pagespeed/controller/work_bound_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.
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#ifndef PAGESPEED_CONTROLLER_WORK_BOUND_EXPENSIVE_OPERATION_CONTROLLER_H_
#define PAGESPEED_CONTROLLER_WORK_BOUND_EXPENSIVE_OPERATION_CONTROLLER_H_

#include "pagespeed/controller/expensive_operation_controller.h"
#include "pagespeed/kernel/base/basictypes.h"
#include "pagespeed/kernel/base/function.h"
#include "pagespeed/kernel/base/statistics.h"

namespace net_instaweb {

// Implements ExpensiveOperationController by using a statistic to limit
// multiple simultaneous expensive jobs. Named after now removed WorkBound
// class. This uses Statistics to communicate between multiple worker
// processes so does not have have the cross-process constraints of
// QueuedExpensiveOperationController. However, this implementation does not
// queue requests, instead observing the count of in-progress operations and
// canceling the request if that number is too great.
class WorkBoundExpensiveOperationController
    : public ExpensiveOperationController {
 public:
  static const char kCurrentExpensiveOperations[];

  WorkBoundExpensiveOperationController(int max_expensive_operations,
                                        Statistics* stats);
  ~WorkBoundExpensiveOperationController() override;

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

  static void InitStats(Statistics* stats);

 private:
  bool TryToWork();

  const int bound_;
  UpDownCounter* counter_;

  DISALLOW_COPY_AND_ASSIGN(WorkBoundExpensiveOperationController);
};

}  // namespace net_instaweb

#endif  // PAGESPEED_CONTROLLER_WORK_BOUND_EXPENSIVE_OPERATION_CONTROLLER_H_