flask log level is set to record only error-level and above issue

When I log in setting flask

handler = logging.FileHandler('flask.log', encoding='UTF-8')
    handler.setLevel(logging.DEBUG)
    logging_format = logging.Formatter(
        '%(asctime)s - %(levelname)s -%(pathname)s- %(filename)s - %(funcName)s - %(lineno)s - %(message)s'
    )
handler.setFormatter(logging_format)
app.logger.addHandler(handler)

flask used

from flask import current_app

@app.route('/hello')
def hell():
    current_app.logger.info('----------------info----------------')
    current_app.logger.error('----------------err----------------')
    current_app.logger.debug('----------------debug----------------')
    current_app.logger.warning('----------------warning----------------')
    return 'hello World'

Flask.log recorded in the log only error level above

2019-12-13 17:41:28,189 - ERROR -/home/frange/servers/Allocation/manage.py- manage.py - hell - 24 - ----------------err----------------
2019-12-13 17:41:28,189 - WARNING -/home/frange/servers/Allocation/manage.py- manage.py - hell - 26 - ----------------warning----------------

deal with

Before creating the app will be reset to the debug log level

logging.basicConfig(level=logging.DEBUG)