|
|
import sys
|
|
|
import threading
|
|
|
import weakref
|
|
|
from base64 import b64encode
|
|
|
from logging import getLogger
|
|
|
from os import urandom
|
|
|
|
|
|
from redis import StrictRedis
|
|
|
|
|
|
__version__ = '3.7.0'
|
|
|
|
|
|
loggers = {
|
|
|
k: getLogger("vcsserver." + ".".join((__name__, k)))
|
|
|
for k in [
|
|
|
"acquire",
|
|
|
"refresh.thread.start",
|
|
|
"refresh.thread.stop",
|
|
|
"refresh.thread.exit",
|
|
|
"refresh.start",
|
|
|
"refresh.shutdown",
|
|
|
"refresh.exit",
|
|
|
"release",
|
|
|
]
|
|
|
}
|
|
|
|
|
|
PY3 = sys.version_info[0] == 3
|
|
|
|
|
|
if PY3:
|
|
|
text_type = str
|
|
|
binary_type = bytes
|
|
|
else:
|
|
|
text_type = unicode # noqa
|
|
|
binary_type = str
|
|
|
|
|
|
|
|
|
# Check if the id match. If not, return an error code.
|
|
|
UNLOCK_SCRIPT = b"""
|
|
|
if redis.call("get", KEYS[1]) ~= ARGV[1] then
|
|
|
return 1
|
|
|
else
|
|
|
redis.call("del", KEYS[2])
|
|
|
redis.call("lpush", KEYS[2], 1)
|
|
|
redis.call("pexpire", KEYS[2], ARGV[2])
|
|
|
redis.call("del", KEYS[1])
|
|
|
return 0
|
|
|
end
|
|
|
"""
|
|
|
|
|
|
# Covers both cases when key doesn't exist and doesn't equal to lock's id
|
|
|
EXTEND_SCRIPT = b"""
|
|
|
if redis.call("get", KEYS[1]) ~= ARGV[1] then
|
|
|
return 1
|
|
|
elseif redis.call("ttl", KEYS[1]) < 0 then
|
|
|
return 2
|
|
|
else
|
|
|
redis.call("expire", KEYS[1], ARGV[2])
|
|
|
return 0
|
|
|
end
|
|
|
"""
|
|
|
|
|
|
RESET_SCRIPT = b"""
|
|
|
redis.call('del', KEYS[2])
|
|
|
redis.call('lpush', KEYS[2], 1)
|
|
|
redis.call('pexpire', KEYS[2], ARGV[2])
|
|
|
return redis.call('del', KEYS[1])
|
|
|
"""
|
|
|
|
|
|
RESET_ALL_SCRIPT = b"""
|
|
|
local locks = redis.call('keys', 'lock:*')
|
|
|
local signal
|
|
|
for _, lock in pairs(locks) do
|
|
|
signal = 'lock-signal:' .. string.sub(lock, 6)
|
|
|
redis.call('del', signal)
|
|
|
redis.call('lpush', signal, 1)
|
|
|
redis.call('expire', signal, 1)
|
|
|
redis.call('del', lock)
|
|
|
end
|
|
|
return #locks
|
|
|
"""
|
|
|
|
|
|
|
|
|
class AlreadyAcquired(RuntimeError):
|
|
|
pass
|
|
|
|
|
|
|
|
|
class NotAcquired(RuntimeError):
|
|
|
pass
|
|
|
|
|
|
|
|
|
class AlreadyStarted(RuntimeError):
|
|
|
pass
|
|
|
|
|
|
|
|
|
class TimeoutNotUsable(RuntimeError):
|
|
|
pass
|
|
|
|
|
|
|
|
|
class InvalidTimeout(RuntimeError):
|
|
|
pass
|
|
|
|
|
|
|
|
|
class TimeoutTooLarge(RuntimeError):
|
|
|
pass
|
|
|
|
|
|
|
|
|
class NotExpirable(RuntimeError):
|
|
|
pass
|
|
|
|
|
|
|
|
|
class Lock(object):
|
|
|
"""
|
|
|
A Lock context manager implemented via redis SETNX/BLPOP.
|
|
|
"""
|
|
|
unlock_script = None
|
|
|
extend_script = None
|
|
|
reset_script = None
|
|
|
reset_all_script = None
|
|
|
|
|
|
def __init__(self, redis_client, name, expire=None, id=None, auto_renewal=False, strict=True, signal_expire=1000):
|
|
|
"""
|
|
|
:param redis_client:
|
|
|
An instance of :class:`~StrictRedis`.
|
|
|
:param name:
|
|
|
The name (redis key) the lock should have.
|
|
|
:param expire:
|
|
|
The lock expiry time in seconds. If left at the default (None)
|
|
|
the lock will not expire.
|
|
|
:param id:
|
|
|
The ID (redis value) the lock should have. A random value is
|
|
|
generated when left at the default.
|
|
|
|
|
|
Note that if you specify this then the lock is marked as "held". Acquires
|
|
|
won't be possible.
|
|
|
:param auto_renewal:
|
|
|
If set to ``True``, Lock will automatically renew the lock so that it
|
|
|
doesn't expire for as long as the lock is held (acquire() called
|
|
|
or running in a context manager).
|
|
|
|
|
|
Implementation note: Renewal will happen using a daemon thread with
|
|
|
an interval of ``expire*2/3``. If wishing to use a different renewal
|
|
|
time, subclass Lock, call ``super().__init__()`` then set
|
|
|
``self._lock_renewal_interval`` to your desired interval.
|
|
|
:param strict:
|
|
|
If set ``True`` then the ``redis_client`` needs to be an instance of ``redis.StrictRedis``.
|
|
|
:param signal_expire:
|
|
|
Advanced option to override signal list expiration in milliseconds. Increase it for very slow clients. Default: ``1000``.
|
|
|
"""
|
|
|
if strict and not isinstance(redis_client, StrictRedis):
|
|
|
raise ValueError("redis_client must be instance of StrictRedis. "
|
|
|
"Use strict=False if you know what you're doing.")
|
|
|
if auto_renewal and expire is None:
|
|
|
raise ValueError("Expire may not be None when auto_renewal is set")
|
|
|
|
|
|
self._client = redis_client
|
|
|
|
|
|
if expire:
|
|
|
expire = int(expire)
|
|
|
if expire < 0:
|
|
|
raise ValueError("A negative expire is not acceptable.")
|
|
|
else:
|
|
|
expire = None
|
|
|
self._expire = expire
|
|
|
|
|
|
self._signal_expire = signal_expire
|
|
|
if id is None:
|
|
|
self._id = b64encode(urandom(18)).decode('ascii')
|
|
|
elif isinstance(id, binary_type):
|
|
|
try:
|
|
|
self._id = id.decode('ascii')
|
|
|
except UnicodeDecodeError:
|
|
|
self._id = b64encode(id).decode('ascii')
|
|
|
elif isinstance(id, text_type):
|
|
|
self._id = id
|
|
|
else:
|
|
|
raise TypeError("Incorrect type for `id`. Must be bytes/str not %s." % type(id))
|
|
|
self._name = 'lock:' + name
|
|
|
self._signal = 'lock-signal:' + name
|
|
|
self._lock_renewal_interval = (float(expire) * 2 / 3
|
|
|
if auto_renewal
|
|
|
else None)
|
|
|
self._lock_renewal_thread = None
|
|
|
|
|
|
self.register_scripts(redis_client)
|
|
|
|
|
|
@classmethod
|
|
|
def register_scripts(cls, redis_client):
|
|
|
global reset_all_script
|
|
|
if reset_all_script is None:
|
|
|
reset_all_script = redis_client.register_script(RESET_ALL_SCRIPT)
|
|
|
cls.unlock_script = redis_client.register_script(UNLOCK_SCRIPT)
|
|
|
cls.extend_script = redis_client.register_script(EXTEND_SCRIPT)
|
|
|
cls.reset_script = redis_client.register_script(RESET_SCRIPT)
|
|
|
cls.reset_all_script = redis_client.register_script(RESET_ALL_SCRIPT)
|
|
|
|
|
|
@property
|
|
|
def _held(self):
|
|
|
return self.id == self.get_owner_id()
|
|
|
|
|
|
def reset(self):
|
|
|
"""
|
|
|
Forcibly deletes the lock. Use this with care.
|
|
|
"""
|
|
|
self.reset_script(client=self._client, keys=(self._name, self._signal), args=(self.id, self._signal_expire))
|
|
|
|
|
|
@property
|
|
|
def id(self):
|
|
|
return self._id
|
|
|
|
|
|
def get_owner_id(self):
|
|
|
owner_id = self._client.get(self._name)
|
|
|
if isinstance(owner_id, binary_type):
|
|
|
owner_id = owner_id.decode('ascii', 'replace')
|
|
|
return owner_id
|
|
|
|
|
|
def acquire(self, blocking=True, timeout=None):
|
|
|
"""
|
|
|
:param blocking:
|
|
|
Boolean value specifying whether lock should be blocking or not.
|
|
|
:param timeout:
|
|
|
An integer value specifying the maximum number of seconds to block.
|
|
|
"""
|
|
|
logger = loggers["acquire"]
|
|
|
|
|
|
logger.debug("Getting blocking: %s acquire on %r ...", blocking, self._name)
|
|
|
|
|
|
if self._held:
|
|
|
owner_id = self.get_owner_id()
|
|
|
raise AlreadyAcquired("Already acquired from this Lock instance. Lock id: {}".format(owner_id))
|
|
|
|
|
|
if not blocking and timeout is not None:
|
|
|
raise TimeoutNotUsable("Timeout cannot be used if blocking=False")
|
|
|
|
|
|
if timeout:
|
|
|
timeout = int(timeout)
|
|
|
if timeout < 0:
|
|
|
raise InvalidTimeout("Timeout (%d) cannot be less than or equal to 0" % timeout)
|
|
|
|
|
|
if self._expire and not self._lock_renewal_interval and timeout > self._expire:
|
|
|
raise TimeoutTooLarge("Timeout (%d) cannot be greater than expire (%d)" % (timeout, self._expire))
|
|
|
|
|
|
busy = True
|
|
|
blpop_timeout = timeout or self._expire or 0
|
|
|
timed_out = False
|
|
|
while busy:
|
|
|
busy = not self._client.set(self._name, self._id, nx=True, ex=self._expire)
|
|
|
if busy:
|
|
|
if timed_out:
|
|
|
return False
|
|
|
elif blocking:
|
|
|
timed_out = not self._client.blpop(self._signal, blpop_timeout) and timeout
|
|
|
else:
|
|
|
logger.warning("Failed to get %r.", self._name)
|
|
|
return False
|
|
|
|
|
|
logger.debug("Got lock for %r.", self._name)
|
|
|
if self._lock_renewal_interval is not None:
|
|
|
self._start_lock_renewer()
|
|
|
return True
|
|
|
|
|
|
def extend(self, expire=None):
|
|
|
"""Extends expiration time of the lock.
|
|
|
|
|
|
:param expire:
|
|
|
New expiration time. If ``None`` - `expire` provided during
|
|
|
lock initialization will be taken.
|
|
|
"""
|
|
|
if expire:
|
|
|
expire = int(expire)
|
|
|
if expire < 0:
|
|
|
raise ValueError("A negative expire is not acceptable.")
|
|
|
elif self._expire is not None:
|
|
|
expire = self._expire
|
|
|
else:
|
|
|
raise TypeError(
|
|
|
"To extend a lock 'expire' must be provided as an "
|
|
|
"argument to extend() method or at initialization time."
|
|
|
)
|
|
|
|
|
|
error = self.extend_script(client=self._client, keys=(self._name, self._signal), args=(self._id, expire))
|
|
|
if error == 1:
|
|
|
raise NotAcquired("Lock %s is not acquired or it already expired." % self._name)
|
|
|
elif error == 2:
|
|
|
raise NotExpirable("Lock %s has no assigned expiration time" % self._name)
|
|
|
elif error:
|
|
|
raise RuntimeError("Unsupported error code %s from EXTEND script" % error)
|
|
|
|
|
|
@staticmethod
|
|
|
def _lock_renewer(lockref, interval, stop):
|
|
|
"""
|
|
|
Renew the lock key in redis every `interval` seconds for as long
|
|
|
as `self._lock_renewal_thread.should_exit` is False.
|
|
|
"""
|
|
|
while not stop.wait(timeout=interval):
|
|
|
loggers["refresh.thread.start"].debug("Refreshing lock")
|
|
|
lock = lockref()
|
|
|
if lock is None:
|
|
|
loggers["refresh.thread.stop"].debug(
|
|
|
"The lock no longer exists, stopping lock refreshing"
|
|
|
)
|
|
|
break
|
|
|
lock.extend(expire=lock._expire)
|
|
|
del lock
|
|
|
loggers["refresh.thread.exit"].debug("Exit requested, stopping lock refreshing")
|
|
|
|
|
|
def _start_lock_renewer(self):
|
|
|
"""
|
|
|
Starts the lock refresher thread.
|
|
|
"""
|
|
|
if self._lock_renewal_thread is not None:
|
|
|
raise AlreadyStarted("Lock refresh thread already started")
|
|
|
|
|
|
loggers["refresh.start"].debug(
|
|
|
"Starting thread to refresh lock every %s seconds",
|
|
|
self._lock_renewal_interval
|
|
|
)
|
|
|
self._lock_renewal_stop = threading.Event()
|
|
|
self._lock_renewal_thread = threading.Thread(
|
|
|
group=None,
|
|
|
target=self._lock_renewer,
|
|
|
kwargs={'lockref': weakref.ref(self),
|
|
|
'interval': self._lock_renewal_interval,
|
|
|
'stop': self._lock_renewal_stop}
|
|
|
)
|
|
|
self._lock_renewal_thread.setDaemon(True)
|
|
|
self._lock_renewal_thread.start()
|
|
|
|
|
|
def _stop_lock_renewer(self):
|
|
|
"""
|
|
|
Stop the lock renewer.
|
|
|
|
|
|
This signals the renewal thread and waits for its exit.
|
|
|
"""
|
|
|
if self._lock_renewal_thread is None or not self._lock_renewal_thread.is_alive():
|
|
|
return
|
|
|
loggers["refresh.shutdown"].debug("Signalling the lock refresher to stop")
|
|
|
self._lock_renewal_stop.set()
|
|
|
self._lock_renewal_thread.join()
|
|
|
self._lock_renewal_thread = None
|
|
|
loggers["refresh.exit"].debug("Lock refresher has stopped")
|
|
|
|
|
|
def __enter__(self):
|
|
|
acquired = self.acquire(blocking=True)
|
|
|
assert acquired, "Lock wasn't acquired, but blocking=True"
|
|
|
return self
|
|
|
|
|
|
def __exit__(self, exc_type=None, exc_value=None, traceback=None):
|
|
|
self.release()
|
|
|
|
|
|
def release(self):
|
|
|
"""Releases the lock, that was acquired with the same object.
|
|
|
|
|
|
.. note::
|
|
|
|
|
|
If you want to release a lock that you acquired in a different place you have two choices:
|
|
|
|
|
|
* Use ``Lock("name", id=id_from_other_place).release()``
|
|
|
* Use ``Lock("name").reset()``
|
|
|
"""
|
|
|
if self._lock_renewal_thread is not None:
|
|
|
self._stop_lock_renewer()
|
|
|
loggers["release"].debug("Releasing %r.", self._name)
|
|
|
error = self.unlock_script(client=self._client, keys=(self._name, self._signal), args=(self._id, self._signal_expire))
|
|
|
if error == 1:
|
|
|
raise NotAcquired("Lock %s is not acquired or it already expired." % self._name)
|
|
|
elif error:
|
|
|
raise RuntimeError("Unsupported error code %s from EXTEND script." % error)
|
|
|
|
|
|
def locked(self):
|
|
|
"""
|
|
|
Return true if the lock is acquired.
|
|
|
|
|
|
Checks that lock with same name already exists. This method returns true, even if
|
|
|
lock have another id.
|
|
|
"""
|
|
|
return self._client.exists(self._name) == 1
|
|
|
|
|
|
|
|
|
reset_all_script = None
|
|
|
|
|
|
|
|
|
def reset_all(redis_client):
|
|
|
"""
|
|
|
Forcibly deletes all locks if its remains (like a crash reason). Use this with care.
|
|
|
|
|
|
:param redis_client:
|
|
|
An instance of :class:`~StrictRedis`.
|
|
|
"""
|
|
|
Lock.register_scripts(redis_client)
|
|
|
|
|
|
reset_all_script(client=redis_client) # noqa
|
|
|
|
