"""Session implementation for CherryPy. We use cherrypy.request to store some convenient variables as well as data about the session for the current request. Instead of polluting cherrypy.request we use a Session object bound to cherrypy.session to store these variables. """ import datetime import os try: import cPickle as pickle except ImportError: import pickle import random import sha import time import threading import types from warnings import warn import cherrypy from cherrypy.lib import http class PerpetualTimer(threading._Timer): def run(self): while True: self.finished.wait(self.interval) if self.finished.isSet(): return self.function(*self.args, **self.kwargs) missing = object() class Session(object): """A CherryPy dict-like Session object (one per request).""" __metaclass__ = cherrypy._AttributeDocstrings id = None id__doc = "The current session ID." timeout = 60 timeout__doc = "Number of minutes after which to delete session data." locked = False locked__doc = """ If True, this session instance has exclusive read/write access to session data.""" loaded = False loaded__doc = """ If True, data has been retrieved from storage. This should happen automatically on the first attempt to access session data.""" clean_thread = None clean_thread__doc = "Class-level PerpetualTimer which calls self.clean_up." clean_freq = 5 clean_freq__doc = "The poll rate for expired session cleanup in minutes." def __init__(self, id=None, **kwargs): self._data = {} for k, v in kwargs.iteritems(): setattr(self, k, v) self.id = id while self.id is None: self.id = self.generate_id() # Assert that the generated id is not already stored. if self._load() is not None: self.id = None def clean_interrupt(cls): """Stop the expired-session cleaning timer.""" if cls.clean_thread: cls.clean_thread.cancel() cls.clean_thread.join() cls.clean_thread = None clean_interrupt = classmethod(clean_interrupt) def clean_up(self): """Clean up expired sessions.""" pass try: os.urandom(20) except (AttributeError, NotImplementedError): # os.urandom not available until Python 2.4. Fall back to random.random. def generate_id(self): """Return a new session id.""" return sha.new('%s' % random.random()).hexdigest() else: def generate_id(self): """Return a new session id.""" return os.urandom(20).encode('hex') def save(self): """Save session data.""" try: # If session data has never been loaded then it's never been # accessed: no need to delete it if self.loaded: t = datetime.timedelta(seconds = self.timeout * 60) expiration_time = datetime.datetime.now() + t self._save(expiration_time) finally: if self.locked: # Always release the lock if the user didn't release it self.release_lock() def load(self): """Copy stored session data into this session instance.""" data = self._load() # data is either None or a tuple (session_data, expiration_time) if data is None or data[1] < datetime.datetime.now(): # Expired session: flush session data (but keep the same id) self._data = {} else: self._data = data[0] self.loaded = True # Stick the clean_thread in the class, not the instance. # The instances are created and destroyed per-request. cls = self.__class__ if not cls.clean_thread: cherrypy.engine.on_stop_engine_list.append(cls.clean_interrupt) # clean_up is in instancemethod and not a classmethod, # so tool config can be accessed inside the method. t = PerpetualTimer(self.clean_freq, self.clean_up) t.setName("CP Session Cleanup") cls.clean_thread = t t.start() def delete(self): """Delete stored session data.""" self._delete() def __getitem__(self, key): if not self.loaded: self.load() return self._data[key] def __setitem__(self, key, value): if not self.loaded: self.load() self._data[key] = value def __delitem__(self, key): if not self.loaded: self.load() del self._data[key] def pop(self, key, default=missing): if not self.loaded: self.load() if default is missing: return self._data.pop(key) else: return self._data.pop(key, default) def __contains__(self, key): if not self.loaded: self.load() return key in self._data def has_key(self, key): if not self.loaded: self.load() return self._data.has_key(key) def get(self, key, default=None): if not self.loaded: self.load() return self._data.get(key, default) def update(self, d): if not self.loaded: self.load() self._data.update(d) def setdefault(self, key, default=None): if not self.loaded: self.load() return self._data.setdefault(key, default) def clear(self): if not self.loaded: self.load() self._data.clear() def keys(self): if not self.loaded: self.load() return self._data.keys() def items(self): if not self.loaded: self.load() return self._data.items() def values(self): if not self.loaded: self.load() return self._data.values() class RamSession(Session): # Class-level objects. Don't rebind these! cache = {} locks = {} def clean_up(self): """Clean up expired sessions.""" now = datetime.datetime.now() for id, (data, expiration_time) in self.cache.items(): if expiration_time < now: try: del self.cache[id] except KeyError: pass try: del self.locks[id] except KeyError: pass def _load(self): return self.cache.get(self.id) def _save(self, expiration_time): self.cache[self.id] = (self._data, expiration_time) def _delete(self): del self.cache[self.id] def acquire_lock(self): self.locked = True self.locks.setdefault(self.id, threading.RLock()).acquire() def release_lock(self): self.locks[self.id].release() self.locked = False class FileSession(Session): """ Implementation of the File backend for sessions storage_path: the folder where session data will be saved. Each session will be saved as pickle.dump(data, expiration_time) in its own file; the filename will be self.SESSION_PREFIX + self.id. """ SESSION_PREFIX = 'session-' LOCK_SUFFIX = '.lock' def setup(self): # Warn if any lock files exist at startup. lockfiles = [fname for fname in os.listdir(self.storage_path) if (fname.startswith(self.SESSION_PREFIX) and fname.endswith(self.LOCK_SUFFIX))] if lockfiles: plural = ('', 's')[len(lockfiles) > 1] warn("%s session lockfile%s found at startup. If you are " "only running one process, then you may need to " "manually delete the lockfiles found at %r." % (len(lockfiles), plural, os.path.abspath(self.storage_path))) def _get_file_path(self): return os.path.join(self.storage_path, self.SESSION_PREFIX + self.id) def _load(self, path=None): if path is None: path = self._get_file_path() try: f = open(path, "rb") try: return pickle.load(f) finally: f.close() except (IOError, EOFError): return None def _save(self, expiration_time): f = open(self._get_file_path(), "wb") try: pickle.dump((self._data, expiration_time), f) finally: f.close() def _delete(self): try: os.unlink(self._get_file_path()) except OSError: pass def acquire_lock(self, path=None): if path is None: path = self._get_file_path() path += self.LOCK_SUFFIX while True: try: lockfd = os.open(path, os.O_CREAT|os.O_WRONLY|os.O_EXCL) except OSError: time.sleep(0.1) else: os.close(lockfd) break self.locked = True def release_lock(self, path=None): if path is None: path = self._get_file_path() os.unlink(path + self.LOCK_SUFFIX) self.locked = False def clean_up(self): """Clean up expired sessions.""" now = datetime.datetime.now() # Iterate over all session files in self.storage_path for fname in os.listdir(self.storage_path): if (fname.startswith(self.SESSION_PREFIX) and not fname.endswith(self.LOCK_SUFFIX)): # We have a session file: lock and load it and check # if it's expired. If it fails, nevermind. path = os.path.join(self.storage_path, fname) self.acquire_lock(path) try: contents = self._load(path) # _load returns None on IOError if contents is not None: data, expiration_time = contents if expiration_time < now: # Session expired: deleting it os.unlink(path) finally: self.release_lock(path) class PostgresqlSession(Session): """ Implementation of the PostgreSQL backend for sessions. It assumes a table like this: create table session ( id varchar(40), data text, expiration_time timestamp ) You must provide your own get_db function. """ def __init__(self): self.db = self.get_db() self.cursor = self.db.cursor() def __del__(self): if self.cursor: self.cursor.close() self.db.commit() def _load(self): # Select session data from table self.cursor.execute('select data, expiration_time from session ' 'where id=%s', (self.id,)) rows = self.cursor.fetchall() if not rows: return None pickled_data, expiration_time = rows[0] data = pickle.loads(pickled_data) return data, expiration_time def _save(self, expiration_time): pickled_data = pickle.dumps(self._data) self.cursor.execute('update session set data = %s, ' 'expiration_time = %s where id = %s', (pickled_data, expiration_time, self.id)) def _delete(self): self.cursor.execute('delete from session where id=%s', (self.id,)) def acquire_lock(self): # We use the "for update" clause to lock the row self.locked = True self.cursor.execute('select id from session where id=%s for update', (self.id,)) def release_lock(self): # We just close the cursor and that will remove the lock # introduced by the "for update" clause self.cursor.close() self.locked = False def clean_up(self): """Clean up expired sessions.""" self.cursor.execute('delete from session where expiration_time < %s', (datetime.datetime.now(),)) # Hook functions (for CherryPy tools) def save(): """Save any changed session data.""" # Guard against running twice if hasattr(cherrypy.request, "_sessionsaved"): return cherrypy.request._sessionsaved = True if cherrypy.response.stream: # If the body is being streamed, we have to save the data # *after* the response has been written out cherrypy.request.hooks.attach('on_end_request', cherrypy.session.save) else: # If the body is not being streamed, we save the data now # (so we can release the lock). if isinstance(cherrypy.response.body, types.GeneratorType): cherrypy.response.collapse_body() cherrypy.session.save() save.failsafe = True def close(): """Close the session object for this request.""" sess = cherrypy.session if sess.locked: # If the session is still locked we release the lock sess.release_lock() close.failsafe = True close.priority = 90 def init(storage_type='ram', path=None, path_header=None, name='session_id', timeout=60, domain=None, secure=False, clean_freq=5, **kwargs): """Initialize session object (using cookies). storage_type: one of 'ram', 'file', 'postgresql'. This will be used to look up the corresponding class in cherrypy.lib.sessions globals. For example, 'file' will use the FileSession class. path: the 'path' value to stick in the response cookie metadata. path_header: if 'path' is None (the default), then the response cookie 'path' will be pulled from request.headers[path_header]. name: the name of the cookie. timeout: the expiration timeout for the cookie. domain: the cookie domain. secure: if False (the default) the cookie 'secure' value will not be set. If True, the cookie 'secure' value will be set (to 1). clean_freq (minutes): the poll rate for expired session cleanup. Any additional kwargs will be bound to the new Session instance, and may be specific to the storage type. See the subclass of Session you're using for more information. """ request = cherrypy.request # Guard against running twice if hasattr(request, "_session_init_flag"): return request._session_init_flag = True # Check if request came with a session ID id = None if name in request.cookie: id = request.cookie[name].value # Create and attach a new Session instance to cherrypy._serving. # It will possess a reference to (and lock, and lazily load) # the requested session data. storage_class = storage_type.title() + 'Session' kwargs['timeout'] = timeout kwargs['clean_freq'] = clean_freq cherrypy._serving.session = sess = globals()[storage_class](id, **kwargs) if not hasattr(cherrypy, "session"): cherrypy.session = cherrypy._ThreadLocalProxy('session') if hasattr(sess, "setup"): sess.setup() # Set response cookie cookie = cherrypy.response.cookie cookie[name] = sess.id cookie[name]['path'] = path or request.headers.get(path_header) or '/' # We'd like to use the "max-age" param as indicated in # http://www.faqs.org/rfcs/rfc2109.html but IE doesn't # save it to disk and the session is lost if people close # the browser. So we have to use the old "expires" ... sigh ... ## cookie[name]['max-age'] = timeout * 60 if timeout: cookie[name]['expires'] = http.HTTPDate(time.time() + (timeout * 60)) if domain is not None: cookie[name]['domain'] = domain if secure: cookie[name]['secure'] = 1 def expire(): """Expire the current session cookie.""" name = cherrypy.request.config.get('tools.sessions.name', 'session_id') one_year = 60 * 60 * 24 * 365 exp = time.gmtime(time.time() - one_year) t = time.strftime("%a, %d-%b-%Y %H:%M:%S GMT", exp) cherrypy.response.cookie[name]['expires'] = t