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.kafka.streams.processor.internals.tasks;
  
  import org.apache.kafka.common.KafkaFuture;
  import org.apache.kafka.streams.processor.internals.ReadOnlyTask;
  import org.apache.kafka.streams.processor.internals.StreamTask;
  
  import java.time.Duration;
  
  public interface TaskExecutor {
  
      /**
       * @return ID name string of the task executor.
       */
      String name();
  
      /**
       * Starts the task executor.
       * Idempotent operation - will have no effect if thread is already started.
       */
      void start();
  
      /**
       * Returns true if the task executor thread is running.
       */
      boolean isRunning();
  
      /**
       * Asks the task executor to shut down.
       * Idempotent operation - will have no effect if thread was already asked to shut down
       *
       * @throws
       *     org.apache.kafka.streams.errors.StreamsException if the state updater thread cannot shutdown within the timeout
       */
      void requestShutdown();
  
      /**
       * Shuts down the task processor updater.
       * Idempotent operation - will have no effect if thread is already shut down.
       * Must call `requestShutdown` first.
       *
       * @param timeout duration how long to wait until the state updater is shut down
       *
       * @throws
       *     org.apache.kafka.streams.errors.StreamsException if the state updater thread does not shutdown within the timeout
       */
      void awaitShutdown(final Duration timeout);
  
      /**
       * Get the current assigned processing task. The task returned is read-only and cannot be modified.
       *
       * @return the current processing task
       */
      ReadOnlyTask currentTask();
  
      /**
       * Unassign the current processing task from the task processor and give it back to the state manager.
       *
       * Note there is an asymmetry between assignment and unassignment between {@link TaskManager} and {@link TaskExecutor},
       * since assigning a task from task manager to task executor is always initiated by the task executor itself, by calling
       * {@link TaskManager#assignNextTask(TaskExecutor)},
       * while unassigning a task and returning it to task manager could be triggered either by the task executor proactively
       * when it finds the task not processable anymore, or by the task manager when it needs to commit / close it.
       * This function is used for the second case, where task manager will call this function asking the task executor
       * to give back the task.
       *
       * The task must be flushed before being unassigned, since it may be committed or closed by the task manager next.
       *
       * This method does not block, instead a future is returned; when the task executor finishes
       * unassigning the task this future will then complete.
       *
       * @return the future capturing the completion of the unassign process
       */
      KafkaFuture<StreamTask> unassign();
  }
  