MXS-1775 Add functions for checking disk space of servers

include/maxscale/monitor.h

@@ -230,6 +230,7 @@ typedef struct monitored_server
     uint64_t mon_prev_status;       /**< Status before starting the current monitor loop */
     uint64_t pending_status;        /**< Status during current monitor loop */
     bool new_event;                 /**< Whether an action was taken on the last event */
+    int64_t disk_space_checked;     /**< When was the disk space checked the last time */
     struct monitored_server *next;  /**< The next server in the list */
 } MXS_MONITORED_SERVER;
 

include/maxscale/monitor.hh

@@ -113,6 +113,12 @@ protected:
         return atomic_load_int32(&m_shutdown) != 0;
     }
 
+    bool should_check_disk_space(const MXS_MONITORED_SERVER* pMonitored_server) const;
+
+    void check_disk_space(MXS_MONITORED_SERVER* pMonitored_server);
+
+    static int64_t get_time_ms();
+
     /**
      * @brief Configure the monitor.
      *