75 lines
2.0 KiB
Python
75 lines
2.0 KiB
Python
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# Per request cache middleware
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# Provides a simple cache dictionary only existing for the request's lifetime
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# The middleware provides a threadsafe LocMemCache which can be used just
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# like any other django cache facility
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from functools import wraps
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from threading import currentThread
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from django.core.cache.backends.locmem import LocMemCache
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_request_cache = {}
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_installed_middleware = False
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def get_request_cache():
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assert _installed_middleware, 'RequestCacheMiddleware not loaded'
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return _request_cache[currentThread()]
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def clear_request_cache():
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_request_cache[currentThread()].clear()
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class RequestCache(LocMemCache):
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def __init__(self):
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name = 'locmemcache@%i' % hash(currentThread())
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params = dict()
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super(RequestCache, self).__init__(name, params)
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class RequestCacheMiddleware(object):
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def __init__(self):
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global _installed_middleware
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_installed_middleware = True
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def process_request(self, request):
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cache = _request_cache.get(currentThread()) or RequestCache()
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_request_cache[currentThread()] = cache
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cache.clear()
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class request_cache(object):
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""" A decorator for use around functions that should be cached for the current
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request. Use like this:
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@request_cache()
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def cached(name):
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print "My name is %s and I'm cached" % name
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@request_cache(keyfn=lambda p: p['id'])
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def cached(param):
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print "My id is %s" % p['id']
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If no keyfn is provided the decorator expects the args to be hashable.
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"""
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def __init__(self, keyfn=None):
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self.keyfn = keyfn or (lambda *args: hash(args))
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def __call__(self, func):
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@wraps(func)
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def wrapper(*args, **kwargs):
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cache = get_request_cache()
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cachekey = self.keyfn(*args)
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cacheval = cache.get(cachekey, 'expired')
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if not cacheval == 'expired':
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return cacheval
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result = func(*args, **kwargs)
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cache.set(cachekey, result)
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return result
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return wrapper
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