Python django.db.connection 模块，is_usable() 实例源码

def check_database_connected(app_configs, **kwargs):
    """
    A Django check to see if connecting to the configured default
    database backend succeeds.
    """
    errors = []

    try:
        connection.ensure_connection()
    except OperationalError as e:
        msg = 'Could not connect to database: {!s}'.format(e)
        errors.append(checks.Error(msg, id=ERROR_CANNOT_CONNECT_DATABASE))
    except ImproperlyConfigured as e:
        msg = 'Datbase misconfigured: "{!s}"'.format(e)
        errors.append(checks.Error(msg, id=ERROR_MISCONFIGURED_DATABASE))
    else:
        if not connection.is_usable():
            errors.append(checks.Error('Database connection is not usable',
                                       id=ERROR_UNUSABLE_DATABASE))

    return errors

def _should_check_constraints(self, connection):
        return (
            connection.features.can_defer_constraint_checks and
            not connection.needs_rollback and connection.is_usable()
        )

def make_sure_mysql_usable():
    # mysql is lazily connected to in django.
    # connection.connection is None means
    # you have not connected to mysql before
    if connection.connection and not connection.is_usable():
        # destroy the default mysql connection
        # after this line, when you use ORM methods
        # django will reconnect to the default mysql
        del connections._connections.default

#
# def get_item(data_dict,item):
#     try:
#        item_value = data_dict[item]
#        return item_value
#     except:
#        return '-1'
#
# def get_config(group,config_name):
#     config = ConfigParser.ConfigParser()
#     config.readfp(open('./myapp/etc/config.ini','r'))
#     config_value=config.get(group,config_name).strip(' ').strip('\'').strip('\"')
#     return config_value
#
# def filters(data):
#     return data.strip(' ').strip('\n').strip('\br')
#
# select_limit = int(get_config('settings','select_limit'))
# export_limit = int(get_config('settings','export_limit'))
# host = get_config('settings','host')
# port = get_config('settings','port')
# user = get_config('settings','user')
# passwd = get_config('settings','passwd')
# dbname = get_config('settings','dbname')
# wrong_msg = get_config('settings','wrong_msg')
# incp_host = get_config('settings','incp_host')
# incp_port = int(get_config('settings','incp_port'))
# incp_user = get_config('settings','incp_user')
# incp_passwd = get_config('settings','incp_passwd')
# public_user = get_config('settings','public_user')

def _should_check_constraints(self, connection):
        return (
            connection.features.can_defer_constraint_checks and
            not connection.needs_rollback and connection.is_usable()
        )

def check_db_connection():
    from django.db import connection

    if connection.connection:
        #NOTE: (zacky, 2016.MAR.21st) IF CONNECTION IS CLOSED BY BACKEND, CLOSE IT AT DJANGO, WHICH WILL BE SETUP AFTERWARDS.
        if not connection.is_usable():
            connection.close()