@@ -539,7 +539,6 @@ handling yet.
|
||||
However, when you use the low-level Processor API in your application, there are options to control this behavior. See
|
||||
below.
|
||||
|
||||
|
||||
[source]
|
||||
----
|
||||
@Autowired
|
||||
@@ -579,13 +578,13 @@ public KStream<?, WordCount> process(KStream<Object, String> input) {
|
||||
|
||||
== State Store
|
||||
|
||||
State store is created automatically by Kafka Stream when Streas DSL is used. When use processor API, in case you want to
|
||||
create and register a state store manually, you can use `KafkaStreamsStateStore` annotation. You can specify store name,
|
||||
type, whether to enable log, whether disable cache, etc, and those parameters will be injected into KStream building
|
||||
process in Kafka Streams binder to create and register the store to your KStream. After that, you can access the same way
|
||||
how you access in normal Kafka Streams code.
|
||||
State store is created automatically by Kafka Streams when the DSL is used.
|
||||
When processor API is used, you need to register a state store manually. In order to do so, you can use `KafkaStreamsStateStore` annotation.
|
||||
You can specify the name and type of the store, flags to control log and disabling cache, etc.
|
||||
Once the store is created by the binder during the bootstrapping phase, you can access this state store through the processor API.
|
||||
Below are some primitives for doing this.
|
||||
|
||||
Creation code:
|
||||
Creating a state store:
|
||||
[source]
|
||||
----
|
||||
@KafkaStreamsStateStore(name="mystate", type= KafkaStreamsStateStoreProperties.StoreType.WINDOW, lengthMs=300000)
|
||||
@@ -594,7 +593,7 @@ public void process(KStream<Object, Product> input) {
|
||||
}
|
||||
----
|
||||
|
||||
Access code:
|
||||
Accessing the state store:
|
||||
[source]
|
||||
----
|
||||
Processor<Object, Product>() {
|
||||
@@ -611,14 +610,13 @@ Processor<Object, Product>() {
|
||||
|
||||
== Interactive Queries
|
||||
|
||||
As part of the public Kafka Streams binder API, we expose a class called `QueryableStoreRegistry`. You can access this
|
||||
as a Spring bean in your application. An easy way to get access to this bean from your application is to "autowire" the bean
|
||||
in your application.
|
||||
As part of the public Kafka Streams binder API, we expose a class called `InteractiveQueryService`.
|
||||
You can access this as a Spring bean in your application. An easy way to get access to this bean from your application is to "autowire" the bean.
|
||||
|
||||
[source]
|
||||
----
|
||||
@Autowired
|
||||
private QueryableStoreRegistry queryableStoreRegistry;
|
||||
private InteractiveQueryService interactiveQueryService;
|
||||
----
|
||||
|
||||
Once you gain access to this bean, then you can query for the particular state-store that you are interested. See below.
|
||||
@@ -626,5 +624,31 @@ Once you gain access to this bean, then you can query for the particular state-s
|
||||
[source]
|
||||
----
|
||||
ReadOnlyKeyValueStore<Object, Object> keyValueStore =
|
||||
queryableStoreRegistry.getQueryableStoreType("my-store", QueryableStoreTypes.keyValueStore());
|
||||
interactiveQueryService.getQueryableStoreType("my-store", QueryableStoreTypes.keyValueStore());
|
||||
----
|
||||
|
||||
If there are multiple instances of the kafka streams application running, then before you can query them interactively, you need to identify which application instance hosts the key.
|
||||
`InteractiveQueryService` API provides methods for identifying the host information.
|
||||
|
||||
In order for this to work, you must configure the property `application.server` as below:
|
||||
|
||||
[source]
|
||||
----
|
||||
spring.cloud.stream.kafka.streams.binder.configuration.application.server: <server>:<port>
|
||||
----
|
||||
|
||||
Here are some code snippets:
|
||||
|
||||
[source]
|
||||
----
|
||||
org.apache.kafka.streams.state.HostInfo hostInfo = interactiveQueryService.getHostInfo("store-name",
|
||||
key, keySerializer);
|
||||
|
||||
if (interactiveQueryService.getCurrentHostInfo().equals(hostInfo)) {
|
||||
|
||||
//query from the store that is locally available
|
||||
}
|
||||
else {
|
||||
//query from the remote host
|
||||
}
|
||||
----
|
||||
|
||||
Reference in New Issue
Block a user