/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.beam.runners.core;
import org.apache.beam.sdk.annotations.Experimental;
import org.apache.beam.sdk.annotations.Experimental.Kind;
import org.apache.beam.sdk.state.State;
import org.apache.beam.sdk.state.StateContext;
import org.apache.beam.sdk.transforms.GroupByKey;
/**
* {@code StateInternals} describes the functionality a runner needs to provide for the
* State API to be supported.
*
* <p>The SDK will only use this after elements have been partitioned by key. For instance, after a
* {@link GroupByKey} operation. The runner implementation must ensure that any writes using
* {@link StateInternals} are implicitly scoped to the key being processed and the specific step
* accessing state.
*
* <p>The runner implementation must also ensure that any writes to the associated state objects
* are persisted together with the completion status of the processing that produced these
* writes.
*
* <p>This is a low-level API intended for use by the Beam SDK. It should not be
* used directly, and is highly likely to change.
*/
@Experimental(Kind.STATE)
public interface StateInternals {
/** The key for this {@link StateInternals}. */
Object getKey();
/**
* Return the state associated with {@code address} in the specified {@code namespace}.
*/
<T extends State> T state(StateNamespace namespace, StateTag<T> address);
/**
* Return the state associated with {@code address} in the specified {@code namespace}
* with the {@link StateContext}.
*/
<T extends State> T state(
StateNamespace namespace, StateTag<T> address, StateContext<?> c);
}