org.apache.flink.statefun.sdk.java.StatefulFunction Maven / Gradle / Ivy
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*
* http://www.apache.org/licenses/LICENSE-2.0
*
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package org.apache.flink.statefun.sdk.java;
import java.util.concurrent.CompletableFuture;
import org.apache.flink.statefun.sdk.java.message.Message;
/**
* A {@link StatefulFunction} is a user-defined function that can be invoked with a given input.
* This is the primitive building block for a Stateful Functions application.
*
* Concept
*
* Each individual {@code StatefulFunction} is an uniquely invokable "instance" of a registered
* {@link StatefulFunctionSpec}. Each instance is identified by an {@link Address}, representing the
* function's unique id (a string) within its type. From a user's perspective, it would seem as if
* for each unique function id, there exists a stateful instance of the function that is always
* available to be invoked within a Stateful Functions application.
*
*
Invoking a {@code StatefulFunction}
*
* An individual {@code StatefulFunction} can be invoked with arbitrary input from any another
* {@code StatefulFunction} (including itself), or routed from ingresses. To invoke a {@code
* StatefulFunction}, the caller simply needs to know the {@code Address} of the target function.
*
*
As a result of invoking a {@code StatefulFunction}, the function may continue to invoke other
* functions, access persisted values, or send messages to egresses.
*
*
Persistent State
*
* Each individual {@code StatefulFunction} may have persistent values written to storage that is
* maintained by the system, providing consistent exactly-once and fault-tolerant guarantees. Please
* see Javadocs in {@link ValueSpec} and {@link AddressScopedStorage} for an overview of how to
* register persistent values and access the storage.
*
* @see Address
* @see StatefulFunctionSpec
* @see ValueSpec
* @see AddressScopedStorage
*/
public interface StatefulFunction {
/**
* Applies an input message to this function.
*
* @param context the {@link Context} of the current invocation.
* @param argument the input message.
*/
CompletableFuture apply(Context context, Message argument) throws Throwable;
}