During the processing of a request in Django, I need to perform a nested request to the same application. Consider this example, where while processing the sendmail request, I attempt to make another request to the same server to obtain the content of an attachment (the body of the mail and a list of urls whose content to attach are provided to the sendmail view function through POST parameters):
def sendmail(request):
mail = #... create a mail object
for url in urls: # iterate over desired attachments urls
data = urllib.urlopen('http://127.0.0.1:8000' + url).read()
mail.attach(data)
There are several issues with this approach. First, it doesn't work with the development server because it can only process one request at a time: as it is already processing the sendmail request, attempting to read from the given url will block forever.
Second, I have to specify the server's ip and port, which is not very nice.
I would like to do something like that instead:
data = django_get(url).read()
where the hypothetical django_get method would not really make an http request, but instead directly call the django component that takes an url and returns an HttpResponse. That would solve both problems, as there would not be any actual socket connection, and it would not be necessary to include the server/port in the url. How could that be achieved?
The opposite of reverse() is resolve().
Also, this.
This is Ignacio Vazquez-Abrams' answer for the lazy:
from django.core.urlresolvers import resolve
def sendmail(request):
mail = #... create a mail object
for url in urls: # iterate over desired attachments urls
resolved = resolve(url)
request.path = url
mail.attach(resolved.func(request, *resolved.args, **resolved.kwargs))
Put the desired functionality in a separate function that both your sendmail function and the original page's function can call.
Related
Background
I have a service A accessible with HTTP requests. And I have other services that want to invoke these APIs.
Problem
When I test service A's APIs with POSTMAN, every request works fine. But when I user python's requests library to make these request, there is one PUT method that just won't work. For some reason, the PUT method being called cannot receive the data (HTTP body) at all, though it can receive headers. On the other side, the POST method called in the same manner receives the data perfectly.
I managed to achieve my goal simply by using httplib library instead, but I am still quite baffled by what exactly happened here.
The Crime Scene
Route 1:
#app.route("/private/serviceA", methods = ['POST'])
#app.route("/private/serviceA/", methods = ['POST'])
def A_create():
# request.data contains correct data that can be read with request.get_json()
Route 2:
#app.route("/private/serviceA/<id>", methods = ['PUT'])
#app.route("/private/serviceA/<id>/", methods = ['PUT'])
def A_update(id):
# request.data is empty, though request.headers contains headers I passed in
# This happens when sending the request with Python requests library, but not when sending with httplib library or with POSTMAN
# Also, data comes in fine when all other routes are commented out
# Unless all other routes are commented out, this happens even when the function body has only one line printing request.data
Route 3:
#app.route("/private/serviceA/schema", methods = ['PUT'])
def schema_update_column():
# This one again works perfectly fine
Using POSTMAN:
Using requests library from another service:
#app.route("/public/serviceA/<id>", methods = ['PUT'])
def A_update(id):
content = request.get_json()
headers = {'content-type': 'application/json'}
response = requests.put('%s:%s' % (router_config.HOST, serviceA_instance_id) + '/private/serviceA/' + str(id), data=json.dumps(content), headers = headers)
return Response(response.content, mimetype='application/json', status=response.status_code)
Using httplib library from another service:
#app.route('/public/serviceA/<id>', methods=['PUT'])
def update_course(id):
content= request.get_json()
headers = {'content-type': 'application/json'}
conn = httplib.HTTPConnection('%s:%s' % (router_config.HOST, serviceA_instance_id))
conn.request("PUT", "/private/serviceA/%s/" % id, json.dumps(content), headers)
return str(conn.getresponse().read())
Questions
1. What am I doing wrong for the route 2?
2. For route 2, the handler doesn't seem to be executed when either handler is commented out, which also confuses me. Is there something important about Flask that I'm not aware of?
Code Repo
Just in case some nice ppl are interested enough to look at the messy undocumented code...
https://github.com/fantastic4ever/project1
The serviceA corresponds to course service (course_flask.py), and the service calling it corresponds to router service (router.py).
The version that was still using requests library is 747e69a11ed746c9e8400a8c1e86048322f4ec39.
In your use of the requests library, you are using requests.post, which is sending a POST request. If you use requests.put then you would send a PUT request. That could be the issue.
Request documentation
I am trying to create an admin command that will simulate some api calls associated with a view but I don't want to hard code the url, for example like that url='http://127.0.0.1:8000/api/viewname', in order to send the request.
If I use the reverse option I can obtain half the url /api/viewname.
If I try to post the request that way
url = reverse('name-of-view')
requests.post(url, data=some_data)
I get
requests.exceptions.MissingSchema: Invalid URL '/api/viewname/': No schema supplied. Perhaps you meant http:///api/viewname/?
Do I have to look whether the server is running on the localhost or is there a more generic way?
requests module needs the absolute url to post to. you need
url = 'http://%s%s' % (request.META['HTTP_HOST'], reverse('name-of-view'))
requests.post(url, data=some_data)
I am developing a ExtJS application that uses a Django-rest-framework service. I am using CORS headers to allow fetching the data from the service (https://github.com/OttoYiu/django-cors-headers).
What happens is that at a point in time I want to change the URL from the store. And when I do that I get the following error:
XMLHttpRequest cannot load http://10.98.0.241:8000/reacsearch/as?_dc=1418831884352&page=1&start=0&limit=25. The request was redirected to 'http://10.98.0.241:8000/reacsearch/as/?_dc=1418831884352&page=1&start=0&limit=25', which is disallowed for cross-origin requests that require preflight.
In the settings.oy I define the following properties for the CORS
CORS_ALLOW_METHODS = (
'GET',
'OPTIONS'
)
CORS_ORIGIN_ALLOW_ALL = True
This works fine when I use URLs to list all the elements in my database, however when I change the store for another URL I get the error above. Also the link works fine in the browser.
The store url change is made this way:
var store = Ext.getStore(storeName);
store.getProxy().setUrl(newURL);
store.load();
The difference between the views, is that the two that work on the application are viewsets, while the other is just a generic list
class Example1viewset(viewsets.ModelViewSet):
"""
API endpoing that allows metabolites to be viewed.
"""
queryset = examples1.objects.all()
serializer_class = Example1Serializer
class Example1SearchList(generics.ListAPIView):
serializer_class = Example1Serializer
def get_queryset(self):
queryset = Example.objects.all()
if 'attr' in self.kwargs:
queryset = queryset.filter(Q(attribute1__contains=self.kwargs['attr']) | Q(attribute2__contains=self.kwargs['abbr']))
return queryset
Like I mentioned both examples work fine in the browser (even accessing through other computers in the network), however in the application when changing the URL of the store I get the CORS error. Does anyone has any idea why this is happening?
Thank you.
Edit:
Just for clarification, the problem is not in changing the url of the store. As I tried to set those urls as defaults, but they are not working when accessing from the application.
My urls.py file:
router = routers.DefaultRouter()
router.register(r'example', views.Example1ViewSet)
# Wire up our API using automatic URL routing.
# Additionally, we include login URLs for the browsable API.
urlpatterns = [
url(r'^', include(router.urls)),
url(r'^reacsearch/(?P<attr>.+)/$', Example1SearchList.as_view()),
url(r'^api-auth/', include('rest_framework.urls', namespace='rest_framework'))
Can it be that the problem is related with the fact that I am not adding the search list to the router?
Edit2
Problem solved since I was trying to fetch data from a different domain. I changed the type of store to jsonp in Extjs, and I also allowed my rest service to render data as jsonp.
Just a reminder if anyone comes accross this same problem, it is necessary to add ?format=jsonp to the store url:
http://my/url/?format=jsonp
Since it looks like an alternate solution was found, I'll explain what the issue appeared to be as well as why the alternative works.
XMLHttpRequest cannot load first url. The request was redirected to 'second url', which is disallowed for cross-origin requests that require preflight.
The issue here is that you are telling Django to enforce the trailing slash, which makes it automatically redirect urls without a trailing slash to urls with a trailing slash, assuming that one exists. This is why, as stated in the error, the request was redirected to the second url, which you can tell has the missing trailing slash. This is controlled by the APPEND_SLASH Django setting which is True by default.
The problem is that when CORS is doing a preflight request, which is what allows it to determine if the request can be made, there must be a valid response at the requested URL. Because you are redirecting the request, the preflight request fails and you're stuck without your information.
You can fix this by adding the trailing slash in your code. There appear to be a few solutions for doing this with ext, but I personally can't recommend a specific one. You can also manually set the url to use the trailing slash, which sounds like what you were doing previously.
Or you can use JSONP...
You've found the alternative solution, which is to use JSONP to make the request instead of relying on CORS. This gets around the preflight issue and works in all major browsers, but there are some drawbacks to consider. You can find more information on CORS vs JSONP by looking around.
You're going to need CORS if you want to push any changes to your API, as JSONP only supports GET requests. There are other advantages, such as the ability to abort requests, that also comes with CORS.
I'm working on a Django web application which (amongst other things) needs to handle transaction status info sent using a POST request.
In addition to the HTTP security supported by the payment gateway, my view checks request.META['HTTP_REFERER'] against an entry in settings.py to try to prevent funny business:
if request.META.get('HTTP_REFERER', '') != settings.PAYMENT_URL and not settings.DEBUG:
return HttpResponseForbidden('Incorrect source URL for updating payment status')
Now I'd like to work out how to test this behaviour.
I can generate a failure easily enough; HTTP_REFERER is (predictably) None with a normal page load:
def test_transaction_status_succeeds(self):
response = self.client.post(reverse('transaction_status'), { ... })
self.assertEqual(response.status_code, 403)
How, though, can I fake a successful submission? I've tried setting HTTP_REFERER in extra, e.g. self.client.post(..., extra={'HTTP_REFERER': 'http://foo/bar'}), but this isn't working; the view is apparently still seeing a blank header.
Does the test client even support custom headers? Is there a work-around if not? I'm using Django 1.1, and would prefer not to upgrade just yet if at all possible.
Almost right. It's actually:
def transaction_status_suceeds(self):
response = self.client.post(reverse('transaction_status'), {}, HTTP_REFERER='http://foo/bar')
I'd missed a ** (scatter operator / keyword argument unpacking operator / whatever) when reading the source of test/client.py; extra ends up being a dictionary of extra keyword arguments to the function itself.
You can pass HTTP headers to the constructor of Client:
from django.test import Client
from django.urls import reverse
client = Client(
HTTP_USER_AGENT='Mozilla/5.0',
HTTP_REFERER='http://www.google.com',
)
response1 = client.get(reverse('foo'))
response2 = client.get(reverse('bar'))
This way you don't need to pass headers every time you make a request.
I am reading a djangobook and get questions about HttpResponseRedirect and render_to_response.
suppose I have a contact form, which posts data to confirm view. It goes through all the validation and database stuff. Then, as a usual way, I output the html with
return render_to_response('thank_you.html',
dict(user_code = user_code),
context_instance=RequestContext(request))
However, the book suggested "You should always issue a redirect for successful POST requests." because if the user "Refresh" on a this page, the request will be repeated. I wonder what's the best way to send the user_code along through HttpResponseRedirect to the thank_you.html.
Pass the information in a query string:
thank_you/?user_code=1234
Or use a session variable.
The problem with a query string is that the user can see the data.
When you send a redirect, you are sending the user back a response (a 302 HTTP response) and they are then making an entirely new request to the provided URL. That's a completely new request/response cycle so there is no way to supply data unless you save it in a session variable, cache, cookie etc.
What you can do instead of telling the user to redirect, is to call the view you want to show them yourself from within the same request (i.e. at the point you would issue the redirect) and then you could pass whatever you liked.