pagespeed/controller/queued_expensive_operation_controller.h

/*
 * 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.
 */

#ifndef PAGESPEED_CONTROLLER_QUEUED_EXPENSIVE_OPERATION_CONTROLLER_H_
#define PAGESPEED_CONTROLLER_QUEUED_EXPENSIVE_OPERATION_CONTROLLER_H_

#include <queue>

#include "pagespeed/controller/expensive_operation_controller.h"
#include "pagespeed/kernel/base/abstract_mutex.h"
#include "pagespeed/kernel/base/basictypes.h"
#include "pagespeed/kernel/base/function.h"
#include "pagespeed/kernel/base/scoped_ptr.h"
#include "pagespeed/kernel/base/statistics.h"
#include "pagespeed/kernel/base/thread_annotations.h"
#include "pagespeed/kernel/base/thread_system.h"

namespace net_instaweb {

// Implements ExpensiveOperationController using a counter and a queue to
// limit operations in strict order. Note that this implementation does not
// communicate across process boundaries; It assumes that requests from all
// workers will be routed to it either by virtue of running in a single
// process/multi-threaded environment, or through an external RPC system.
// See WorkBoundExpensiveOperationController for an alternate implementation
// that does not have this limitation.
class QueuedExpensiveOperationController : public ExpensiveOperationController {
 public:
  static const char kActiveExpensiveOperations[];
  static const char kQueuedExpensiveOperations[];
  static const char kPermittedExpensiveOperations[];

  QueuedExpensiveOperationController(int max_expensive_operations,
                                     ThreadSystem* thread_system,
                                     Statistics* stats);
  ~QueuedExpensiveOperationController() override;

  // ExpensiveOperationController interface.
  void ScheduleExpensiveOperation(Function* callback) override;
  void NotifyExpensiveOperationComplete() override;

  static void InitStats(Statistics* stats);

 private:
  void IncrementInProgress() EXCLUSIVE_LOCKS_REQUIRED(mutex_);
  void DecrementInProgress() EXCLUSIVE_LOCKS_REQUIRED(mutex_);

  void Enqueue(Function* function) EXCLUSIVE_LOCKS_REQUIRED(mutex_);
  Function* Dequeue() EXCLUSIVE_LOCKS_REQUIRED(mutex_);

  const int max_in_progress_;
  std::queue<Function*> queue_ GUARDED_BY(mutex_);
  int num_in_progress_ GUARDED_BY(mutex_);
  std::unique_ptr<AbstractMutex> mutex_;
  UpDownCounter* active_operations_counter_;
  UpDownCounter* queued_operations_counter_;
  TimedVariable* permitted_operations_counter_;

  DISALLOW_COPY_AND_ASSIGN(QueuedExpensiveOperationController);
};

}  // namespace net_instaweb

#endif  // PAGESPEED_CONTROLLER_QUEUED_EXPENSIVE_OPERATION_CONTROLLER_H_