def __init__(self, filename, **options):
# Options
self.timeout = options.get('timeout', 60*30) # 30 minutes
self.ignore_environ = options.get('ignore_environ', True) # by default, ignore the environment variables
self.cache_true_only = options.get('cache_true_only', True)
self.salt = None
# Connect to the database
if not filename == ':memory:':
filename = self._normalize_filename(filename)
# TODO: Enforce 0600 perms on UNIX?
self.conn = sqlite3.connect(filename)
c = self.conn.cursor()
attempts = 0
while self.salt is None and attempts <= 1:
try:
c.execute("CREATE TABLE cache (key TEXT UNIQUE, value TEXT, expiration INTEGER);")
except sqlite3.OperationalError:
# Cache table exists
c.execute('DELETE FROM cache WHERE expiration < ?;', (time.time(),))
c.execute("SELECT value FROM cache WHERE key = ? LIMIT 1;", (Cache.SALT_NAME, ))
for row in c:
self.salt = decode_value(row[0])
else:
# Cache table just created
salt = os.urandom(hmac.HMAC.blocksize) # Default: 512-bit HMAC
c.execute("CREATE INDEX IF NOT EXISTS expiration ON cache (expiration ASC);")
c.execute('INSERT INTO cache(key, value) VALUES (?, ?);', (Cache.SALT_NAME, encode_value(salt)))
finally:
self.conn.commit()
attempts += 1
assert self.salt is not None, "wsgi_googleauth Error: Salt not initialized"
def wrapper(*args):
# Invariant: cache is sorted by timeout
# Requirement: time.time is a monotonically increasing function
c = self.conn.cursor()
# Generate Key
hash_args = args[1:] if self.ignore_environ else args[:]
key = hmac.new(self.salt, encode_value(hash_args), digestmod=hashlib.sha256).hexdigest()
# Cache Lookup
found = False
c.execute("SELECT value FROM cache WHERE key = ? AND expiration > ? LIMIT 1;", (key, time.time()))
for row in c:
result = decode_value(row[0])
found = True
# Query Function
if not found:
result = f(*args)
if not self.cache_true_only or (self.cache_true_only and result is True):
timeout = time.time() + self.timeout
try:
c.execute("INSERT INTO cache(key, value, expiration) VALUES (?, ?, ?);", (key, encode_value(result), timeout))
except sqlite3.IntegrityError:
c.execute("UPDATE cache SET expiration = ? WHERE key = ?;", (timeout, key))
self.conn.commit()
return result
