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import datetime
import threading
import time
import cherrypy
from cherrypy.lib import cptools, http
class MemoryCache:
def __init__(self):
self.clear()
t = threading.Thread(target=self.expireCache, name='expireCache')
self.expirationThread = t
t.setDaemon(True)
t.start()
def clear(self):
"""Reset the cache to its initial, empty state."""
self.cache = {}
self.expirations = {}
self.totPuts = 0
self.totGets = 0
self.totHits = 0
self.totExpires = 0
self.totNonModified = 0
self.cursize = 0
def _key(self):
return cherrypy.request.config.get("tools.caching.key", cherrypy.request.browser_url)
key = property(_key)
def expireCache(self):
# expireCache runs in a separate thread which the servers are
# not aware of. It's possible that "time" will be set to None
# arbitrarily, so we check "while time" to avoid exceptions.
# See tickets #99 and #180 for more information.
while time:
now = time.time()
for expirationTime, objects in self.expirations.items():
if expirationTime <= now:
for objSize, objKey in objects:
try:
del self.cache[objKey]
self.totExpires += 1
self.cursize -= objSize
except KeyError:
# the key may have been deleted elsewhere
pass
del self.expirations[expirationTime]
time.sleep(0.1)
def get(self):
"""Return the object if in the cache, else None."""
self.totGets += 1
cacheItem = self.cache.get(self.key, None)
if cacheItem:
self.totHits += 1
return cacheItem
else:
return None
def put(self, obj):
conf = cherrypy.request.config.get
if len(self.cache) < conf("tools.caching.maxobjects", 1000):
# Size check no longer includes header length
objSize = len(obj[2])
maxobjsize = conf("tools.caching.maxobjsize", 100000)
totalSize = self.cursize + objSize
maxsize = conf("tools.caching.maxsize", 10000000)
# checks if there's space for the object
if (objSize < maxobjsize and totalSize < maxsize):
# add to the expirations list and cache
expirationTime = time.time() + conf("tools.caching.delay", 600)
objKey = self.key
bucket = self.expirations.setdefault(expirationTime, [])
bucket.append((objSize, objKey))
self.cache[objKey] = obj
self.totPuts += 1
self.cursize = totalSize
def init(cache_class=None):
if cache_class is None:
cache_class = MemoryCache
cherrypy._cache = cache_class()
def get():
# Ignore POST, PUT, DELETE.
# See http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html#sec13.10.
invalid = cherrypy.config.get("tools.caching.invalid_methods",
("POST", "PUT", "DELETE"))
if cherrypy.request.method in invalid:
cherrypy.request.cached = c = False
else:
cacheData = cherrypy._cache.get()
cherrypy.request.cached = c = bool(cacheData)
if c:
response = cherrypy.response
s, response.headers, b, create_time = cacheData
# Add the required Age header
response.headers["Age"] = str(int(time.time() - create_time))
try:
cptools.validate_since()
except cherrypy.HTTPError, x:
if x.status == 304:
cherrypy._cache.totNonModified += 1
raise
# serve it & get out from the request
response.status = s
response.body = b
return c
def tee_output():
if cherrypy.request.cached:
return
response = cherrypy.response
output = []
def tee(body):
"""Tee response.body into a list."""
for chunk in body:
output.append(chunk)
yield chunk
# Might as well do this here; why cache if the body isn't consumed?
if response.headers.get('Pragma', None) != 'no-cache':
# save the cache data
body = ''.join([chunk for chunk in output])
create_time = time.time()
cherrypy._cache.put((response.status, response.headers or {},
body, create_time))
response.body = tee(response.body)
# CherryPy interfaces. Pick one.
def enable(**kwargs):
"""Compile-time decorator (turn on the tool in config)."""
def wrapper(f):
if not hasattr(f, "_cp_config"):
f._cp_config = {}
f._cp_config["tools.caching.on"] = True
for k, v in kwargs.iteritems():
f._cp_config["tools.caching." + k] = v
return f
return wrapper
def _wrapper():
if get():
cherrypy.request.handler = None
else:
# Note the devious technique here of adding hooks on the fly
cherrypy.request.hooks.attach('before_finalize', tee_output)
def _setup():
"""Hook caching into cherrypy.request using the given conf."""
conf = cherrypy.request.toolmap.get("caching", {})
if not getattr(cherrypy, "_cache", None):
init(conf.get("class", None))
cherrypy.request.hooks.attach('before_main', _wrapper)
def expires(secs=0, force=False):
"""Tool for influencing cache mechanisms using the 'Expires' header.
'secs' must be either an int or a datetime.timedelta, and indicates the
number of seconds between response.time and when the response should
expire. The 'Expires' header will be set to (response.time + secs).
If 'secs' is zero, the following "cache prevention" headers are also set:
'Pragma': 'no-cache'
'Cache-Control': 'no-cache'
If 'force' is False (the default), the following headers are checked:
'Etag', 'Last-Modified', 'Age', 'Expires'. If any are already present,
none of the "cache prevention" headers are set.
"""
if isinstance(secs, datetime.timedelta):
secs = (86400 * secs.days) + secs.seconds
expiry = http.HTTPDate(cherrypy.response.time + secs)
cptools.response_headers([("Expires", expiry)], force)
if secs == 0:
cacheable = False
if not force:
# some header names that indicate that the response can be cached
for indicator in ('Etag', 'Last-Modified', 'Age', 'Expires'):
if indicator in cherrypy.response.headers:
cacheable = True
break
if not cacheable:
cptools.response_headers([("Pragma", "no-cache")], force)
if cherrypy.request.version >= (1, 1):
cptools.response_headers([("Cache-Control", "no-cache")], force)
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