tornado cache

cache.py

# coding: utf-8


try:
    import cPickle as pickle
except ImportError:
    import pickle
try:
    import hashlib
    sha1 = hashlib.sha1
except ImportError:
    import sha
    sha1 = sha.new
import functools


def cache(expires=7200):
    def _func(func):
        @functools.wraps(func)
        def wrapper(handler, *args, **kwargs):
            handler.expires = expires
            return func(handler, *args, **kwargs)
        return wrapper
    return _func


class CacheMixin(object):

    @property
    def cache(self):
        return self.application.cache

    def prepare(self):
        super(CacheMixin, self).prepare()
        key = self._generate_key(self.request)
        print key
        if self.cache.exists(self._prefix(key)):
            rv = pickle.loads(self.cache.get(self._prefix(key)))
            self.write_cache(rv)
            self.finish()

    def _generate_key(self, request):
        key = pickle.dumps((request.path, request.arguments))
        return sha1(key).hexdigest()

    def _prefix(self, key):
        return "Cache:%s" % key

    def write_cache(self, chunk):
        super(CacheMixin, self).write(chunk)

    def write(self, chunk):
        pickled = pickle.dumps(chunk)
        key = self._generate_key(self.request)
        if hasattr(self, "expires"):
            self.cache.set(self._prefix(key), pickled, self.expires)
        else:
            self.cache.set(self._prefix(key), pickled)
        super(CacheMixin, self).write(chunk)


class CacheBackend(object):
    """
    The base Cache Backend class
    """

    def get(self, key):
        raise NotImplementedError

    def set(self, key, value, timeout):
        raise NotImplementedError

    def delitem(self, key):
        raise NotImplementedError

    def exists(self, key):
        raise NotImplementedError


class RedisCacheBackend(CacheBackend):

    def __init__(self, redis_connection, **options):
        self.options = dict(timeout=86400)
        self.options.update(options)

        self.redis = redis_connection

    def get(self, key):
        if self.exists(key):
            return self.redis.get(key)

        return None

    def set(self, key, value, timeout=None):
        self.redis.set(key, value)
        if timeout:
            self.redis.expire(key, timeout)
        else:
            self.redis.expire(key, self.options["timeout"])

    def delitem(self, key):

        self.redis.delete(key)

    def exists(self, key):
        print key

        return bool(self.redis.exists(key))

example.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import tornado.web
import tornado.ioloop
from cache import RedisCacheBackend, CacheMixin
import redis


class CacheHandler(CacheMixin, tornado.web.RequestHandler):
    def get(self):
        self.expires = 60   # set the cache expires
        self.write("test")

class Application(tornado.web.Application):

    def __init__(self):

        settings = dict(debug=True)
        self.redis = redis.Redis()

        self.cache = RedisCacheBackend(self.redis)
        handlers = [(r'/', CacheHandler)]
        super(Application, self).__init__(handlers=handlers, **settings)


if __name__ == '__main__':
    application = Application()
    application.listen(8080)
    tornado.ioloop.IOLoop.instance().start()

example_decorator.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import tornado.web
import tornado.ioloop
from cache import RedisCacheBackend, CacheMixin, cache
import redis

class BaseHandler(CacheMixin, RequestHandler):
    def prepare(self):
        super(BaseHandler, self).prepare()


class Greetandler(Cornado.web.RequestHandler):
    @cache(60) # set the cache expires
    def get(self):
        
        self.write("test")


class Application(tornado.web.Application):

    def __init__(self):

        settings = dict(debug=True)
        self.redis = redis.Redis()

        self.cache = RedisCacheBackend(self.redis)
        handlers = [(r'/', CacheHandler)]
        super(Application, self).__init__(handlers=handlers, **settings)


if __name__ == '__main__':
    application = Application()
    application.listen(8080)
    tornado.ioloop.IOLoop.instance().start()

有bug:
CacheMixin==>key = pickle.dumps((request.path, request.arguments))
可以改成:
CacheMixin==>key = pickle.dumps((request.path, request.method, request.arguments))

问题在于，如果一个url只有GET方式，但当有人恶意通过POST的方式访问的时候，页面返回错误信息，那么redis就会缓存这个错误信息“HTTPError: HTTP 403: Forbidden ('_xsrf' argument missing from POST)”。导致下次正常的GET方式，无法读取正确的内容（因为redis的key是存在的，value就是那个缓存的错误信息）

Hi @cloverstd, thank you for sharing this code. Could you please add a license for it? Can I share using GNU Affero General Public License?