70 lines
3.4 KiB
Python
70 lines
3.4 KiB
Python
from django.http import (HttpResponse, HttpResponseNotModified,
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HttpResponseForbidden)
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from student.models import CourseEnrollment
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from xmodule.contentstore.django import contentstore
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from xmodule.contentstore.content import StaticContent, XASSET_LOCATION_TAG
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from xmodule.modulestore import InvalidLocationError
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from cache_toolbox.core import get_cached_content, set_cached_content
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from xmodule.exceptions import NotFoundError
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class StaticContentServer(object):
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def process_request(self, request):
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# look to see if the request is prefixed with 'c4x' tag
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if request.path.startswith('/' + XASSET_LOCATION_TAG + '/'):
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try:
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loc = StaticContent.get_location_from_path(request.path)
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except InvalidLocationError:
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# return a 'Bad Request' to browser as we have a malformed Location
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response = HttpResponse()
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response.status_code = 400
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return response
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# first look in our cache so we don't have to round-trip to the DB
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content = get_cached_content(loc)
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if content is None:
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# nope, not in cache, let's fetch from DB
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try:
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content = contentstore().find(loc, as_stream=True)
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except NotFoundError:
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response = HttpResponse()
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response.status_code = 404
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return response
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# since we fetched it from DB, let's cache it going forward, but only if it's < 1MB
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# this is because I haven't been able to find a means to stream data out of memcached
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if content.length is not None:
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if content.length < 1048576:
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# since we've queried as a stream, let's read in the stream into memory to set in cache
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content = content.copy_to_in_mem()
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set_cached_content(content)
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else:
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# NOP here, but we may wish to add a "cache-hit" counter in the future
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pass
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# Check that user has access to content
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if getattr(content, "locked", False):
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if not hasattr(request, "user") or not request.user.is_authenticated():
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return HttpResponseForbidden('Unauthorized')
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course_partial_id = "/".join([loc.org, loc.course])
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if not request.user.is_staff and not CourseEnrollment.is_enrolled_by_partial(
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request.user, course_partial_id):
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return HttpResponseForbidden('Unauthorized')
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# convert over the DB persistent last modified timestamp to a HTTP compatible
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# timestamp, so we can simply compare the strings
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last_modified_at_str = content.last_modified_at.strftime("%a, %d-%b-%Y %H:%M:%S GMT")
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# see if the client has cached this content, if so then compare the
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# timestamps, if they are the same then just return a 304 (Not Modified)
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if 'HTTP_IF_MODIFIED_SINCE' in request.META:
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if_modified_since = request.META['HTTP_IF_MODIFIED_SINCE']
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if if_modified_since == last_modified_at_str:
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return HttpResponseNotModified()
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response = HttpResponse(content.stream_data(), content_type=content.content_type)
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response['Last-Modified'] = last_modified_at_str
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return response
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