background.h

// @file background.h

/*    Copyright 2009 10gen Inc.
 *
 *    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.
 */

#pragma once

#include "concurrency/spin_lock.h"

namespace mongo {

    class BackgroundJob : boost::noncopyable {
    protected:
        explicit BackgroundJob(bool selfDelete = false);

        virtual string name() const = 0;

        virtual void run() = 0;

    public:
        enum State {
            NotStarted,
            Running,
            Done
        };

        virtual ~BackgroundJob() { }

        BackgroundJob& go();

        bool wait( unsigned msTimeOut = 0 );

        // accessors
        State getState() const;
        bool running() const;

    private:
        struct JobStatus;
        boost::shared_ptr<JobStatus> _status;  // shared between 'this' and body() thread

        void jobBody( boost::shared_ptr<JobStatus> status );

    };
    
    class PeriodicTask {
    public:
        PeriodicTask();
        virtual ~PeriodicTask();

        virtual void taskDoWork() = 0;
        virtual string taskName() const = 0;

        class Runner : public BackgroundJob {
        public:
            virtual ~Runner(){}

            virtual string name() const { return "PeriodicTask::Runner"; }
            
            virtual void run();
            
            void add( PeriodicTask* task );
            void remove( PeriodicTask* task );

        private:
            
            SpinLock _lock;
            
            // these are NOT owned by Runner
            // Runner will not delete these
            // this never gets smaller
            // only fields replaced with nulls
            vector<PeriodicTask*> _tasks;

        };

        static Runner* theRunner;

    };




} // namespace mongo

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