from __future__ import print_function, division, absolute_import from collections import defaultdict import logging import uuid from tornado import gen import tornado.locks try: from cytoolz import merge except ImportError: from toolz import merge from .client import Future, _get_global_client, Client from .metrics import time from .utils import tokey, log_errors from .worker import get_client logger = logging.getLogger(__name__) class VariableExtension(object): """ An extension for the scheduler to manage queues This adds the following routes to the scheduler * variable-set * variable-get * variable-delete """ def __init__(self, scheduler): self.scheduler = scheduler self.variables = dict() self.waiting = defaultdict(set) self.waiting_conditions = defaultdict(tornado.locks.Condition) self.started = tornado.locks.Condition() self.scheduler.handlers.update( {"variable_set": self.set, "variable_get": self.get} ) self.scheduler.stream_handlers["variable-future-release"] = self.future_release self.scheduler.stream_handlers["variable_delete"] = self.delete self.scheduler.extensions["variables"] = self def set(self, stream=None, name=None, key=None, data=None, client=None): if key is not None: record = {"type": "Future", "value": key} self.scheduler.client_desires_keys(keys=[key], client="variable-%s" % name) else: record = {"type": "msgpack", "value": data} try: old = self.variables[name] except KeyError: pass else: if old["type"] == "Future" and old["value"] != key: self.release(old["value"], name) if name not in self.variables: self.started.notify_all() self.variables[name] = record @gen.coroutine def release(self, key, name): while self.waiting[key, name]: yield self.waiting_conditions[name].wait() self.scheduler.client_releases_keys(keys=[key], client="variable-%s" % name) del self.waiting[key, name] def future_release(self, name=None, key=None, token=None, client=None): self.waiting[key, name].remove(token) if not self.waiting[key, name]: self.waiting_conditions[name].notify_all() @gen.coroutine def get(self, stream=None, name=None, client=None, timeout=None): start = time() while name not in self.variables: if timeout is not None: left = timeout - (time() - start) else: left = None if left and left < 0: raise gen.TimeoutError() yield self.started.wait(timeout=left) record = self.variables[name] if record["type"] == "Future": key = record["value"] token = uuid.uuid4().hex ts = self.scheduler.tasks.get(key) state = ts.state if ts is not None else "lost" msg = {"token": token, "state": state} if state == "erred": msg["exception"] = ts.exception_blame.exception msg["traceback"] = ts.exception_blame.traceback record = merge(record, msg) self.waiting[key, name].add(token) raise gen.Return(record) @gen.coroutine def delete(self, stream=None, name=None, client=None): with log_errors(): try: old = self.variables[name] except KeyError: pass else: if old["type"] == "Future": yield self.release(old["value"], name) del self.waiting_conditions[name] del self.variables[name] class Variable(object): """ Distributed Global Variable This allows multiple clients to share futures and data between each other with a single mutable variable. All metadata is sequentialized through the scheduler. Race conditions can occur. Values must be either Futures or msgpack-encodable data (ints, lists, strings, etc..) All data will be kept and sent through the scheduler, so it is wise not to send too much. If you want to share a large amount of data then ``scatter`` it and share the future instead. .. warning:: This object is experimental and has known issues in Python 2 Examples -------- >>> from dask.distributed import Client, Variable # doctest: +SKIP >>> client = Client() # doctest: +SKIP >>> x = Variable('x') # doctest: +SKIP >>> x.set(123) # docttest: +SKIP >>> x.get() # docttest: +SKIP 123 >>> future = client.submit(f, x) # doctest: +SKIP >>> x.set(future) # doctest: +SKIP See Also -------- Queue: shared multi-producer/multi-consumer queue between clients """ def __init__(self, name=None, client=None, maxsize=0): self.client = client or _get_global_client() self.name = name or "variable-" + uuid.uuid4().hex @gen.coroutine def _set(self, value): if isinstance(value, Future): yield self.client.scheduler.variable_set( key=tokey(value.key), name=self.name ) else: yield self.client.scheduler.variable_set(data=value, name=self.name) def set(self, value, **kwargs): """ Set the value of this variable Parameters ---------- value: Future or object Must be either a Future or a msgpack-encodable value """ return self.client.sync(self._set, value, **kwargs) @gen.coroutine def _get(self, timeout=None): d = yield self.client.scheduler.variable_get( timeout=timeout, name=self.name, client=self.client.id ) if d["type"] == "Future": value = Future(d["value"], self.client, inform=True, state=d["state"]) if d["state"] == "erred": value._state.set_error(d["exception"], d["traceback"]) self.client._send_to_scheduler( { "op": "variable-future-release", "name": self.name, "key": d["value"], "token": d["token"], } ) else: value = d["value"] raise gen.Return(value) def get(self, timeout=None, **kwargs): """ Get the value of this variable """ return self.client.sync(self._get, timeout=timeout, **kwargs) def delete(self): """ Delete this variable Caution, this affects all clients currently pointing to this variable. """ if self.client.status == "running": # TODO: can leave zombie futures self.client._send_to_scheduler({"op": "variable_delete", "name": self.name}) def __getstate__(self): return (self.name, self.client.scheduler.address) def __setstate__(self, state): name, address = state try: client = get_client(address) assert client.scheduler.address == address except (AttributeError, AssertionError): client = Client(address, set_as_default=False) self.__init__(name=name, client=client)