connection_manager.h

#ifndef _CONNECTION_MANAGER_H
#define _CONNECTION_MANAGER_H
/*
 * Fledge storage service.
 *
 * Copyright (c) 2017 OSisoft, LLC
 *
 * Released under the Apache 2.0 Licence
 *
 * Author: Mark Riddoch
 */

#include <plugin_api.h>
#include <list>
#include <mutex>
#include <thread>

class Connection;
class DiskSpaceMonitor;

class ConnectionManager {
    public:
        static ConnectionManager  *getInstance();
        void                      growPool(unsigned int);
        unsigned int              shrinkPool(unsigned int);
        Connection                *allocate();
        void                      release(Connection *);
        void              shutdown();
        void              setError(const char *, const char *, bool);
        PLUGIN_ERROR          *getError()
                      {
                        return &lastError;
                      }
        void              background();
        void              setVacuumInterval(long hours) {
                        m_vacuumInterval = 60 * 60 * hours;
                      };
        void              setPersist(bool persist, const std::string& filename = "")
                      {
                        m_persist = persist;
                        m_filename = filename;
                      }
        bool              persist() { return m_persist; };
        std::string       filename() { return m_filename; };
        void              setPurgeBlockSize(unsigned long purgeBlockSize);
    protected:
        ConnectionManager();

    private:
        static ConnectionManager     *instance;
    protected:
        std::list<Connection *>      idle;
        std::list<Connection *>      inUse;
        std::mutex                   idleLock;
        std::mutex                   inUseLock;
        std::mutex                   errorLock;
        PLUGIN_ERROR             lastError;
        bool                 m_trace;
        bool                 m_shutdown;
        std::thread          *m_background;
        long                 m_vacuumInterval;
        bool                 m_persist;
        std::string              m_filename;
        unsigned long            m_purgeBlockSize;
        DiskSpaceMonitor         *m_diskSpaceMonitor;
};

#endif