trove upgrade 用于将数据库从一个版本更新到另一个版本，如：将mysql5.5更换到mysql5.6

trove/taskmanager/manager.py 368行

    def upgrade(self, context, instance_id, datastore_version_id):
        instance_tasks = models.BuiltInstanceTasks.load(context, instance_id)
        datastore_version = DatastoreVersion.load_by_uuid(datastore_version_id)
        with EndNotification(context):
            instance_tasks.upgrade(datastore_version)

instance_tasks.upgrade(datastore_version)调用

trove/taskmanager/models.py 1501行

    def upgrade(self, datastore_version):
    ...
        try:
            upgrade_info = self.guest.pre_upgrade()
    ...
            self.server.rebuild(datastore_version.p_w_picpath_id,
                                files=injected_files)
    ...
            if volume:
                upgrade_info['device'] = volume_device

            self.guest.post_upgrade(upgrade_info)

            self.reset_task_status()
    ...

upgrade instance 主要是以下几步完成：

• self.guest.pre_upgrade：更新前的一些操作，主要是将mysql的配置文件保存在cinder volume中

• self.server.rebuild：用新的数据库基础镜像重建trove的nova实例

• self.guest.post_upgrade：重建nova instance後的一些操作，主要操作是从cinder volume中恢复mysql配置文件，启动mysql

self.guest.pre_upgrade，self.guest.post_upgrade 通过rcp方式调用运行在nova instance上的trove-guestagent的中对应方法

trove/guestagent/datastore/mysql/_common/manager.py 245行

    def pre_upgrade(self, context):
        app = self.mysql_app(self.mysql_app_status.get())
        data_dir = app.get_data_dir()
        mount_point, _data = os.path.split(data_dir)
        save_dir = "%s/etc_mysql" % mount_point
        save_etc_dir = "%s/etc" % mount_point
        home_save = "%s/trove_user" % mount_point

        app.status.begin_restart()
        app.stop_db()

        if operating_system.exists("/etc/my.cnf", as_root=True):
            operating_system.create_directory(save_etc_dir, as_root=True)
            operating_system.copy("/etc/my.cnf", save_etc_dir,
                                  preserve=True, as_root=True)

        operating_system.copy("/etc/mysql/.", save_dir,
                              preserve=True, as_root=True)

        operating_system.copy("%s/." % os.path.expanduser('~'), home_save,
                              preserve=True, as_root=True)

        self.unmount_volume(context, mount_point=data_dir)
        return {
            'mount_point': mount_point,
            'save_dir': save_dir,
            'save_etc_dir': save_etc_dir,
            'home_save': home_save
        }

pre_upgrade备份数据库的配置文件、guestagent位于trove home 目录下的配置信息，返回包含备份信息的一个字典

trove/guestagent/datastore/mysql/_common/manager.py 275行

    def post_upgrade(self, context, upgrade_info):
        app = self.mysql_app(self.mysql_app_status.get())
        app.stop_db()
        if 'device' in upgrade_info:
            self.mount_volume(context, mount_point=upgrade_info['mount_point'],
                              device_path=upgrade_info['device'],
                              write_to_fstab=True)

        if operating_system.exists(upgrade_info['save_etc_dir'],
                                   is_directory=True, as_root=True):
            operating_system.copy("%s/." % upgrade_info['save_etc_dir'],
                                  "/etc", preserve=True, as_root=True)

        operating_system.copy("%s/." % upgrade_info['save_dir'], "/etc/mysql",
                              preserve=True, as_root=True)
        operating_system.copy("%s/." % upgrade_info['home_save'],
                              os.path.expanduser('~'),
                              preserve=True, as_root=True)
        self.configuration_manager.refresh_cache()
        app.start_mysql()

post_upgrade恢复备份中的配置文件，不对老数据库的任何文件作修改，直接使用老数据库的配置文件与数据文件启动数据库