135 lines
6.8 KiB
Python
135 lines
6.8 KiB
Python
from django.http import (
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HttpResponse, HttpResponseNotModified, HttpResponseForbidden
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)
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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 opaque_keys import InvalidKeyError
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from opaque_keys.edx.locator import AssetLocator
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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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# TODO: Soon as we have a reasonable way to serialize/deserialize AssetKeys, we need
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# to change this file so instead of using course_id_partial, we're just using asset keys
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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 an asset prefix tag
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if (
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request.path.startswith('/' + XASSET_LOCATION_TAG + '/') or
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request.path.startswith('/' + AssetLocator.CANONICAL_NAMESPACE)
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):
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try:
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loc = StaticContent.get_location_from_path(request.path)
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except (InvalidLocationError, InvalidKeyError):
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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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if not request.user.is_staff:
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if getattr(loc, 'deprecated', False) and not CourseEnrollment.is_enrolled_by_partial(
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request.user, loc.course_key
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):
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return HttpResponseForbidden('Unauthorized')
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if not getattr(loc, 'deprecated', False) and not CourseEnrollment.is_enrolled(
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request.user, loc.course_key
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):
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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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# *** File streaming within a byte range ***
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# If a Range is provided, parse Range attribute of the request
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# Add Content-Range in the response if Range is structurally correct
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# Request -> Range attribute structure: "Range: bytes=first-[last]"
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# Response -> Content-Range attribute structure: "Content-Range: bytes first-last/totalLength"
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response = None
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if request.META.get('HTTP_RANGE'):
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# Data from cache (StaticContent) has no easy byte management, so we use the DB instead (StaticContentStream)
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if type(content) == StaticContent:
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content = contentstore().find(loc, as_stream=True)
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# Let's parse the Range header, bytes=first-[last]
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range_header = request.META['HTTP_RANGE']
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if '=' in range_header:
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unit, byte_range = range_header.split('=')
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# "Accept-Ranges: bytes" tells the user that only "bytes" ranges are allowed
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if unit == 'bytes' and '-' in byte_range:
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first, last = byte_range.split('-')
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# "first" must be a valid integer
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try:
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first = int(first)
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except ValueError:
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pass
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if type(first) is int:
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# "last" default value is the last byte of the file
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# Users can ask "bytes=0-" to request the whole file when they don't know the length
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try:
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last = int(last)
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except ValueError:
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last = content.length - 1
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if 0 <= first <= last < content.length:
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# Valid Range attribute
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response = HttpResponse(content.stream_data_in_range(first, last))
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response['Content-Range'] = 'bytes {first}-{last}/{length}'.format(
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first=first, last=last, length=content.length
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)
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response['Content-Length'] = str(last - first + 1)
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response.status_code = 206 # HTTP_206_PARTIAL_CONTENT
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if not response:
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# Malformed Range attribute
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response = HttpResponse()
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response.status_code = 400 # HTTP_400_BAD_REQUEST
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return response
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else:
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# No Range attribute
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response = HttpResponse(content.stream_data())
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response['Content-Length'] = content.length
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response['Accept-Ranges'] = 'bytes'
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response['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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