Django文件存储 自己定制存储系统解析

要自己写一个存储系统，可以依照以下步骤：

1.写一个继承自django.core.files.storage.Storage的子类。

from django.core.files.storage import Storage
class MyStorage(Storage):
  ...

2.Django必须可以在无任何参数的情况下实例化MyStorage，所以任何环境设置必须来自django.conf.settings。

from django.conf import settings
from django.core.files.storage import Storage

class MyStorage(Storage):
  def __init__(self, option=None):
    if not option:
      option = settings.CUSTOM_STORAGE_OPTIONS
    ...

3.根据Storage的open和save方法源码:

def open(self, name, mode='rb'):
  """
  Retrieves the specified file from storage.
  """
  return self._open(name, mode)

def save(self, name, content, max_length=None):
  """
  Saves new content to the file specified by name. The content should be
  a proper File object or any python file-like object, ready to be read
  from the beginning.
  """
  # Get the proper name for the file, as it will actually be saved.
  if name is None:
    name = content.name

  if not hasattr(content, 'chunks'):
    content = File(content, name)

  name = self.get_available_name(name, max_length=max_length)
  return self._save(name, content)

MyStorage需要实现_open和_save方法。

如果写的是个本地存储系统，还要重写path方法。

4.使用django.utils.deconstruct.deconstructible装饰器，以便在migration可以序列化。

还有，Storage.delete()、Storage.exists()、Storage.listdir()、Storage.size()、Storage.url()方法都会报NotImplementedError，也需要重写。

Django Qiniu Storage

七牛云有自己的django storage系统，可以看下是怎么运作的，地址 https://github.com/glasslion/django-qiniu-storage 。

先在环境变量或者settings中配置QINIU_ACCESS_KEY、QINIU_SECRET_KEY、QINIU_BUCKET_NAME、QINIU_BUCKET_DOMAIN、QINIU_SECURE_URL。

使用七牛云托管用户上传的文件，在 settings.py 里设置DEFAULT_FILE_STORAGE：

DEFAULT_FILE_STORAGE = 'qiniustorage.backends.QiniuStorage'

使用七牛托管动态生成的文件以及站点自身的静态文件，设置：

STATICFILES_STORAGE = 'qiniustorage.backends.QiniuStaticStorage'

运行python manage.py collectstatic，静态文件就会被统一上传到七牛。

QiniuStorage代码如下：

@deconstructible
class QiniuStorage(Storage):
  """
  Qiniu Storage Service
  """
  location = ""

  def __init__(
      self,
      access_key=QINIU_ACCESS_KEY,
      secret_key=QINIU_SECRET_KEY,
      bucket_name=QINIU_BUCKET_NAME,
      bucket_domain=QINIU_BUCKET_DOMAIN,
      secure_url=QINIU_SECURE_URL):

    self.auth = Auth(access_key, secret_key)
    self.bucket_name = bucket_name
    self.bucket_domain = bucket_domain
    self.bucket_manager = BucketManager(self.auth)
    self.secure_url = secure_url

  def _clean_name(self, name):
    """
    Cleans the name so that Windows style paths work
    """
    # Normalize Windows style paths
    clean_name = posixpath.normpath(name).replace('\\', '/')

    # os.path.normpath() can strip trailing slashes so we implement
    # a workaround here.
    if name.endswith('/') and not clean_name.endswith('/'):
      # Add a trailing slash as it was stripped.
      return clean_name + '/'
    else:
      return clean_name

  def _normalize_name(self, name):
    """
    Normalizes the name so that paths like /path/to/ignored/../foo.txt
    work. We check to make sure that the path pointed to is not outside
    the directory specified by the LOCATION setting.
    """

    base_path = force_text(self.location)
    base_path = base_path.rstrip('/')

    final_path = urljoin(base_path.rstrip('/') + "/", name)

    base_path_len = len(base_path)
    if (not final_path.startswith(base_path) or
        final_path[base_path_len:base_path_len + 1] not in ('', '/')):
      raise SuspiciousOperation("Attempted access to '%s' denied." %
                   name)
    return final_path.lstrip('/')

  def _open(self, name, mode='rb'):
    return QiniuFile(name, self, mode)

  def _save(self, name, content):
    cleaned_name = self._clean_name(name)
    name = self._normalize_name(cleaned_name)

    if hasattr(content, 'chunks'):
      content_str = b''.join(chunk for chunk in content.chunks())
    else:
      content_str = content.read()

    self._put_file(name, content_str)
    return cleaned_name

  def _put_file(self, name, content):
    token = self.auth.upload_token(self.bucket_name)
    ret, info = put_data(token, name, content)
    if ret is None or ret['key'] != name:
      raise QiniuError(info)

  def _read(self, name):
    return requests.get(self.url(name)).content

  def delete(self, name):
    name = self._normalize_name(self._clean_name(name))
    if six.PY2:
      name = name.encode('utf-8')
    ret, info = self.bucket_manager.delete(self.bucket_name, name)

    if ret is None or info.status_code == 612:
      raise QiniuError(info)

  def _file_stat(self, name, silent=False):
    name = self._normalize_name(self._clean_name(name))
    if six.PY2:
      name = name.encode('utf-8')
    ret, info = self.bucket_manager.stat(self.bucket_name, name)
    if ret is None and not silent:
      raise QiniuError(info)
    return ret

  def exists(self, name):
    stats = self._file_stat(name, silent=True)
    return True if stats else False

  def size(self, name):
    stats = self._file_stat(name)
    return stats['fsize']

  def modified_time(self, name):
    stats = self._file_stat(name)
    time_stamp = float(stats['putTime']) / 10000000
    return datetime.datetime.fromtimestamp(time_stamp)

  def listdir(self, name):
    name = self._normalize_name(self._clean_name(name))
    if name and not name.endswith('/'):
      name += '/'

    dirlist = bucket_lister(self.bucket_manager, self.bucket_name,
                prefix=name)
    files = []
    dirs = set()
    base_parts = name.split("/")[:-1]
    for item in dirlist:
      parts = item['key'].split("/")
      parts = parts[len(base_parts):]
      if len(parts) == 1:
        # File
        files.append(parts[0])
      elif len(parts) > 1:
        # Directory
        dirs.add(parts[0])
    return list(dirs), files

  def url(self, name):
    name = self._normalize_name(self._clean_name(name))
    name = filepath_to_uri(name)
    protocol = u'https://' if self.secure_url else u'http://'
    return urljoin(protocol + self.bucket_domain, name)

配置是从环境变量或者settings.py中获得的：

def get_qiniu_config(name, default=None):
  """
  Get configuration variable from environment variable
  or django setting.py
  """
  config = os.environ.get(name, getattr(settings, name, default))
  if config is not None:
    if isinstance(config, six.string_types):
      return config.strip()
    else:
      return config
  else:
    raise ImproperlyConfigured(
      "Can't find config for '%s' either in environment"
      "variable or in setting.py" % name)
QINIU_ACCESS_KEY = get_qiniu_config('QINIU_ACCESS_KEY')
QINIU_SECRET_KEY = get_qiniu_config('QINIU_SECRET_KEY')
QINIU_BUCKET_NAME = get_qiniu_config('QINIU_BUCKET_NAME')
QINIU_BUCKET_DOMAIN = get_qiniu_config('QINIU_BUCKET_DOMAIN', '').rstrip('/')
QINIU_SECURE_URL = get_qiniu_config('QINIU_SECURE_URL', 'False')

重写了_open和_save方法：

def _open(self, name, mode='rb'):
  return QiniuFile(name, self, mode)
def _save(self, name, content):
  cleaned_name = self._clean_name(name)
  name = self._normalize_name(cleaned_name)
  if hasattr(content, 'chunks'):
    content_str = b''.join(chunk for chunk in content.chunks())
  else:
    content_str = content.read()
  self._put_file(name, content_str)
  return cleaned_name

使用的put_data方法上传文件，相关代码如下：

def put_data(
    up_token, key, data, params=None, mime_type='application/octet-stream', check_crc=False, progress_handler=None,
    fname=None):
  """上传二进制流到七牛
  Args:
    up_token:     上传凭证
    key:       上传文件名
    data:       上传二进制流
    params:      自定义变量，规格参考 http://developer.qiniu.com/docs/v6/api/overview/up/response/vars.html#xvar
    mime_type:    上传数据的mimeType
    check_crc:    是否校验crc32
    progress_handler: 上传进度

  Returns:
    一个dict变量，类似 {"hash": "<Hash string>", "key": "<Key string>"}
    一个ResponseInfo对象
  """
  crc = crc32(data) if check_crc else None
  return _form_put(up_token, key, data, params, mime_type, crc, progress_handler, fname)

def _form_put(up_token, key, data, params, mime_type, crc, progress_handler=None, file_name=None):
  fields = {}
  if params:
    for k, v in params.items():
      fields[k] = str(v)
  if crc:
    fields['crc32'] = crc
  if key is not None:
    fields['key'] = key
  fields['token'] = up_token
  url = config.get_default('default_zone').get_up_host_by_token(up_token) + '/'
  # name = key if key else file_name

  fname = file_name
  if not fname or not fname.strip():
    fname = 'file_name'

  r, info = http._post_file(url, data=fields, files={'file': (fname, data, mime_type)})
  if r is None and info.need_retry():
    if info.connect_failed:
      url = config.get_default('default_zone').get_up_host_backup_by_token(up_token) + '/'
    if hasattr(data, 'read') is False:
      pass
    elif hasattr(data, 'seek') and (not hasattr(data, 'seekable') or data.seekable()):
      data.seek(0)
    else:
      return r, info
    r, info = http._post_file(url, data=fields, files={'file': (fname, data, mime_type)})

  return r, info
def _post_file(url, data, files):
  return _post(url, data, files, None)
def _post(url, data, files, auth, headers=None):
  if _session is None:
    _init()
  try:
    post_headers = _headers.copy()
    if headers is not None:
      for k, v in headers.items():
        post_headers.update({k: v})
    r = _session.post(
      url, data=data, files=files, auth=auth, headers=post_headers,
      timeout=config.get_default('connection_timeout'))
  except Exception as e:
    return None, ResponseInfo(None, e)
  return __return_wrapper(r)
def _init():
  session = requests.Session()
  adapter = requests.adapters.HTTPAdapter(
    pool_connections=config.get_default('connection_pool'), pool_maxsize=config.get_default('connection_pool'),
    max_retries=config.get_default('connection_retries'))
  session.mount('http://', adapter)
  global _session
  _session = session

最终使用的是requests库上传文件的，统一适配了链接池个数、链接重试次数。

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