112 lines
3.7 KiB
Python
112 lines
3.7 KiB
Python
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import logging
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from coapthon.defines import Codes
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from coapthon.caching.cache import *
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__author__ = 'Emilio Vallati'
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logger = logging.getLogger(__name__)
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class CacheLayer(object):
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def __init__(self, mode, max_dim=2048):
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"""
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:param max_dim:
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"""
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self.cache = Cache(mode, max_dim)
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def receive_request(self, transaction):
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"""
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checks the cache for a response to the request
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:param transaction:
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:return:
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"""
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transaction.cached_element = self.cache.search_response(transaction.request)
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if transaction.cached_element is None:
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transaction.cacheHit = False
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else:
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transaction.response = transaction.cached_element.cached_response
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transaction.response.mid = transaction.request.mid
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transaction.cacheHit = True
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age = transaction.cached_element.creation_time + transaction.cached_element.max_age - time.time()
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if transaction.cached_element.freshness is True:
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if age <= 0:
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logger.debug("resource not fresh")
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"""
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if the resource is not fresh, its Etag must be added to the request so that the server might validate it instead of sending a new one
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"""
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transaction.cached_element.freshness = False
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"""
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ensuring that the request goes to the server
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"""
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transaction.cacheHit = False
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logger.debug("requesting etag %s", transaction.response.etag)
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transaction.request.etag = transaction.response.etag
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else:
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transaction.response.max_age = age
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else:
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transaction.cacheHit = False
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return transaction
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def send_response(self, transaction):
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"""
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updates the cache with the response if there was a cache miss
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:param transaction:
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:return:
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"""
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if transaction.cacheHit is False:
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"""
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handling response based on the code
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"""
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logger.debug("handling response")
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self._handle_response(transaction)
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return transaction
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def _handle_response(self, transaction):
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"""
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handles responses based on their type
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:param transaction:
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:return:
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"""
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code = transaction.response.code
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utils.check_code(code)
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"""
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VALID response:
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change the current cache value by switching the option set with the one provided
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also resets the timestamp
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if the request etag is different from the response, send the cached response
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"""
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if code == Codes.VALID.number:
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logger.debug("received VALID")
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self.cache.validate(transaction.request, transaction.response)
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if transaction.request.etag != transaction.response.etag:
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element = self.cache.search_response(transaction.request)
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transaction.response = element.cached_response
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return transaction
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"""
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CHANGED, CREATED or DELETED response:
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mark the requested resource as not fresh
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"""
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if code == Codes.CHANGED.number or code == Codes.CREATED.number or code == Codes.DELETED.number:
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target = self.cache.search_related(transaction.request)
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if target is not None:
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for element in target:
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self.cache.mark(element)
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return transaction
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"""
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any other response code can be cached normally
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"""
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self.cache.cache_add(transaction.request, transaction.response)
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return transaction
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