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.dataflow.worker.util.common.worker;
  
  import java.util.List;
  import org.apache.beam.runners.dataflow.worker.counters.CounterSet;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Lists;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /** Abstract executor for WorkItem tasks. */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public interface WorkExecutor extends AutoCloseable {
  
    /** Returns the set of output counters for this task. */
    CounterSet getOutputCounters();
  
    /** Executes the task. */
    public abstract void execute() throws Exception;
  
    /**
     * Returns the worker's current progress.
     *
     * <p>May be called at any time, but generally called concurrently to execute().
     */
    default NativeReader.Progress getWorkerProgress() throws Exception {
      // By default, return null indicating worker progress not available.
      return null;
    }
  
    /** See {@link NativeReader.NativeReaderIterator#requestCheckpoint}. */
    default NativeReader.@Nullable DynamicSplitResult requestCheckpoint() throws Exception {
      // By default, checkpointing does nothing.
      return null;
    }
  
    /**
     * See {@link NativeReader.NativeReaderIterator#requestDynamicSplit}. Makes sense only for tasks
     * that read input.
     */
    default NativeReader.@Nullable DynamicSplitResult requestDynamicSplit(
        NativeReader.DynamicSplitRequest splitRequest) throws Exception {
      // By default, dynamic splitting is unsupported.
      return null;
    }
  
    @Override
    default void close() {
      // By default, nothing to close or shut down.
    }
  
    /**
     * Requests that the executor abort as soon as possible.
     *
     * <p>Thread-safe. May be called at any time after execute() begins.
     */
    default void abort() {
      // By default, does nothing. Expensive operations should override this.
    }
  
    /**
     * Reports the sink index of any WriteOperation that did not produce output. NOTE this is only
     * used for FlumeWriteOperaton for now.
     */
    default List<Integer> reportProducedEmptyOutput() {
      return Lists.newArrayList();
    }
  }
  