org.apache.flink.statefun.sdk.java

Interface StatefulFunction

All Known Implementing Classes:

CommandInterpreterFn

public interface StatefulFunction

A 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 StatefulFunction is an uniquely invokable "instance" of a registered StatefulFunctionSpec. Each instance is identified by an 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 StatefulFunction

An individual StatefulFunction can be invoked with arbitrary input from any another StatefulFunction (including itself), or routed from ingresses. To invoke a StatefulFunction, the caller simply needs to know the Address of the target function.

As a result of invoking a StatefulFunction, the function may continue to invoke other functions, access persisted values, or send messages to egresses.

Persistent State

Each individual 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 ValueSpec and AddressScopedStorage for an overview of how to register persistent values and access the storage.

See Also:

Address, StatefulFunctionSpec, ValueSpec, AddressScopedStorage

Method Summary

Modifier and Type	Method and Description
java.util.concurrent.CompletableFuture<java.lang.Void>	apply(Context context, Message argument) Applies an input message to this function.

Method Detail

apply

java.util.concurrent.CompletableFuture<java.lang.Void> apply(Context context,
                                                             Message argument)
                                                      throws java.lang.Throwable

Applies an input message to this function.

Parameters:

context - the Context of the current invocation.

argument - the input message.

Throws:

java.lang.Throwable