arangodb/lib/Scheduler/Task.h

////////////////////////////////////////////////////////////////////////////////
/// @brief abstract base class for tasks
///
/// @file
/// Tasks are handled by the scheduler. The scheduler calls the task callback
/// as soon as a specific event occurs.
///
/// DISCLAIMER
///
/// Copyright 2004-2012 triagens GmbH, Cologne, Germany
///
/// Licensed 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.
///
/// Copyright holder is triAGENS GmbH, Cologne, Germany
///
/// @author Dr. Frank Celler
/// @author Achim Brandt
/// @author Copyright 2008-2012, triAGENS GmbH, Cologne, Germany
////////////////////////////////////////////////////////////////////////////////

#ifndef TRIAGENS_SCHEDULER_TASK_H
#define TRIAGENS_SCHEDULER_TASK_H 1

#include "Basics/Common.h"

#include "Scheduler/events.h"

namespace triagens {
  namespace rest {
    class Scheduler;

////////////////////////////////////////////////////////////////////////////////
/// @ingroup Scheduler
/// @brief abstract base class for tasks
////////////////////////////////////////////////////////////////////////////////

    class Task {
      friend class TaskManager;
      Task (Task const&);
      Task& operator= (Task const&);

      public:

////////////////////////////////////////////////////////////////////////////////
/// @brief constructs a new task
///
/// Note that the constructor has no access to the event loop. The connection
/// is provided in the method setup and any setup with regards to the event
/// loop must be done there. It is not possible to simply delete a tasks. You
/// must use the method destroy to cleanup the task, remove it from the event
/// loop and delete it. The method cleanup itself will not delete task but
/// remove it from the event loop. It is possible to use setup again to reuse
/// the task.
////////////////////////////////////////////////////////////////////////////////

        explicit
        Task (string const& name);

      public:

////////////////////////////////////////////////////////////////////////////////
/// @brief returns the task name for debugging
////////////////////////////////////////////////////////////////////////////////

        string const& getName () const {
          return name;
        }

////////////////////////////////////////////////////////////////////////////////
/// @brief returns true if task is still active
////////////////////////////////////////////////////////////////////////////////

        bool isActive () const {
          return active != 0;
        }

////////////////////////////////////////////////////////////////////////////////
/// @brief allow thread to run on slave event loop
////////////////////////////////////////////////////////////////////////////////

        virtual bool needsMainEventLoop () const;

////////////////////////////////////////////////////////////////////////////////
/// @brief called by scheduler to indicate an event
///
/// The method will only be called from within the scheduler thread, which
/// belongs to the loop parameter.
////////////////////////////////////////////////////////////////////////////////

        virtual bool handleEvent (EventToken token, EventType event) = 0;

      protected:

////////////////////////////////////////////////////////////////////////////////
/// @brief deletes a task
///
/// The method will only be called from after the task has been cleaned by
/// the method cleanup.
////////////////////////////////////////////////////////////////////////////////

        virtual ~Task ();

      protected:

////////////////////////////////////////////////////////////////////////////////
/// @brief called to set up the callback information
///
/// The method will only be called from within the scheduler thread, which
/// belongs to the loop parameter.
////////////////////////////////////////////////////////////////////////////////

        virtual bool setup (Scheduler*, EventLoop) = 0;

////////////////////////////////////////////////////////////////////////////////
/// @brief called to clear the callback information
///
/// The method will only be called from within the scheduler thread, which
/// belongs to the loop parameter.
////////////////////////////////////////////////////////////////////////////////

        virtual void cleanup () = 0;

      protected:

////////////////////////////////////////////////////////////////////////////////
/// @brief scheduler
////////////////////////////////////////////////////////////////////////////////

        Scheduler* scheduler;

////////////////////////////////////////////////////////////////////////////////
/// @brief event loop identifier
////////////////////////////////////////////////////////////////////////////////

        EventLoop loop;

      private:
        string const name;
        volatile sig_atomic_t active;
    };
  }
}

#endif