Python Web框架
- Flask：轻量实用的Web框架
- Tornado：Facebook的开源异步Web框架
- Django：全能型Web框架
- web.py：一个小巧的Web框架
- Bottle：和Flask类似的Web框架
什么是 X-Sendfile？
X-Sendfile 是一种将文件下载请求由后端应用转交给前端 web 服务器处理的机制，它可以消除后端程序既要读文件又要处理发送的压力，从而显著提高服务器效率，特别是处理大文件下载的情形下。
X-Sendfile 通过一个特定的 HTTP header 来实现：在 X-Sendfile 头中指定一个文件的地址来通告前端 web 服务器。当 web 服务器检测到后端发送的这个 header 后，它将忽略后端的其他输出，而使用自身的组件（包括 缓存头 和 断点重连 等优化）机制将文件发送给用户。
不过，在使用 X-Sendfile 之前，我们必须明白这并不是一个标准特性，在默认情况下它是被大多数 web 服务器禁用的。而不同的 web 服务器的实现也不一样，包括规定了不同的 X-Sendfile 头格式。如果配置失当，用户可能下载到 0 字节的文件。
使用 X-Sendfile 将允许下载非 web 目录中的文件（例如/root/），即使文件在 .htaccess 保护下禁止访问，也会被下载。
Nginx 默认支持该特性，不需要加载额外的模块。只是实现有些不同，需要发送的 HTTP 头为 X-Accel-Redirect。另外，需要在配置文件中做以下设定
Nginx 默认支持该特性，不需要加载额外的模块。只是实现有些不同，需要发送的 HTTP 头为 X-Accel-Redirect。
另外，需要在配置文件中做以下设定
location /protected/ {
internal;
root /some/path;
}
internal表示这个路径只能在 Nginx 内部访问，不能用浏览器直接访问防止未授权的下载。
<?php
$filePath= '/protected/iso.img';
header('Content-type: application/octet-stream');
header('Content-Disposition: attachment; filename="'. basename($file) .'"');
//让Xsendfile发送文件
header('X-Accel-Redirect: '.$filePath);
?>
这样用户就会下载到 /some/path/protected/iso.img 这个路径下的文件。
如果你想发送的是 /some/path/iso.img 文件，那么 Nginx 配置应该是
location /protected/ {
internal;
# 注意最後的斜杠
alias /some/path/;
}
flask helpers.py
def send_file(
filename_or_fp,
mimetype=None,
as_attachment=False,
attachment_filename=None,
add_etags=True,
cache_timeout=None,
conditional=False,
last_modified=None,
):
"""Sends the contents of a file to the client. This will use the
most efficient method available and configured. By default it will
try to use the WSGI server's file_wrapper support. Alternatively
you can set the application's :attr:`~Flask.use_x_sendfile` attribute
to ``True`` to directly emit an ``X-Sendfile`` header. This however
requires support of the underlying webserver for ``X-Sendfile``.
By default it will try to guess the mimetype for you, but you can
also explicitly provide one. For extra security you probably want
to send certain files as attachment (HTML for instance). The mimetype
guessing requires a `filename` or an `attachment_filename` to be
provided.
ETags will also be attached automatically if a `filename` is provided. You
can turn this off by setting `add_etags=False`.
If `conditional=True` and `filename` is provided, this method will try to
upgrade the response stream to support range requests. This will allow
the request to be answered with partial content response.
Please never pass filenames to this function from user sources;
you should use :func:`send_from_directory` instead.
.. versionadded:: 0.2
.. versionadded:: 0.5
The `add_etags`, `cache_timeout` and `conditional` parameters were
added. The default behavior is now to attach etags.
.. versionchanged:: 0.7
mimetype guessing and etag support for file objects was
deprecated because it was unreliable. Pass a filename if you are
able to, otherwise attach an etag yourself. This functionality
will be removed in Flask 1.0
.. versionchanged:: 0.9
cache_timeout pulls its default from application config, when None.
.. versionchanged:: 0.12
The filename is no longer automatically inferred from file objects. If
you want to use automatic mimetype and etag support, pass a filepath via
`filename_or_fp` or `attachment_filename`.
.. versionchanged:: 0.12
The `attachment_filename` is preferred over `filename` for MIME-type
detection.
.. versionchanged:: 1.0
UTF-8 filenames, as specified in `RFC 2231`_, are supported.
.. _RFC 2231: https://tools.ietf.org/html/rfc2231#section-4
.. versionchanged:: 1.0.3
Filenames are encoded with ASCII instead of Latin-1 for broader
compatibility with WSGI servers.
.. versionchanged:: 1.1
Filename may be a :class:`~os.PathLike` object.
.. versionadded:: 1.1
Partial content supports :class:`~io.BytesIO`.
:param filename_or_fp: the filename of the file to send.
This is relative to the :attr:`~Flask.root_path`
if a relative path is specified.
Alternatively a file object might be provided in
which case ``X-Sendfile`` might not work and fall
back to the traditional method. Make sure that the
file pointer is positioned at the start of data to
send before calling :func:`send_file`.
:param mimetype: the mimetype of the file if provided. If a file path is
given, auto detection happens as fallback, otherwise an
error will be raised.
:param as_attachment: set to ``True`` if you want to send this file with
a ``Content-Disposition: attachment`` header.
:param attachment_filename: the filename for the attachment if it
differs from the file's filename.
:param add_etags: set to ``False`` to disable attaching of etags.
:param conditional: set to ``True`` to enable conditional responses.
:param cache_timeout: the timeout in seconds for the headers. When ``None``
(default), this value is set by
:meth:`~Flask.get_send_file_max_age` of
:data:`~flask.current_app`.
:param last_modified: set the ``Last-Modified`` header to this value,
a :class:`~datetime.datetime` or timestamp.
If a file was passed, this overrides its mtime.
"""
mtime = None
fsize = None
if hasattr(filename_or_fp, "__fspath__"):
filename_or_fp = fspath(filename_or_fp)
if isinstance(filename_or_fp, string_types):
filename = filename_or_fp
if not os.path.isabs(filename):
filename = os.path.join(current_app.root_path, filename)
file = None
if attachment_filename is None:
attachment_filename = os.path.basename(filename)
else:
file = filename_or_fp
filename = None
if mimetype is None:
if attachment_filename is not None:
mimetype = (
mimetypes.guess_type(attachment_filename)[0]
or "application/octet-stream"
)
if mimetype is None:
raise ValueError(
"Unable to infer MIME-type because no filename is available. "
"Please set either `attachment_filename`, pass a filepath to "
"`filename_or_fp` or set your own MIME-type via `mimetype`."
)
headers = Headers()
if as_attachment:
if attachment_filename is None:
raise TypeError("filename unavailable, required for sending as attachment")
if not isinstance(attachment_filename, text_type):
attachment_filename = attachment_filename.decode("utf-8")
try:
attachment_filename = attachment_filename.encode("ascii")
except UnicodeEncodeError:
filenames = {
"filename": unicodedata.normalize("NFKD", attachment_filename).encode(
"ascii", "ignore"
),
"filename*": "UTF-8''%s" % url_quote(attachment_filename, safe=b""),
}
else:
filenames = {"filename": attachment_filename}
headers.add("Content-Disposition", "attachment", **filenames)
if current_app.use_x_sendfile and filename:
if file is not None:
file.close()
headers["X-Sendfile"] = filename
fsize = os.path.getsize(filename)
headers["Content-Length"] = fsize
data = None
else:
if file is None:
file = open(filename, "rb")
mtime = os.path.getmtime(filename)
fsize = os.path.getsize(filename)
headers["Content-Length"] = fsize
elif isinstance(file, io.BytesIO):
try:
fsize = file.getbuffer().nbytes
except AttributeError:
# Python 2 doesn't have getbuffer
fsize = len(file.getvalue())
headers["Content-Length"] = fsize
data = wrap_file(request.environ, file)
rv = current_app.response_class(
data, mimetype=mimetype, headers=headers, direct_passthrough=True
)
if last_modified is not None:
rv.last_modified = last_modified
elif mtime is not None:
rv.last_modified = mtime
rv.cache_control.public = True
if cache_timeout is None:
cache_timeout = current_app.get_send_file_max_age(filename)
if cache_timeout is not None:
rv.cache_control.max_age = cache_timeout
rv.expires = int(time() + cache_timeout)
if add_etags and filename is not None:
from warnings import warn
try:
rv.set_etag(
"%s-%s-%s"
% (
os.path.getmtime(filename),
os.path.getsize(filename),
adler32(
filename.encode("utf-8")
if isinstance(filename, text_type)
else filename
)
& 0xFFFFFFFF,
)
)
except OSError:
warn(
"Access %s failed, maybe it does not exist, so ignore etags in "
"headers" % filename,
stacklevel=2,
)
if conditional:
try:
rv = rv.make_conditional(request, accept_ranges=True, complete_length=fsize)
except RequestedRangeNotSatisfiable:
if file is not None:
file.close()
raise
# make sure we don't send x-sendfile for servers that
# ignore the 304 status code for x-sendfile.
if rv.status_code == 304:
rv.headers.pop("x-sendfile", None)
return rv
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