| /* |
| * 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.fnexecution.state; |
| |
| import java.util.concurrent.CompletionStage; |
| import org.apache.beam.model.fnexecution.v1.BeamFnApi.StateRequest; |
| import org.apache.beam.model.fnexecution.v1.BeamFnApi.StateResponse; |
| |
| /** |
| * Handler for {@link org.apache.beam.model.fnexecution.v1.BeamFnApi.StateRequest StateRequests}. |
| */ |
| public interface StateRequestHandler { |
| /** |
| * Handle a {@link org.apache.beam.model.fnexecution.v1.BeamFnApi.StateRequest} asynchronously. |
| * |
| * <p>The handler is allowed to complete the future within the callers thread if it can be |
| * completed without blocking. Otherwise the caller should delegate to another thread to perform |
| * any blocking work completing the future when able. |
| * |
| * <p>Throwing an error during handling will complete the handler result {@link CompletionStage} |
| * exceptionally. |
| */ |
| CompletionStage<StateResponse.Builder> handle(StateRequest request) throws Exception; |
| |
| static StateRequestHandler unsupported() { |
| return request -> { |
| throw new UnsupportedOperationException( |
| String.format("Cannot use an empty %s", StateRequestHandler.class.getSimpleName())); |
| }; |
| } |
| } |