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crawler: improve CacheHandler code

master
pictuga 2021-03-25 23:54:08 +01:00
parent 7342ab26d2
commit 6880a443e0
1 changed files with 45 additions and 61 deletions
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106
morss/crawler.py
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@ -456,6 +456,31 @@ class CacheHandler(BaseHandler):
def save(self, url, code, msg, headers, data, timestamp):
self.cache[url] = (code, msg, unicode(headers), data, timestamp)
def is_cached(self, url):
return self.load(url)[0] is not None
def cached_response(self, req):
# this does NOT check whether it's already cached, use with care
(code, msg, headers, data, timestamp) = self.load(req.get_full_url())
# return the cache as a response
resp = addinfourl(BytesIO(data), headers, req.get_full_url(), code)
resp.msg = msg
return resp
def save_response(self, req, resp):
data = resp.read()
self.save(req.get_full_url(), resp.code, resp.msg, resp.headers, data, time.time())
fp = BytesIO(data)
old_resp = resp
resp = addinfourl(fp, old_resp.headers, old_resp.url, old_resp.code)
resp.msg = old_resp.msg
return resp
def http_request(self, req):
(code, msg, headers, data, timestamp) = self.load(req.get_full_url())
@ -484,18 +509,13 @@ class CacheHandler(BaseHandler):
cache_age = time.time() - timestamp
# list in a simple way what to do when
if req.get_header('Morss') == 'from_304': # for whatever reason, we need an uppercase
# we're just in the middle of a dirty trick, use cache
pass
elif self.force_min == -2:
if self.force_min == -2:
if code is not None:
# already in cache, perfect, use cache
pass
return self.cached_response(req)
else:
# raise an error, via urllib handlers
headers['Morss'] = 'from_cache'
resp = addinfourl(BytesIO(), headers, req.get_full_url(), 409)
resp.msg = 'Conflict'
return resp
@ -506,7 +526,7 @@ class CacheHandler(BaseHandler):
elif self.force_min == -1:
# force use cache
pass
return self.cached_response(req)
elif self.force_min == 0:
# force refresh
@ -516,11 +536,9 @@ class CacheHandler(BaseHandler):
# "301 Moved Permanently" has to be cached...as long as we want
# (awesome HTTP specs), let's say a week (why not?). Use force_min=0
# if you want to bypass this (needed for a proper refresh)
pass
return self.cached_response(req)
elif self.force_min is None and ('no-cache' in cc_list
or 'no-store' in cc_list
or ('private' in cc_list and not self.private_cache)):
elif (self.force_min is None or self.force_min > 0) and ('no-cache' in cc_list or 'no-store' in cc_list or ('private' in cc_list and not self.private_cache)):
# kindly follow web servers indications, refresh
# if the same settings are used all along, this section shouldn't be
# of any use, since the page woudln't be cached in the first place
@ -529,76 +547,42 @@ class CacheHandler(BaseHandler):
elif 'max-age' in cc_values and int(cc_values['max-age']) > cache_age:
# server says it's still fine (and we trust him, if not, use force_min=0), use cache
pass
return self.cached_response(req)
elif self.force_min is not None and self.force_min > cache_age:
# still recent enough for us, use cache
pass
return self.cached_response(req)
else:
# according to the www, we have to refresh when nothing is said
return None
# return the cache as a response. This code is reached with 'pass' above
headers['morss'] = 'from_cache' # TODO delete the morss header from incoming pages, to avoid websites messing up with us
resp = addinfourl(BytesIO(data), headers, req.get_full_url(), code)
resp.msg = msg
return resp
def http_response(self, req, resp):
# code for after-fetch, to know whether to save to hard-drive (if stiking to http headers' will)
# NB. It might re-save requests pulled from cache, which will re-set the time() to the latest, i.e. lenghten its useful life
if resp.code == 304:
return resp
if resp.code == 304 and self.is_cached(resp.url):
# we are hopefully the first after the HTTP handler, so no need
# to re-run all the *_response
# here: cached page, returning from cache
return self.cached_response(req)
if ('cache-control' in resp.headers or 'pragma' in resp.headers) and self.force_min is None:
elif ('cache-control' in resp.headers or 'pragma' in resp.headers) and self.force_min is None:
cache_control = parse_http_list(resp.headers.get('cache-control', ()))
cache_control += parse_http_list(resp.headers.get('pragma', ()))
cc_list = [x for x in cache_control if '=' not in x]
if 'no-cache' in cc_list or 'no-store' in cc_list or ('private' in cc_list and not self.private_cache):
# kindly follow web servers indications
# kindly follow web servers indications (do not save & return)
return resp
if resp.headers.get('Morss') == 'from_cache':
# it comes from cache, so no need to save it again
return resp
else:
# save
return self.save_response(req, resp)
# save to disk
data = resp.read()
self.save(req.get_full_url(), resp.code, resp.msg, resp.headers, data, time.time())
# the below is only needed because of 'resp.read()' above, as we can't
# seek(0) on arbitraty file-like objects (e.g. sockets)
fp = BytesIO(data)
old_resp = resp
resp = addinfourl(fp, old_resp.headers, old_resp.url, old_resp.code)
resp.msg = old_resp.msg
return resp
def http_error_304(self, req, fp, code, msg, headers):
cache = list(self.load(req.get_full_url()))
if cache[0]:
cache[-1] = time.time()
self.save(req.get_full_url(), *cache)
new = Request(req.get_full_url(),
headers=req.headers,
unverifiable=True)
new.add_unredirected_header('Morss', 'from_304')
# create a "fake" new request to just re-run through the various
# handlers
return self.parent.open(new, timeout=req.timeout)
return None # when returning 'None', the next-available handler is used
# the 'HTTPRedirectHandler' has no 'handler_order', i.e.
# uses the default of 500, therefore executed after this
else:
return self.save_response(req, resp)
https_request = http_request
https_open = http_open