content: /*
   * 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.direct;
  
  import org.apache.beam.sdk.Pipeline;
  import org.apache.beam.sdk.PipelineResult.State;
  import org.apache.beam.sdk.runners.AppliedPTransform;
  import org.apache.beam.sdk.transforms.PTransform;
  import org.joda.time.Duration;
  
  /**
   * An executor that schedules and executes {@link AppliedPTransform AppliedPTransforms} for both
   * source and intermediate {@link PTransform PTransforms}.
   */
  interface PipelineExecutor {
    /**
     * Starts this executor on the provided graph. The {@link RootProviderRegistry} will be used to
     * create initial inputs for the provide {@link DirectGraph graph}.
     */
    void start(DirectGraph graph, RootProviderRegistry rootProviderRegistry);
  
    /**
     * Blocks until the job being executed enters a terminal state. A job is completed after all root
     * {@link AppliedPTransform AppliedPTransforms} have completed, and all {@link CommittedBundle
     * Bundles} have been consumed. Jobs may also terminate abnormally.
     *
     * <p>Waits for up to the provided duration, or forever if the provided duration is less than or
     * equal to zero.
     *
     * @return The terminal state of the Pipeline.
     * @throws Exception whenever an executor thread throws anything, transfers to the waiting thread
     *     and rethrows it
     */
    State waitUntilFinish(Duration duration) throws Exception;
  
    /** Gets the current state of the {@link Pipeline}. */
    State getPipelineState();
  
    /**
     * Shuts down the executor.
     *
     * <p>The executor may continue to run for a short time after this method returns.
     */
    void stop();
  }
  