Nginx¶
If you serve Django behind Nginx, then you can delegate the file streaming to Nginx and get increased performance:
- lower resources used by Python/Django workers ;
- faster download.
See Nginx X-accel documentation [1] for details.
Known limitations¶
- Nginx needs access to the resource by URL (proxy) or path (location).
- Thus
VirtualFile
and any generated files cannot be streamed by Nginx.
Given a view¶
Let’s consider the following view:
import os
from django.conf import settings
from django.core.files.storage import FileSystemStorage
from django_downloadview import StorageDownloadView
storage_dir = os.path.join(settings.MEDIA_ROOT, 'nginx')
storage = FileSystemStorage(location=storage_dir,
base_url=''.join([settings.MEDIA_URL, 'nginx/']))
optimized_by_middleware = StorageDownloadView.as_view(storage=storage,
path='hello-world.txt')
What is important here is that the files will have an url
property
implemented by storage. Let’s setup an optimization rule based on that URL.
Note
It is generally easier to setup rules based on URL rather than based on name in filesystem. This is because path is generally relative to storage, whereas URL usually contains some storage identifier, i.e. it is easier to target a specific location by URL rather than by filesystem name.
Setup XAccelRedirect middlewares¶
Make sure django_downloadview.SmartDownloadMiddleware
is in
MIDDLEWARE_CLASSES
of your Django settings.
Example:
'django.middleware.common.CommonMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django_downloadview.SmartDownloadMiddleware'
]
# END middlewares
Then set django_downloadview.nginx.XAccelRedirectMiddleware
as
DOWNLOADVIEW_BACKEND
:
# BEGIN backend
Then register as many DOWNLOADVIEW_RULES
as you wish:
DOWNLOADVIEW_BACKEND = 'django_downloadview.lighttpd.XSendfileMiddleware'
"""
# BEGIN rules
DOWNLOADVIEW_RULES = [
'destination_dir': '/lighttpd-optimized-by-middleware/',
Each item in DOWNLOADVIEW_RULES
is a dictionary of keyword arguments passed
to the middleware factory. In the example above, we capture responses by
source_url
and convert them to internal redirects to destination_url
.
-
class
django_downloadview.nginx.middlewares.
XAccelRedirectMiddleware
(source_dir=None, source_url=None, destination_url=None, expires=None, with_buffering=None, limit_rate=None, media_root=None, media_url=None)¶ Bases:
django_downloadview.middlewares.ProxiedDownloadMiddleware
Configurable middleware, for use in decorators or in global middlewares.
Standard Django middlewares are configured globally via settings. Instances of this class are to be configured individually. It makes it possible to use this class as the factory in
django_downloadview.decorators.DownloadDecorator
.-
get_redirect_url
(response)¶ Return redirect URL for file wrapped into response.
-
is_download_response
(response)¶ Return True for DownloadResponse, except for “virtual” files.
This implementation cannot handle files that live in memory or which are to be dynamically iterated over. So, we capture only responses whose file attribute have either an URL or a file name.
-
process_response
(request, response)¶ Call process_download_response() if
response
is download.
-
process_download_response
(request, response)¶ Replace DownloadResponse instances by NginxDownloadResponse ones.
-
Per-view setup with x_accel_redirect decorator¶
Middlewares should be enough for most use cases, but you may want per-view
configuration. For nginx, there is x_accel_redirect
:
-
django_downloadview.nginx.decorators.
x_accel_redirect
(view_func, *args, **kwargs)¶ Apply
XAccelRedirectMiddleware
toview_func
.Proxies (
*args
,**kwargs
) to middleware constructor.
As an example:
import os
from django.conf import settings
from django.core.files.storage import FileSystemStorage
from django_downloadview import StorageDownloadView
from django_downloadview.nginx import x_accel_redirect
optimized_by_decorator = x_accel_redirect(
StorageDownloadView.as_view(storage=storage, path='hello-world.txt'),
source_url=storage.base_url,
destination_url='/nginx-optimized-by-decorator/')
Test responses with assert_x_accel_redirect¶
Use assert_x_accel_redirect()
function as a shortcut in your tests.
import os
from django.core.files.base import ContentFile
from django.core.urlresolvers import reverse
import django.test
from django_downloadview.nginx import assert_x_accel_redirect
from demoproject.nginx.views import storage, storage_dir
def setup_file():
if not os.path.exists(storage_dir):
os.makedirs(storage_dir)
storage.save('hello-world.txt', ContentFile(u'Hello world!\n'))
class OptimizedByMiddlewareTestCase(django.test.TestCase):
def test_response(self):
"""'nginx:optimized_by_middleware' returns X-Accel response."""
setup_file()
url = reverse('nginx:optimized_by_middleware')
response = self.client.get(url)
assert_x_accel_redirect(
self,
response,
content_type="text/plain; charset=utf-8",
charset="utf-8",
basename="hello-world.txt",
redirect_url="/nginx-optimized-by-middleware/hello-world.txt",
expires=None,
with_buffering=None,
limit_rate=None)
class OptimizedByDecoratorTestCase(django.test.TestCase):
def test_response(self):
"""'nginx:optimized_by_decorator' returns X-Accel response."""
setup_file()
url = reverse('nginx:optimized_by_decorator')
response = self.client.get(url)
assert_x_accel_redirect(
self,
response,
content_type="text/plain; charset=utf-8",
charset="utf-8",
basename="hello-world.txt",
redirect_url="/nginx-optimized-by-decorator/hello-world.txt",
expires=None,
with_buffering=None,
limit_rate=None)
-
django_downloadview.nginx.tests.
assert_x_accel_redirect
(test_case, response, **assertions)¶ Make
test_case
assert thatresponse
is a XAccelRedirectResponse.Optional
assertions
dictionary can be used to check additional items:basename
: the basename of the file in the response.content_type
: the value of “Content-Type” header.redirect_url
: the value of “X-Accel-Redirect” header.charset
: the value ofX-Accel-Charset
header.with_buffering
: the value ofX-Accel-Buffering
header. IfFalse
, then makes sure that the header disables buffering. IfNone
, then makes sure that the header is not set.expires
: the value ofX-Accel-Expires
header. IfFalse
, then makes sure that the header disables expiration. IfNone
, then makes sure that the header is not set.limit_rate
: the value ofX-Accel-Limit-Rate
header. IfFalse
, then makes sure that the header disables limit rate. IfNone
, then makes sure that the header is not set.
The tests above assert the Django part is OK. Now let’s configure nginx.
Setup Nginx¶
See Nginx X-accel documentation [1] for details.
Here is what you could have in /etc/nginx/sites-available/default
:
charset utf-8;
# Django-powered service.
upstream frontend {
server 127.0.0.1:8000 fail_timeout=0;
}
server {
listen 80 default;
# File-download proxy.
#
# Will serve /var/www/files/myfile.tar.gz when passed URI
# like /optimized-download/myfile.tar.gz
#
# See http://wiki.nginx.org/X-accel
# and https://django-downloadview.readthedocs.org
#
location /proxied-download {
internal;
# Location to files on disk.
alias /var/www/files/;
}
# Proxy to Django-powered frontend.
location / {
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
proxy_redirect off;
proxy_pass http://frontend;
}
}
... where specific configuration is the location /optimized-download
section.
Note
/proxied-download
has the internal
flag, so this location is not
available for the client, i.e. users are not able to download files via
/optimized-download/<filename>
.
Assert everything goes fine with healthchecks¶
Healthchecks are the best way to check the complete setup.
Common issues¶
Unknown charset "utf-8" to override
¶
Add charset utf-8;
in your nginx configuration file.
open() "path/to/something" failed (2: No such file or directory)
¶
Check your settings.NGINX_DOWNLOAD_MIDDLEWARE_MEDIA_ROOT
in Django
configuration VS alias
in nginx configuration: in a standard configuration,
they should be equal.
References
[1] | (1, 2) http://wiki.nginx.org/X-accel |