Source code for scrapy.extensions.httpcache

import gzip
import logging
import os
import pickle
from email.utils import mktime_tz, parsedate_tz
from importlib import import_module
from time import time
from weakref import WeakKeyDictionary

from w3lib.http import headers_raw_to_dict, headers_dict_to_raw

from scrapy.http import Headers, Response
from scrapy.responsetypes import responsetypes
from scrapy.utils.httpobj import urlparse_cached
from scrapy.utils.project import data_path
from scrapy.utils.python import to_bytes, to_unicode
from scrapy.utils.request import request_fingerprint

logger = logging.getLogger(__name__)

[docs]class DummyPolicy: def __init__(self, settings): self.ignore_schemes = settings.getlist('HTTPCACHE_IGNORE_SCHEMES') self.ignore_http_codes = [int(x) for x in settings.getlist('HTTPCACHE_IGNORE_HTTP_CODES')] def should_cache_request(self, request): return urlparse_cached(request).scheme not in self.ignore_schemes def should_cache_response(self, response, request): return response.status not in self.ignore_http_codes def is_cached_response_fresh(self, cachedresponse, request): return True def is_cached_response_valid(self, cachedresponse, response, request): return True
[docs]class RFC2616Policy: MAXAGE = 3600 * 24 * 365 # one year def __init__(self, settings): self.always_store = settings.getbool('HTTPCACHE_ALWAYS_STORE') self.ignore_schemes = settings.getlist('HTTPCACHE_IGNORE_SCHEMES') self._cc_parsed = WeakKeyDictionary() self.ignore_response_cache_controls = [ to_bytes(cc) for cc in settings.getlist('HTTPCACHE_IGNORE_RESPONSE_CACHE_CONTROLS') ] def _parse_cachecontrol(self, r): if r not in self._cc_parsed: cch = r.headers.get(b'Cache-Control', b'') parsed = parse_cachecontrol(cch) if isinstance(r, Response): for key in self.ignore_response_cache_controls: parsed.pop(key, None) self._cc_parsed[r] = parsed return self._cc_parsed[r] def should_cache_request(self, request): if urlparse_cached(request).scheme in self.ignore_schemes: return False cc = self._parse_cachecontrol(request) # obey user-agent directive "Cache-Control: no-store" if b'no-store' in cc: return False # Any other is eligible for caching return True def should_cache_response(self, response, request): # What is cacheable - # Response cacheability - # Status code 206 is not included because cache can not deal with partial contents cc = self._parse_cachecontrol(response) # obey directive "Cache-Control: no-store" if b'no-store' in cc: return False # Never cache 304 (Not Modified) responses elif response.status == 304: return False # Cache unconditionally if configured to do so elif self.always_store: return True # Any hint on response expiration is good elif b'max-age' in cc or b'Expires' in response.headers: return True # Firefox fallbacks this statuses to one year expiration if none is set elif response.status in (300, 301, 308): return True # Other statuses without expiration requires at least one validator elif response.status in (200, 203, 401): return b'Last-Modified' in response.headers or b'ETag' in response.headers # Any other is probably not eligible for caching # Makes no sense to cache responses that does not contain expiration # info and can not be revalidated else: return False def is_cached_response_fresh(self, cachedresponse, request): cc = self._parse_cachecontrol(cachedresponse) ccreq = self._parse_cachecontrol(request) if b'no-cache' in cc or b'no-cache' in ccreq: return False now = time() freshnesslifetime = self._compute_freshness_lifetime(cachedresponse, request, now) currentage = self._compute_current_age(cachedresponse, request, now) reqmaxage = self._get_max_age(ccreq) if reqmaxage is not None: freshnesslifetime = min(freshnesslifetime, reqmaxage) if currentage < freshnesslifetime: return True if b'max-stale' in ccreq and b'must-revalidate' not in cc: # From RFC2616: "Indicates that the client is willing to # accept a response that has exceeded its expiration time. # If max-stale is assigned a value, then the client is # willing to accept a response that has exceeded its # expiration time by no more than the specified number of # seconds. If no value is assigned to max-stale, then the # client is willing to accept a stale response of any age." staleage = ccreq[b'max-stale'] if staleage is None: return True try: if currentage < freshnesslifetime + max(0, int(staleage)): return True except ValueError: pass # Cached response is stale, try to set validators if any self._set_conditional_validators(request, cachedresponse) return False def is_cached_response_valid(self, cachedresponse, response, request): # Use the cached response if the new response is a server error, # as long as the old response didn't specify must-revalidate. if response.status >= 500: cc = self._parse_cachecontrol(cachedresponse) if b'must-revalidate' not in cc: return True # Use the cached response if the server says it hasn't changed. return response.status == 304 def _set_conditional_validators(self, request, cachedresponse): if b'Last-Modified' in cachedresponse.headers: request.headers[b'If-Modified-Since'] = cachedresponse.headers[b'Last-Modified'] if b'ETag' in cachedresponse.headers: request.headers[b'If-None-Match'] = cachedresponse.headers[b'ETag'] def _get_max_age(self, cc): try: return max(0, int(cc[b'max-age'])) except (KeyError, ValueError): return None def _compute_freshness_lifetime(self, response, request, now): # Reference nsHttpResponseHead::ComputeFreshnessLifetime # cc = self._parse_cachecontrol(response) maxage = self._get_max_age(cc) if maxage is not None: return maxage # Parse date header or synthesize it if none exists date = rfc1123_to_epoch(response.headers.get(b'Date')) or now # Try HTTP/1.0 Expires header if b'Expires' in response.headers: expires = rfc1123_to_epoch(response.headers[b'Expires']) # When parsing Expires header fails RFC 2616 section 14.21 says we # should treat this as an expiration time in the past. return max(0, expires - date) if expires else 0 # Fallback to heuristic using last-modified header # This is not in RFC but on Firefox caching implementation lastmodified = rfc1123_to_epoch(response.headers.get(b'Last-Modified')) if lastmodified and lastmodified <= date: return (date - lastmodified) / 10 # This request can be cached indefinitely if response.status in (300, 301, 308): return self.MAXAGE # Insufficient information to compute fresshness lifetime return 0 def _compute_current_age(self, response, request, now): # Reference nsHttpResponseHead::ComputeCurrentAge # currentage = 0 # If Date header is not set we assume it is a fast connection, and # clock is in sync with the server date = rfc1123_to_epoch(response.headers.get(b'Date')) or now if now > date: currentage = now - date if b'Age' in response.headers: try: age = int(response.headers[b'Age']) currentage = max(currentage, age) except ValueError: pass return currentage
[docs]class DbmCacheStorage: def __init__(self, settings): self.cachedir = data_path(settings['HTTPCACHE_DIR'], createdir=True) self.expiration_secs = settings.getint('HTTPCACHE_EXPIRATION_SECS') self.dbmodule = import_module(settings['HTTPCACHE_DBM_MODULE']) self.db = None def open_spider(self, spider): dbpath = os.path.join(self.cachedir, '%s.db' % self.db =, 'c') logger.debug("Using DBM cache storage in %(cachepath)s" % {'cachepath': dbpath}, extra={'spider': spider}) def close_spider(self, spider): self.db.close() def retrieve_response(self, spider, request): data = self._read_data(spider, request) if data is None: return # not cached url = data['url'] status = data['status'] headers = Headers(data['headers']) body = data['body'] respcls = responsetypes.from_args(headers=headers, url=url) response = respcls(url=url, headers=headers, status=status, body=body) return response def store_response(self, spider, request, response): key = self._request_key(request) data = { 'status': response.status, 'url': response.url, 'headers': dict(response.headers), 'body': response.body, } self.db['%s_data' % key] = pickle.dumps(data, protocol=4) self.db['%s_time' % key] = str(time()) def _read_data(self, spider, request): key = self._request_key(request) db = self.db tkey = '%s_time' % key if tkey not in db: return # not found ts = db[tkey] if 0 < self.expiration_secs < time() - float(ts): return # expired return pickle.loads(db['%s_data' % key]) def _request_key(self, request): return request_fingerprint(request)
[docs]class FilesystemCacheStorage: def __init__(self, settings): self.cachedir = data_path(settings['HTTPCACHE_DIR']) self.expiration_secs = settings.getint('HTTPCACHE_EXPIRATION_SECS') self.use_gzip = settings.getbool('HTTPCACHE_GZIP') self._open = if self.use_gzip else open def open_spider(self, spider): logger.debug("Using filesystem cache storage in %(cachedir)s" % {'cachedir': self.cachedir}, extra={'spider': spider}) def close_spider(self, spider): pass def retrieve_response(self, spider, request): """Return response if present in cache, or None otherwise.""" metadata = self._read_meta(spider, request) if metadata is None: return # not cached rpath = self._get_request_path(spider, request) with self._open(os.path.join(rpath, 'response_body'), 'rb') as f: body = with self._open(os.path.join(rpath, 'response_headers'), 'rb') as f: rawheaders = url = metadata.get('response_url') status = metadata['status'] headers = Headers(headers_raw_to_dict(rawheaders)) respcls = responsetypes.from_args(headers=headers, url=url) response = respcls(url=url, headers=headers, status=status, body=body) return response def store_response(self, spider, request, response): """Store the given response in the cache.""" rpath = self._get_request_path(spider, request) if not os.path.exists(rpath): os.makedirs(rpath) metadata = { 'url': request.url, 'method': request.method, 'status': response.status, 'response_url': response.url, 'timestamp': time(), } with self._open(os.path.join(rpath, 'meta'), 'wb') as f: f.write(to_bytes(repr(metadata))) with self._open(os.path.join(rpath, 'pickled_meta'), 'wb') as f: pickle.dump(metadata, f, protocol=4) with self._open(os.path.join(rpath, 'response_headers'), 'wb') as f: f.write(headers_dict_to_raw(response.headers)) with self._open(os.path.join(rpath, 'response_body'), 'wb') as f: f.write(response.body) with self._open(os.path.join(rpath, 'request_headers'), 'wb') as f: f.write(headers_dict_to_raw(request.headers)) with self._open(os.path.join(rpath, 'request_body'), 'wb') as f: f.write(request.body) def _get_request_path(self, spider, request): key = request_fingerprint(request) return os.path.join(self.cachedir,, key[0:2], key) def _read_meta(self, spider, request): rpath = self._get_request_path(spider, request) metapath = os.path.join(rpath, 'pickled_meta') if not os.path.exists(metapath): return # not found mtime = os.stat(metapath).st_mtime if 0 < self.expiration_secs < time() - mtime: return # expired with self._open(metapath, 'rb') as f: return pickle.load(f)
def parse_cachecontrol(header): """Parse Cache-Control header >>> parse_cachecontrol(b'public, max-age=3600') == {b'public': None, ... b'max-age': b'3600'} True >>> parse_cachecontrol(b'') == {} True """ directives = {} for directive in header.split(b','): key, sep, val = directive.strip().partition(b'=') if key: directives[key.lower()] = val if sep else None return directives def rfc1123_to_epoch(date_str): try: date_str = to_unicode(date_str, encoding='ascii') return mktime_tz(parsedate_tz(date_str)) except Exception: return None