Django 大文件下載實(shí)現(xiàn)過(guò)程解析

更新時(shí)間：2019年08月01日 10:07:53 作者：再見(jiàn)紫羅蘭

這篇文章主要介紹了Django 大文件下載實(shí)現(xiàn)過(guò)程解析,文中通過(guò)示例代碼介紹的非常詳細(xì)，對(duì)大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價(jià)值,需要的朋友可以參考下

django提供文件下載時(shí)，若果文件較小，解決辦法是先將要傳送的內(nèi)容全生成在內(nèi)存中，然后再一次性傳入Response對(duì)象中：

def simple_file_download(request):
  # do something...
  content = open("simplefile", "rb").read()

如果文件非常大時(shí)，最簡(jiǎn)單的辦法就是使用靜態(tài)文件服務(wù)器，比如Apache或者Nginx服務(wù)器來(lái)處理下載。不過(guò)有時(shí)候，我們需要對(duì)用戶(hù)的權(quán)限做一下限定，或者不想向用戶(hù)暴露文件的真實(shí)地址，或者這個(gè)大內(nèi)容是臨時(shí)生成的(比如臨時(shí)將多個(gè)文件合并而成的)，這時(shí)就不能使用靜態(tài)文件服務(wù)器了。

django文檔中提到，可以向HttpResponse傳遞一個(gè)迭代器，流式的向客戶(hù)端傳遞數(shù)據(jù)。

要自己寫(xiě)迭代器的話(huà)，可以用yield：

def read_file(filename, buf_size=8192):
  with open(filename, "rb") as f:
    while True:
      content = f.read(buf_size)
      if content:
        yield content
      else:
        break
def big_file_download(request):
  filename = "filename"
  response = HttpResponse(read_file(filename))
  return response

或者使用生成器表達(dá)式，下面是django文檔中提供csv大文件下載的例子：

import csv
 
from django.utils.six.moves import range
from django.http import StreamingHttpResponse
 
class Echo(object):
  """An object that implements just the write method of the file-like
  interface.
  """
  def write(self, value):
    """Write the value by returning it, instead of storing in a buffer."""
    return value
 
def some_streaming_csv_view(request):
  """A view that streams a large CSV file."""
  # Generate a sequence of rows. The range is based on the maximum number of
  # rows that can be handled by a single sheet in most spreadsheet
  # applications.
  rows = (["Row {0}".format(idx), str(idx)] for idx in range(65536))
  pseudo_buffer = Echo()
  writer = csv.writer(pseudo_buffer)
  response = StreamingHttpResponse((writer.writerow(row) for row in rows),
                   content_type="text/csv")
  response['Content-Disposition'] = 'attachment; filename="somefilename.csv"'
  return response

python也提供一個(gè)文件包裝器，將類(lèi)文件對(duì)象包裝成一個(gè)迭代器：

class FileWrapper:
  """Wrapper to convert file-like objects to iterables""" 
  def __init__(self, filelike, blksize=8192):
    self.filelike = filelike
    self.blksize = blksize
    if hasattr(filelike,'close'):
      self.close = filelike.close 
  def __getitem__(self,key):
    data = self.filelike.read(self.blksize)
    if data:
      return data
    raise IndexError 
  def __iter__(self):
    return self 
  def next(self):
    data = self.filelike.read(self.blksize)
    if data:
      return data
    raise StopIteration

使用時(shí)：

from django.core.servers.basehttp import FileWrapper
from django.http import HttpResponse
import os
def file_download(request,filename):
 
  wrapper = FileWrapper(open(filename, 'rb'))
  response = HttpResponse(wrapper, content_type='application/octet-stream')
  response['Content-Length'] = os.path.getsize(path)
  response['Content-Disposition'] = 'attachment; filename=%s' % filename
  return response

django也提供了StreamingHttpResponse類(lèi)來(lái)代替HttpResponse對(duì)流數(shù)據(jù)進(jìn)行處理。

壓縮為zip文件下載：

import os, tempfile, zipfile 
from django.http import HttpResponse 
from django.core.servers.basehttp import FileWrapper 
def send_zipfile(request): 
  """                                     
  Create a ZIP file on disk and transmit it in chunks of 8KB,         
  without loading the whole file into memory. A similar approach can     
  be used for large dynamic PDF files.                    
  """ 
  temp = tempfile.TemporaryFile() 
  archive = zipfile.ZipFile(temp, 'w', zipfile.ZIP_DEFLATED) 
  for index in range(10): 
    filename = __file__ # Select your files here.              
    archive.write(filename, 'file%d.txt' % index) 
  archive.close() 
  wrapper = FileWrapper(temp) 
  response = HttpResponse(wrapper, content_type='application/zip') 
  response['Content-Disposition'] = 'attachment; filename=test.zip' 
  response['Content-Length'] = temp.tell() 
  temp.seek(0) 
  return response

不過(guò)不管怎么樣，使用django來(lái)處理大文件下載都不是一個(gè)很好的注意，最好的辦法是django做權(quán)限判斷，然后讓靜態(tài)服務(wù)器處理下載。

這需要使用sendfile的機(jī)制："傳統(tǒng)的Web服務(wù)器在處理文件下載的時(shí)候，總是先讀入文件內(nèi)容到應(yīng)用程序內(nèi)存，然后再把內(nèi)存當(dāng)中的內(nèi)容發(fā)送給客戶(hù)端瀏覽器。這種方式在應(yīng)付當(dāng)今大負(fù)載網(wǎng)站會(huì)消耗更多的服務(wù)器資源。sendfile是現(xiàn)代操作系統(tǒng)支持的一種高性能網(wǎng)絡(luò)IO方式，操作系統(tǒng)內(nèi)核的sendfile調(diào)用可以將文件內(nèi)容直接推送到網(wǎng)卡的buffer當(dāng)中，從而避免了Web服務(wù)器讀寫(xiě)文件的開(kāi)銷(xiāo)，實(shí)現(xiàn)了“零拷貝”模式。 "

Apache服務(wù)器里需要mod_xsendfile模塊來(lái)實(shí)現(xiàn)，而Nginx是通過(guò)稱(chēng)為X-Accel-Redirect的特性來(lái)實(shí)現(xiàn)。

nginx配置文件：

# Will serve /var/www/files/myfile.tar.gz
# When passed URI /protected_files/myfile.tar.gz
location /protected_files {
  internal;
  alias /var/www/files;
}

或者

# Will serve /var/www/protected_files/myfile.tar.gz
# When passed URI /protected_files/myfile.tar.gz
location /protected_files {
  internal;
  root /var/www;
}

注意alias和root的區(qū)別。

django中：

response['X-Accel-Redirect']='/protected_files/%s'%filename

這樣當(dāng)向django view函數(shù)發(fā)起request時(shí)，django負(fù)責(zé)對(duì)用戶(hù)權(quán)限進(jìn)行判斷或者做些其它事情，然后向nginx轉(zhuǎn)發(fā)url為/protected_files/filename的請(qǐng)求，nginx服務(wù)器負(fù)責(zé)文件/var/www/protected_files/filename的下載：

@login_required
def document_view(request, document_id):
  book = Book.objects.get(id=document_id)
  response = HttpResponse()
  name=book.myBook.name.split('/')[-1]
  response['Content_Type']='application/octet-stream'
  response["Content-Disposition"] = "attachment; filename={0}".format(
      name.encode('utf-8'))
  response['Content-Length'] = os.path.getsize(book.myBook.path)
  response['X-Accel-Redirect'] = "/protected/{0}".format(book.myBook.name)
  return response

以上就是本文的全部?jī)?nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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