feat(locks): added no-blocking option for redis blocks

rhodecode/lib/_vendor/redis_lock/__init__.py

@@ -1,394 +1,402 b''
 
 import threading
 import weakref
 from base64 import b64encode
 from logging import getLogger
 from os import urandom
 from typing import Union
 
 from redis import StrictRedis
 
 __version__ = '4.0.0'
 
 loggers = {
     k: getLogger("rhodecode." + ".".join((__name__, k)))
     for k in [
         "acquire",
         "refresh.thread.start",
         "refresh.thread.stop",
         "refresh.thread.exit",
         "refresh.start",
         "refresh.shutdown",
         "refresh.exit",
         "release",
     ]
 }
 
 text_type = str
 binary_type = bytes
 
 
 # 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
+    blocking = None
 
     _lock_renewal_interval: float
     _lock_renewal_thread: Union[threading.Thread, None]
 
-    def __init__(self, redis_client, name, expire=None, id=None, auto_renewal=False, strict=True, signal_expire=1000):
+    def __init__(self, redis_client, name, expire=None, id=None, auto_renewal=False, strict=True, signal_expire=1000, blocking=True):
         """
         :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``.
+        :param blocking:
+            Boolean value specifying whether lock should be blocking or not.
+            Used in `__enter__` method.
         """
         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(f"Incorrect type for `id`. Must be bytes/str not {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.blocking = blocking
+
         self.register_scripts(redis_client)
 
     @classmethod
     def register_scripts(cls, redis_client):
         global reset_all_script
         if reset_all_script is None:
             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)
             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(f"Timeout ({timeout}) cannot be less than or equal to 0")
 
             if self._expire and not self._lock_renewal_interval and timeout > self._expire:
                 raise TimeoutTooLarge(f"Timeout ({timeout}) cannot be greater than expire ({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 acquire Lock(%r).", self._name)
                     return False
 
         logger.debug("Acquired Lock(%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(f"Lock {self._name} is not acquired or it already expired.")
         elif error == 2:
             raise NotExpirable(f"Lock {self._name} has no assigned expiration time")
         elif error:
             raise RuntimeError(f"Unsupported error code {error} from EXTEND script")
 
     @staticmethod
     def _lock_renewer(name, 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(%r).", name)
             lock: "Lock" = lockref()
             if lock is None:
                 loggers["refresh.thread.stop"].debug(
                     "Stopping loop because Lock(%r) was garbage collected.", name
                 )
                 break
             lock.extend(expire=lock._expire)
             del lock
         loggers["refresh.thread.exit"].debug("Exiting renewal thread for Lock(%r).", name)
 
     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 renewal thread for Lock(%r). Refresh interval: %s seconds.",
             self._name, self._lock_renewal_interval
         )
         self._lock_renewal_stop = threading.Event()
         self._lock_renewal_thread = threading.Thread(
             group=None,
             target=self._lock_renewer,
             kwargs={
                 'name': self._name,
                 'lockref': weakref.ref(self),
                 'interval': self._lock_renewal_interval,
                 'stop': self._lock_renewal_stop,
             },
         )
         self._lock_renewal_thread.daemon = 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("Signaling renewal thread for Lock(%r) to exit.", self._name)
         self._lock_renewal_stop.set()
         self._lock_renewal_thread.join()
         self._lock_renewal_thread = None
         loggers["refresh.exit"].debug("Renewal thread for Lock(%r) exited.", self._name)
 
     def __enter__(self):
-        acquired = self.acquire(blocking=True)
+        acquired = self.acquire(blocking=self.blocking)
         if not acquired:
+            if self.blocking:
             raise AssertionError(f"Lock({self._name}) wasn't acquired, but blocking=True was used!")
+            raise NotAcquired(f"Lock({self._name}) is not acquired or it already expired.")
         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 Lock(%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(f"Lock({self._name}) is not acquired or it already expired.")
         elif error:
             raise RuntimeError(f"Unsupported error code {error} from EXTEND script.")
 
     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