KTable<K, VR> mapValues(final RichValueMapper<? super V, ? extends VR> mapperVR, final? Serde<VR>super valueSerde, final String queryableStoreNameK> mapper);


<VR> KTable<K, VR> mapValues(final RichValueMapper<? super V, ? extends VR> mapperVR,
 ? super                           final Serde<VR> valueSerdeK> mapper,
                             final StateStoreSupplier<KeyValueStore> storeSupplier);


void foreach(final RichForeachAction<? super K, ? super V> action final Materialized<K, VR, KeyValueStore<Bytes, byte[]>> materialized);


<KR> KStream<KR, V> toStream(final RichKeyValueMapper<? super K, ? super V, ? extends KR> mapper);
 

<KR, VR> KGroupedTable<KR, VR> groupBy(final RichKeyValueMapper<? super K, ? super V, KeyValue<KR, VR>> selector);


<KR, VR> KGroupedTable<KR, VR> groupBy(final RichKeyValueMapper<? super K, ? super V, KeyValue<KR, VR>> selector,
                                       final Serde<KR> keySerdeSerialized<KR,
                                       final Serde<VR> valueSerdeVR> serialized);
 

<VO, VR> KTable<K, VR> join(final KTable<K, VO> other,
                            final RichValueJoiner<? super V, ? super VO, ? extends VR, ? extendssuper VR>K> joiner);


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

<VO, VR> KTable<K, VR> leftJoin(final KTable<K, VO> other,
                                final RichValueJoiner<? super V, ? super VO, ? extends VR, ? super finalK> String queryableStoreNamejoiner);


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

<VO, VR> KTable<K, VR> leftJoinouterJoin(final KTable<K, VO> other,
                                 final RichValueJoiner<? super V, ? super VO, ? extends VR>VR, ? super K> joiner);

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

KGroupedStream

Code Block

language	java

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

KTable<K, V> reduce(final RichReducer<V, K> reducer,
                    final  final String queryableStoreNameMaterialized<K, V, KeyValueStore<Bytes, byte[]>> materialized);

<VO, VR><VR> KTable<K, VR> leftJoinaggregate(final KTable<KRichInitializer<VR, VO>K> otherinitializer,
                                final RichValueJoiner<RichAggregator<? super VK, ? super VOV, ? extends VR> joineraggregator,
                             final Materialized<K, VR, final StateStoreSupplier<KeyValueStore> storeSupplierKeyValueStore<Bytes, byte[]>> materialized);

<VO,<VR> VR> KTable<K, VR> outerJoinaggregate(final KTable<KRichInitializer<VR, VO>K> otherinitializer,
                                 final RichValueJoiner<RichAggregator<? super VK, ? super VO, ? extends V, VR> aggregator);

SessionWindowedKStream

There are 3 rich interfaces in aggregate() methods. So converting all possible combinations to their rich counterparts can cause a lot of overloads. So, I propose to overload one method with all rich interfaces.

Code Block

language	java

<T> KTable<Windowed<K>, T> aggregate(final RichInitializer<T, Windowed<K>> initializer,
  joiner);

<VO, VR> KTable<K, VR> outerJoin(final KTable<K, VO> other,
                                   final RichValueJoiner<RichAggregator<? super VK, ? super VOV, ? extends VR> joinerT> aggregator,
                                 final Serde<VR> joinSerde,
  final RichMerger<? super K, T> sessionMerger);
<VR> KTable<Windowed<K>, VR> aggregate(final RichInitializer<VR, Windowed<K>> initializer,
                    final String queryableStoreName);

<VO, VR> KTable<K, VR> outerJoin(final KTable<K, VO> other,
          final RichAggregator<? super K, ? super V, VR> aggregator,
               final RichValueJoiner<? super V, ? super VO, ? extends VR> joiner,
              final RichMerger<? super K, VR> sessionMerger,
              final StateStoreSupplier<KeyValueStore> storeSupplier);

Limiting the ProcessorContext - RecordContext interface

We create a subset of features from ProcessorContext and put into RecordContext interface

Code Block

language	java

public interface RecordContext {
    String applicationId();
    TaskId taskId();
    StreamsMetrics metrics();
    String topic();
    int partition();
	void commit();
    long offset();final Materialized<K, VR, SessionStore<Bytes, byte[]>> materialized);

KTable<Windowed<K>, V> reduce(final RichReducer<V, K> reducer);
KTable<Windowed<K>, V> reduce(final RichReducer<V, K> reducer,
    long timestamp();
    Map<String, Object> appConfigs();
       Map<String, Object> appConfigsWithPrefix(String prefix);
}
 
 
public interface ProcessorContext extends RecordContext {
   // all methodsfinal butMaterialized<K, theV, ones in RecordContext
}

Once we need a conversion from ProcessorContext and RecordContext, we just cast:

SessionStore<Bytes, byte[]>> materializedAs);


,

TimeWindowedKStream

Code Block

language	java

private class KStreamMapProcessor extends AbstractProcessor<K, V> {
 
<VR> KTable<Windowed<K>, VR> aggregate(final RichInitializer<VR, K> initializer,
       @Override
    public void init(ProcessorContext processorContext) {
        super.init(processorContext);
        richMapper.init((RecordContext) processorContext);  				// HERE WE MAKE A CAST
final RichAggregator<? super K, }

? super V, VR> @Overrideaggregator);
<VR> KTable<Windowed<K>,   public void processVR> aggregate(final K key, final V value) {
RichInitializer<VR, K> initializer,
            V1 newValue = mapper.apply(key, value);
        context().forward(key, newValue);
    }

    @Override
    public void close() {
        super.close();final RichAggregator<? super K, ? super V, VR> aggregator,
        mapper.close();
    }
}

Rich Interfaces

Code Block

language	java

public interface RichValueMapper<V, VR> {
    VR apply(final V value, final RecordContext recordContext);
}

public interface RichValueJoiner<V1, V2, VR> {
    VR apply(final V1 value1, final V2 value2, final RecordContext recordContextMaterialized<K, VR, WindowStore<Bytes, byte[]>> materialized);
}

publicKTable<Windowed<K>, interface RichKeyValueMapper<K, VV> reduce(final RichReducer<V, VR>K> {reducer);
KTable<Windowed<K>, V>   VR applyreduce(final K keyRichReducer<V, finalK> V valuereducer,
 final RecordContext recordContext);
}

public interface RichReducer<V> {
    V apply(final V value1, final V value2, final RecordContext recordContext);
}


public interface RichInitializer<VA> {
           VA apply(final RecordContext recordContext);
}


public interface Aggregator<K, V, VA> {
    VA apply(final K key, final V value, final VA aggregate, final RecordContext recordContext);
}
 
public interface RichForeachAction<K, V> {
    void apply(final K key, final V value, final RecordContext recordContext);
}


public interface RichPredicate<K, V> {
    boolean test(final K key, final V value, final RecordContext recordContext);
}

The same semantics apply to other interfaces as well.

So we don't need to add any overloaded methods for public APIs. Internally we perform 2 changes:

Change the constructor type of all related Processors to accept rich interfaces
Create converters from non-rich to rich interfaces

final Materialized<K, V, WindowStore<Bytes, byte[]>> materialized);

KGroupedTable

Code Block

language	java

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

KTable<K, V> reduce(final RichReducer<V, K> adder,
                    final RichReducer<V, K> subtractor);

<VR> KTable<K, VR> aggregate(final RichInitializer<VR> initializer,
                             final RichAggregator<? super K, ? super V, VR> adder,

Code Block

language	java

class KStreamMapValues<K, V, V1> implements ProcessorSupplier<K, V> {

    private final RichValueMapper<K, V, V1> mapper;

    public KStreamMapValues(RichValueMapper<K, V, V1> mapper) {
        this.mapper = mapper;
    }

    @Override
    public Processor<K, V> get() {
        return new KStreamMapProcessor();
    }

  final RichAggregator<? privatesuper classK, KStreamMapProcessor? extendssuper AbstractProcessor<KV, V>VR> {subtractor,
        @Override
          public void init(ProcessorContext processorContext) {
       final Materialized<K, VR, KeyValueStore<Bytes,  super.init(processorContextbyte[]>> materialized);
<VR> KTable<K, VR> aggregate(final RichInitializer<VR> initializer,
        mapper.init((RecordContext) processorContext);
        }

        @Override
    final RichAggregator<? super K, public? void process(final K key, final V value) {
super V, VR> adder,
                     V1 newValue = mapper.apply(key, value);
    final RichAggregator<? super K, ? super V, VR> subtractor);

Proposed changes

Move RecordContext from .processor.internals to .processor

Make record context open to public

Currently we set record context through InternalProcessorContext (StreamTask.updateProcessorContext()) :

Code Block

language	java

// the below code snippet already exists, this is just for background. 
private void updateProcessorContext(final StampedRecord record, final ProcessorNode currNode().forward(key, newValue);
        }

        @Override
        public void close() {
    processorContext.setRecordContext(new        super.close(ProcessorRecordContext(record.timestamp, record.offset(), record.partition(), record.topic()));
            mapper.close(processorContext.setCurrentNode(currNode);
}

Sample processor should look like this:

Code Block

language	java

class KStreamKTableJoinProcessor<K1, K2, V1, V2, R> extends AbstractProcessor<K1, V1> {

    ...        }
    }
}
 
 
 
 
 
static <K, T1, T2, R> RichValueJoiner<K, T1, T2, R> convertToRichValueJoiner(final ValueJoinerWithKey<K, T1, T2, R> valueJoinerWithKey) {
    Objects.requireNonNull(valueJoinerWithKey, "valueJoiner can't be null");
    ifprivate (valueJoinerWithKeyRecordContext instanceofrecordContext; RichValueJoiner) {
        return (RichValueJoiner<K, T1, T2, R>) valueJoinerWithKey;
    } else {
  // this line is added in this KIP

    ...

    @Override
	public void returnprocess(final newK1 RichValueJoiner<Kkey, T1,final T2,V1 R>(value) {

    	recordContext = new RecordContext() {    @Override
           // publicrecordContext voidinitialization init() {}

        is added in this KIP

    		@Override
    		public long offset() {
       public void close() {		return context().recordContext().offset();
    		}

    		@Override
    		public long timestamp()  @Override{
        		return context().recordContext().timestamp();
   public R apply(K key, T1 value1, T2 value2) { 		}

    		@Override
    		public String topic() {
         		return valueJoinerWithKey.apply(key, value1, value2context().recordContext().topic();
            		}

        };		@Override
    }
}

static <K, T1, T2, R> ValueJoinerWithKey<K, T1, T2, R> convertToValueJoinerWithKey(final ValueJoiner<T1, T2, R> valueJoiner) {
    Objects.requireNonNull(valueJoiner, "valueJoiner can't be null");
    return new ValueJoinerWithKey<K, T1, T2, R>() {
		public int partition() {
        		return context().recordContext().partition();
    		}
      };

	
 
    if (key != null && value != null) {
        final @Override
V2 value2 = valueGetter.get(keyMapper.apply(key, value));
    public R apply(K key, T1if value1, T2(leftJoin || value2 != null) {
            return valueJoinercontext().forward(key, joiner.apply(value1value, value2, recordContext));    
        }
    };
}




}

Rejected Alternatives

Not yet.

Space shortcuts

Child pages

Versions Compared

Old Version 10

New Version Current

Key

Motivation

Public Interfaces

`KStream.java`

Motivation

Rich Interfaces

Public Interfaces

KStream

KTable

KGroupedStream

SessionWindowedKStream

Limiting the ProcessorContext - RecordContext interface

TimeWindowedKStream

Rich Interfaces

KGroupedTable

Proposed changes

Move `RecordContext` from `.processor.internals` to `.processor`

Make record context open to public

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Child pages

Page History

Versions Compared

Old Version 10

New Version Current

Key

Motivation

Public Interfaces

KStream.java

Motivation

Rich Interfaces

Public Interfaces

KStream

KTable

KGroupedStream

SessionWindowedKStream

Limiting the ProcessorContext - RecordContext interface

TimeWindowedKStream

Rich Interfaces

KGroupedTable

Proposed changes

Move RecordContext from .processor.internals to .processor

Make record context open to public

`KStream.java`

Move `RecordContext` from `.processor.internals` to `.processor`