How to add a custom StateStore to the Kafka Streams DSL processor?

Question

For one of my Kafka streams apps, I need to use the features of both DSL and Processor API. My streaming app flow is

source -> selectKey -> filter -&g         


        

Answer 1

You need to register you store outside of you processor using StreamsBuilder (or KStreamBuilder in older releases). First you create the store, than you registers it to StreamsBuilder (KStreamBuilder), and when you add the processor you provide the store name to connect the processor and the store.

StreamsBuilder builder = new StreamsBuilder();

// create store
StoreBuilder storeBuilder = Stores.keyValueStoreBuilder(
    Stores.persistentKeyValueStore("invStore"),
    Serdes.String(),
    invSerde));
// register store
builder.addStateStore(storeBuilder);

KStream<String, String> source = builder.stream(source_stream);
source.selectKey(new MyKeyValueMapper())
        .filterNot((k,v) -> k.equals("UnknownGroup"))
        .process(() -> new MyProcessor(), "invStore"); // connect store to processor by providing store name


// older API:

KStreamBuilder builder = new KStreamBuilder();

// create store
StateStoreSupplier storeSupplier = (KeyValueStore)Stores.create("invStore")
    .withKeys(Serdes.String())
    .withValues(invSerde)
    .persistent()
    .build();
// register store
builder.addStateStore(storeSupplier);

KStream<String, String> source = builder.stream(source_stream);
source.selectKey(new MyKeyValueMapper())
        .filterNot((k,v) -> k.equals("UnknownGroup"))
        .process(() -> new MyProcessor(), "invStore"); // connect store to processor by providing store name