Source code for distributed.lock

from __future__ import annotations

import asyncio
import logging
import uuid
from collections import defaultdict, deque

from dask.utils import parse_timedelta

from distributed.utils import TimeoutError, log_errors, wait_for
from distributed.worker import get_client

logger = logging.getLogger(__name__)

class LockExtension:
    """An extension for the scheduler to manage Locks

    This adds the following routes to the scheduler

    *  lock_acquire
    *  lock_release

    def __init__(self, scheduler):
        self.scheduler = scheduler = defaultdict(deque)
        self.ids = dict()

            {"lock_acquire": self.acquire, "lock_release": self.release}

    async def acquire(self, name=None, id=None, timeout=None):
        if isinstance(name, list):
            name = tuple(name)
        if name not in self.ids:
            result = True
            while name in self.ids:
                event = asyncio.Event()
                future = event.wait()
                if timeout is not None:
                    future = wait_for(future, timeout)
                    await future
                except TimeoutError:
                    result = False
                    result = True
                    event2 =[name].popleft()
                    assert event is event2
        if result:
            assert name not in self.ids
            self.ids[name] = id
        return result

    def release(self, name=None, id=None):
        if isinstance(name, list):
            name = tuple(name)
        if self.ids.get(name) != id:
            raise ValueError("This lock has not yet been acquired")
        del self.ids[name]

[docs]class Lock: """Distributed Centralized Lock Parameters ---------- name: string (optional) Name of the lock to acquire. Choosing the same name allows two disconnected processes to coordinate a lock. If not given, a random name will be generated. client: Client (optional) Client to use for communication with the scheduler. If not given, the default global client will be used. Examples -------- >>> lock = Lock('x') # doctest: +SKIP >>> lock.acquire(timeout=1) # doctest: +SKIP >>> # do things with protected resource >>> lock.release() # doctest: +SKIP """ def __init__(self, name=None, client=None): self._client = client = name or "lock-" + uuid.uuid4().hex = uuid.uuid4().hex self._locked = False @property def client(self): if not self._client: try: self._client = get_client() except ValueError: pass return self._client def _verify_running(self): if not self.client: raise RuntimeError( f"{type(self)} object not properly initialized. This can happen" " if the object is being deserialized outside of the context of" " a Client or Worker." )
[docs] def acquire(self, blocking=True, timeout=None): """Acquire the lock Parameters ---------- blocking : bool, optional If false, don't wait on the lock in the scheduler at all. timeout : string or number or timedelta, optional Seconds to wait on the lock in the scheduler. This does not include local coroutine time, network transfer time, etc.. It is forbidden to specify a timeout when blocking is false. Instead of number of seconds, it is also possible to specify a timedelta in string format, e.g. "200ms". Examples -------- >>> lock = Lock('x') # doctest: +SKIP >>> lock.acquire(timeout="1s") # doctest: +SKIP Returns ------- True or False whether or not it successfully acquired the lock """ self._verify_running() timeout = parse_timedelta(timeout) if not blocking: if timeout is not None: raise ValueError("can't specify a timeout for a non-blocking call") timeout = 0 result = self.client.sync( self.client.scheduler.lock_acquire,,, timeout=timeout, ) self._locked = True return result
[docs] def release(self): """Release the lock if already acquired""" self._verify_running() if not self.locked(): raise ValueError("Lock is not yet acquired") result = self.client.sync( self.client.scheduler.lock_release,, ) self._locked = False return result
def locked(self): return self._locked def __enter__(self): self.acquire() return self def __exit__(self, exc_type, exc_value, traceback): self.release() async def __aenter__(self): await self.acquire() return self async def __aexit__(self, exc_type, exc_value, traceback): await self.release() def __reduce__(self): return (Lock, (,))