lucene/core/src/java/org/apache/lucene/search/SliceExecutor.java

/*
 * 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.lucene.search;

import java.util.Collection;
import java.util.concurrent.Executor;
import java.util.concurrent.RejectedExecutionException;

/**
 * Executor which is responsible for execution of slices based on the current status of the system
 * and current system load
 */
class SliceExecutor {
  private final Executor executor;

  public SliceExecutor(Executor executor) {
    this.executor = executor;
  }

  public void invokeAll(Collection<? extends Runnable> tasks) {

    if (tasks == null) {
      throw new IllegalArgumentException("Tasks is null");
    }

    if (executor == null) {
      throw new IllegalArgumentException("Executor is null");
    }

    int i = 0;

    for (Runnable task : tasks) {
      boolean shouldExecuteOnCallerThread = false;

      // Execute last task on caller thread
      if (i == tasks.size() - 1) {
        shouldExecuteOnCallerThread = true;
      }

      processTask(task, shouldExecuteOnCallerThread);
      ++i;
    }
    ;
  }

  // Helper method to execute a single task
  protected void processTask(final Runnable task, final boolean shouldExecuteOnCallerThread) {
    if (task == null) {
      throw new IllegalArgumentException("Input is null");
    }

    if (!shouldExecuteOnCallerThread) {
      try {
        executor.execute(task);

        return;
      } catch (RejectedExecutionException e) {
        // Execute on caller thread
      }
    }

    task.run();
  }
}