1. # 这里引入了redis模块，这个是redis-python库的接口，用于通过python访问redis数据库，
    2. # 这个文件主要是实现连接redis数据库的功能，这些连接接口在其他文件中经常被用到
    4. import redis
    5. import six
    7. from scrapy.utils.misc import load_object
    9. DEFAULT_REDIS_CLS = redis.StrictRedis
    11. # 可以在settings文件中配置套接字的超时时间、等待时间等
    12. # Sane connection defaults.
    13. DEFAULT_PARAMS = {
    14.     'socket_timeout': 30,
    15.     'socket_connect_timeout': 30,
    16.     'retry_on_timeout': True,
    17. }
    19. # 要想连接到redis数据库，和其他数据库差不多，
    20. # 需要一个ip地址、端口号、用户名密码（可选）和一个整形的数据库编号
    21. # Shortcut maps 'setting name' -> 'parmater name'.
    22. SETTINGS_PARAMS_MAP = {
    23.     'REDIS_URL': 'url',
    24.     'REDIS_HOST': 'host',
    25.     'REDIS_PORT': 'port',
    26. }
    29. def get_redis_from_settings(settings):
    30.     """Returns a redis client instance from given Scrapy settings object.
    31.     This function uses ``get_client`` to instantiate the client and uses
    32.     ``DEFAULT_PARAMS`` global as defaults values for the parameters. You can
    33.     override them using the ``REDIS_PARAMS`` setting.
    34.     Parameters
    35.     ----------
    36.     settings : Settings
    37.         A scrapy settings object. See the supported settings below.
    38.     Returns
    39.     -------
    40.     server
    41.         Redis client instance.
    42.     Other Parameters
    43.     ----------------
    44.     REDIS_URL : str, optional
    45.         Server connection URL.
    46.     REDIS_HOST : str, optional
    47.         Server host.
    48.     REDIS_PORT : str, optional
    49.         Server port.
    50.     REDIS_PARAMS : dict, optional
    51.         Additional client parameters.
    52.     """
    53.     params = DEFAULT_PARAMS.copy()
    54.     params.update(settings.getdict('REDIS_PARAMS'))
    55.     # XXX: Deprecate REDIS_* settings.
    56.     for source, dest in SETTINGS_PARAMS_MAP.items():
    57.         val = settings.get(source)
    58.         if val:
    59.             params[dest] = val
    61.     # Allow ``redis_cls`` to be a path to a class.
    62.     if isinstance(params.get('redis_cls'), six.string_types):
    63.         params['redis_cls'] = load_object(params['redis_cls'])
    65.     # 返回的是redis库的Redis对象，可以直接用来进行数据操作的对象
    66.     return get_redis(**params)
    69. # Backwards compatible alias.
    70. from_settings = get_redis_from_settings
    73. def get_redis(**kwargs):
    74.     """Returns a redis client instance.
    75.     Parameters
    76.     ----------
    77.     redis_cls : class, optional
    78.         Defaults to ``redis.StrictRedis``.
    79.     url : str, optional
    80.         If given, ``redis_cls.from_url`` is used to instantiate the class.
    81.     **kwargs
    82.         Extra parameters to be passed to the ``redis_cls`` class.
    83.     Returns
    84.     -------
    85.     server
    86.         Redis client instance.
    87.     """
    88.     redis_cls = kwargs.pop('redis_cls', DEFAULT_REDIS_CLS)
    89.     url = kwargs.pop('url', None)
    92.     if url:
    93.         return redis_cls.from_url(url, **kwargs)
    94.     else:
    95.         return redis_cls(**kwargs)
    97. connection.py