How to "lock" records in kafka streams - apache-kafka

Question

I have a stream application that reads from a topic and stores the state in a global store. There are several processors that write to the same topic by reading from the state store, updating a particular field, and writing it back to the topic.
I've noticed that some writes contain stale data and overwrites a record that was previously updated. I want to know what techniques I can use to achieve this "locking" of the records so that no processor updates the record while it is being read and processed by another. So far I believe this can be achieved by enabling exactly-once processing but would like your expert opinion on this and pointers to other things I might be missing.
streamBuilder
.addGlobalStore(
Stores
.keyValueStoreBuilder(
productGlobalState,
keySerde,
valueSerde
)
.withLoggingDisabled(),
"product-source-1",
consumedInstance,
processorSupplier
)
.stream("product-source-1")
.transform(transformer1)
.to("product-sink")
.stream("product-source-2")
.transform(transformer2)
.to("product-sink")
//state store processor
val productProcessorSupplier: ProcessorSupplier[ProductId, ProductValue] =
() =>
new AbstractProcessor[ProductId, ProductValue] {
private var store: KeyValueStore[ProductId, ProductValue] = _
override def init(context: ProcessorContext): Unit = {
super.init(context)
this.store = context
.getStateStore(ProductGlobalStoreName)
.asInstanceOf[KeyValueStore[ProductId, ProductValue]]
}
override def process(key: ProductId, value: ProductValue): Unit = {
store.put(key, value)
context().commit()
}
}
//transformer1
val transformer1: ProductTransformer =
() =>
new Transformer[
ProductId,
ProductValue,
KeyValue[ProductId, ProductValue]
] {
private var prodStore: KeyValueStore[ProductId, ProductValue] = _
override def init(context: ProcessorContext): Unit = {
this.prodStore = context
.getStateStore(ProductGlobalStoreName)
.asInstanceOf[KeyValueStore[ProductId, ProductValue]]
}
override def transform(key: ProductId, value: ProductValue): KeyValue[ProductId, ProductValue] = {
val updatedProd = Option(prodStore.get(key)).map { p =>
value.copy(isSale = p.isSale, isNew = p.isNew)//attempt to preserve these fields and not override them
} getOrElse value
KeyValue.pair(key, updatedProd)
}
override def close(): Unit = ()
}
//transformer2
val transformer2 = () => new Transformer[ProductId, ProductValue, KeyValue[ProductId, ProductValue]] {
private var context: ProcessorContext = _
protected var prodStore: KeyValueStore[ProductId, ProductValue] = _
override def init(context: ProcessorContext): Unit = {
this.context = context
this.prodStore = context
.getStateStore(ProductGlobalStoreName)
.asInstanceOf[KeyValueStore[ProductId, ProductValue]]
}
override def transform(key: ProductId, value: ProductValue): KeyValue[ProductId, ProductValue] = {
val product = prodStore.get(key)
val newValue = product.copy(product.isNew = true)
KeyValue.pair(key, newValue)
}
}
//... other transformers similar to transformer2 but updating a different fields.