import datetime from decimal import Decimal, ROUND_HALF_DOWN from django.contrib.syndication.views import Feed from django.core.cache import cache from django.db.models import Q from django.db.models.signals import post_save from django.utils.hashcompat import md5_constructor from django.views.decorators.http import condition from main.models import Arch, Repo, Package from news.models import News CACHE_TIMEOUT = 1800 CACHE_PACKAGE_KEY = 'cache_package_latest' CACHE_NEWS_KEY = 'cache_news_latest' def utc_offset(): '''Calculate the UTC offset from local time. Useful for converting values stored in local time to things like cache last modifed headers.''' timediff = datetime.datetime.utcnow() - datetime.datetime.now() secs = timediff.days * 86400 + timediff.seconds # round to nearest minute mins = Decimal(secs) / Decimal(60) mins = mins.quantize(Decimal('0'), rounding=ROUND_HALF_DOWN) return datetime.timedelta(minutes=int(mins)) def retrieve_package_latest(): # we could break this down based on the request url, but it would probably # cost us more in query time to do so. latest = cache.get(CACHE_PACKAGE_KEY) if latest: return latest try: latest = Package.objects.values('last_update').latest( 'last_update')['last_update'] latest = latest + utc_offset() cache.set(CACHE_PACKAGE_KEY, latest, CACHE_TIMEOUT) return latest except Package.DoesNotExist: pass return None def refresh_package_latest(**kwargs): # We could delete the value, but that could open a race condition # where the new data wouldn't have been committed yet by the calling # thread. Update it instead. latest = Package.objects.values('last_update').latest( 'last_update')['last_update'] latest = latest + utc_offset() cache.set(CACHE_PACKAGE_KEY, latest, CACHE_TIMEOUT) def package_etag(request, *args, **kwargs): latest = retrieve_package_latest() if latest: return md5_constructor(str(kwargs) + str(latest)).hexdigest() return None def package_last_modified(request, *args, **kwargs): return retrieve_package_latest() class PackageFeed(Feed): link = '/packages/' title_template = 'feeds/packages_title.html' description_template = 'feeds/packages_description.html' def __call__(self, request, *args, **kwargs): wrapper = condition(etag_func=package_etag, last_modified_func=package_last_modified) return wrapper(super(PackageFeed, self).__call__)(request, *args, **kwargs) def get_object(self, request, arch='', repo=''): obj = dict() qs = Package.objects.select_related('arch', 'repo').order_by('-last_update') if arch != '': # feed for a single arch, also include 'any' packages everywhere a = Arch.objects.get(name=arch) qs = qs.filter(Q(arch=a) | Q(arch__agnostic=True)) obj['arch'] = a if repo != '': # feed for a single arch AND repo r = Repo.objects.get(name=repo) qs = qs.filter(repo=r) obj['repo'] = r obj['qs'] = qs[:50] return obj def title(self, obj): s = 'Arch Linux: Recent package updates' if 'repo' in obj: s += ' (%s [%s])' % (obj['arch'].name, obj['repo'].name.lower()) elif 'arch' in obj: s += ' (%s)' % (obj['arch'].name) return s def description(self, obj): s = 'Recently updated packages in the Arch Linux package repositories' if 'arch' in obj: s += ' for the \'%s\' architecture' % obj['arch'].name.lower() if not obj['arch'].agnostic: s += ' (including \'any\' packages)' if 'repo' in obj: s += ' in the [%s] repository' % obj['repo'].name.lower() s += '.' return s def items(self, obj): return obj['qs'] def item_pubdate(self, item): return item.last_update def item_categories(self, item): return (item.repo.name, item.arch.name) def retrieve_news_latest(): latest = cache.get(CACHE_NEWS_KEY) if latest: return latest try: latest = News.objects.values('last_modified').latest( 'last_modified')['last_modified'] latest = latest + utc_offset() cache.set(CACHE_NEWS_KEY, latest, CACHE_TIMEOUT) return latest except News.DoesNotExist: pass return None def refresh_news_latest(**kwargs): # We could delete the value, but that could open a race condition # where the new data wouldn't have been committed yet by the calling # thread. Update it instead. latest = News.objects.values('last_modified').latest( 'last_modified')['last_modified'] latest = latest + utc_offset() cache.set(CACHE_NEWS_KEY, latest, CACHE_TIMEOUT) def news_etag(request, *args, **kwargs): latest = retrieve_news_latest() if latest: return md5_constructor(str(latest)).hexdigest() return None def news_last_modified(request, *args, **kwargs): return retrieve_news_latest() class NewsFeed(Feed): title = 'Arch Linux: Recent news updates' link = '/news/' description = 'The latest and greatest news from the Arch Linux distribution.' title_template = 'feeds/news_title.html' description_template = 'feeds/news_description.html' def __call__(self, request, *args, **kwargs): wrapper = condition(etag_func=news_etag, last_modified_func=news_last_modified) return wrapper(super(NewsFeed, self).__call__)(request, *args, **kwargs) def items(self): return News.objects.select_related('author').order_by('-postdate', '-id')[:10] def item_pubdate(self, item): d = item.postdate return datetime.datetime(d.year, d.month, d.day) def item_author_name(self, item): return item.author.get_full_name() # connect signals needed to keep cache in line with reality post_save.connect(refresh_package_latest, sender=Package) post_save.connect(refresh_news_latest, sender=News) # vim: set ts=4 sw=4 et: