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.cassandra.concurrent;
  
  import org.apache.cassandra.utils.Shared;
  
  import static org.apache.cassandra.utils.Shared.Recursive.INTERFACES;
  import static org.apache.cassandra.utils.Shared.Scope.SIMULATION;
  
  /**
   * An {@link ExecutorPlus} that guarantees the order of execution matches the order of task submission,
   * and provides a simple mechanism for the recurring pattern of ensuring a job is executed at least once
   * after some point in time (i.e. ensures that at most one copy of the task is queued, with up to one
   * copy running as well)
   */
  @Shared(scope = SIMULATION, inner = INTERFACES)
  public interface SequentialExecutorPlus extends ExecutorPlus
  {
      public interface AtLeastOnceTrigger
      {
          /**
           * Ensure the job is run at least once in its entirety after this method is invoked (including any already queued)
           */
          public boolean trigger();
  
          /**
           * Run the provided task after all queued and executing jobs have completed
           */
          public void runAfter(Runnable run);
  
          /**
           * Wait until all queued and executing jobs have completed
           */
          public void sync();
      }
  
      /**
       * Return an object for orchestrating the execution of this task at least once (in its entirety) after
       * the trigger is invoked, i.e. saturating the number of pending tasks at 1 (2 including any possibly executing
       * at the time of invocation)
       */
      public AtLeastOnceTrigger atLeastOnceTrigger(Runnable runnable);
  }
  