This document describes the current stable version of Celery (3.1). For development docs, go here.

Source code for celery.result

# -*- coding: utf-8 -*-
"""
    celery.result
    ~~~~~~~~~~~~~

    Task results/state and groups of results.

"""
from __future__ import absolute_import

import time
import warnings

from collections import deque
from contextlib import contextmanager
from copy import copy

from kombu.utils import cached_property
from kombu.utils.compat import OrderedDict

from . import current_app
from . import states
from ._state import _set_task_join_will_block, task_join_will_block
from .app import app_or_default
from .datastructures import DependencyGraph, GraphFormatter
from .exceptions import IncompleteStream, TimeoutError
from .five import items, range, string_t, monotonic
from .utils import deprecated

__all__ = ['ResultBase', 'AsyncResult', 'ResultSet', 'GroupResult',
           'EagerResult', 'result_from_tuple']

E_WOULDBLOCK = """\
Never call result.get() within a task!
See http://docs.celeryq.org/en/latest/userguide/tasks.html\
#task-synchronous-subtasks

In Celery 3.2 this will result in an exception being
raised instead of just being a warning.
"""


def assert_will_not_block():
    if task_join_will_block():
        warnings.warn(RuntimeWarning(E_WOULDBLOCK))


@contextmanager
def allow_join_result():
    reset_value = task_join_will_block()
    _set_task_join_will_block(False)
    try:
        yield
    finally:
        _set_task_join_will_block(reset_value)


[docs]class ResultBase(object): """Base class for all results""" #: Parent result (if part of a chain) parent = None
[docs]class AsyncResult(ResultBase): """Query task state. :param id: see :attr:`id`. :keyword backend: see :attr:`backend`. """ app = None #: Error raised for timeouts. TimeoutError = TimeoutError #: The task's UUID. id = None #: The task result backend to use. backend = None def __init__(self, id, backend=None, task_name=None, app=None, parent=None): self.app = app_or_default(app or self.app) self.id = id self.backend = backend or self.app.backend self.task_name = task_name self.parent = parent self._cache = None
[docs] def as_tuple(self): parent = self.parent return (self.id, parent and parent.as_tuple()), None
serializable = as_tuple # XXX compat
[docs] def forget(self): """Forget about (and possibly remove the result of) this task.""" self._cache = None self.backend.forget(self.id)
[docs] def revoke(self, connection=None, terminate=False, signal=None, wait=False, timeout=None): """Send revoke signal to all workers. Any worker receiving the task, or having reserved the task, *must* ignore it. :keyword terminate: Also terminate the process currently working on the task (if any). :keyword signal: Name of signal to send to process if terminate. Default is TERM. :keyword wait: Wait for replies from workers. Will wait for 1 second by default or you can specify a custom ``timeout``. :keyword timeout: Time in seconds to wait for replies if ``wait`` enabled. """ self.app.control.revoke(self.id, connection=connection, terminate=terminate, signal=signal, reply=wait, timeout=timeout)
[docs] def get(self, timeout=None, propagate=True, interval=0.5, no_ack=True, follow_parents=True): """Wait until task is ready, and return its result. .. warning:: Waiting for tasks within a task may lead to deadlocks. Please read :ref:`task-synchronous-subtasks`. :keyword timeout: How long to wait, in seconds, before the operation times out. :keyword propagate: Re-raise exception if the task failed. :keyword interval: Time to wait (in seconds) before retrying to retrieve the result. Note that this does not have any effect when using the amqp result store backend, as it does not use polling. :keyword no_ack: Enable amqp no ack (automatically acknowledge message). If this is :const:`False` then the message will **not be acked**. :keyword follow_parents: Reraise any exception raised by parent task. :raises celery.exceptions.TimeoutError: if `timeout` is not :const:`None` and the result does not arrive within `timeout` seconds. If the remote call raised an exception then that exception will be re-raised. """ assert_will_not_block() on_interval = None if follow_parents and propagate and self.parent: on_interval = self._maybe_reraise_parent_error on_interval() if self._cache: if propagate: self.maybe_reraise() return self.result try: return self.backend.wait_for( self.id, timeout=timeout, propagate=propagate, interval=interval, on_interval=on_interval, no_ack=no_ack, ) finally: self._get_task_meta() # update self._cache
wait = get # deprecated alias to :meth:`get`. def _maybe_reraise_parent_error(self): for node in reversed(list(self._parents())): node.maybe_reraise() def _parents(self): node = self.parent while node: yield node node = node.parent
[docs] def collect(self, intermediate=False, **kwargs): """Iterator, like :meth:`get` will wait for the task to complete, but will also follow :class:`AsyncResult` and :class:`ResultSet` returned by the task, yielding ``(result, value)`` tuples for each result in the tree. An example would be having the following tasks: .. code-block:: python from celery import group from proj.celery import app @app.task(trail=True) def A(how_many): return group(B.s(i) for i in range(how_many))() @app.task(trail=True) def B(i): return pow2.delay(i) @app.task(trail=True) def pow2(i): return i ** 2 Note that the ``trail`` option must be enabled so that the list of children is stored in ``result.children``. This is the default but enabled explicitly for illustration. Calling :meth:`collect` would return: .. code-block:: python >>> from celery.result import ResultBase >>> from proj.tasks import A >>> result = A.delay(10) >>> [v for v in result.collect() ... if not isinstance(v, (ResultBase, tuple))] [0, 1, 4, 9, 16, 25, 36, 49, 64, 81] """ for _, R in self.iterdeps(intermediate=intermediate): yield R, R.get(**kwargs)
[docs] def get_leaf(self): value = None for _, R in self.iterdeps(): value = R.get() return value
[docs] def iterdeps(self, intermediate=False): stack = deque([(None, self)]) while stack: parent, node = stack.popleft() yield parent, node if node.ready(): stack.extend((node, child) for child in node.children or []) else: if not intermediate: raise IncompleteStream()
[docs] def ready(self): """Returns :const:`True` if the task has been executed. If the task is still running, pending, or is waiting for retry then :const:`False` is returned. """ return self.state in self.backend.READY_STATES
[docs] def successful(self): """Returns :const:`True` if the task executed successfully.""" return self.state == states.SUCCESS
[docs] def failed(self): """Returns :const:`True` if the task failed.""" return self.state == states.FAILURE
[docs] def maybe_reraise(self): if self.state in states.PROPAGATE_STATES: raise self.result
[docs] def build_graph(self, intermediate=False, formatter=None): graph = DependencyGraph( formatter=formatter or GraphFormatter(root=self.id, shape='oval'), ) for parent, node in self.iterdeps(intermediate=intermediate): graph.add_arc(node) if parent: graph.add_edge(parent, node) return graph
def __str__(self): """`str(self) -> self.id`""" return str(self.id) def __hash__(self): """`hash(self) -> hash(self.id)`""" return hash(self.id) def __repr__(self): return '<{0}: {1}>'.format(type(self).__name__, self.id) def __eq__(self, other): if isinstance(other, AsyncResult): return other.id == self.id elif isinstance(other, string_t): return other == self.id return NotImplemented def __ne__(self, other): return not self.__eq__(other) def __copy__(self): return self.__class__( self.id, self.backend, self.task_name, self.app, self.parent, ) def __reduce__(self): return self.__class__, self.__reduce_args__() def __reduce_args__(self): return self.id, self.backend, self.task_name, None, self.parent def __del__(self): self._cache = None @cached_property
[docs] def graph(self): return self.build_graph()
@property
[docs] def supports_native_join(self): return self.backend.supports_native_join
@property
[docs] def children(self): return self._get_task_meta().get('children')
def _get_task_meta(self): if self._cache is None: meta = self.backend.get_task_meta(self.id) if meta: state = meta['status'] if state == states.SUCCESS or state in states.PROPAGATE_STATES: return self._set_cache(meta) return meta return self._cache def _set_cache(self, d): state, children = d['status'], d.get('children') if state in states.EXCEPTION_STATES: d['result'] = self.backend.exception_to_python(d['result']) if children: d['children'] = [ result_from_tuple(child, self.app) for child in children ] self._cache = d return d @property
[docs] def result(self): """When the task has been executed, this contains the return value. If the task raised an exception, this will be the exception instance.""" return self._get_task_meta()['result']
info = result @property
[docs] def traceback(self): """Get the traceback of a failed task.""" return self._get_task_meta().get('traceback')
@property
[docs] def state(self): """The tasks current state. Possible values includes: *PENDING* The task is waiting for execution. *STARTED* The task has been started. *RETRY* The task is to be retried, possibly because of failure. *FAILURE* The task raised an exception, or has exceeded the retry limit. The :attr:`result` attribute then contains the exception raised by the task. *SUCCESS* The task executed successfully. The :attr:`result` attribute then contains the tasks return value. """ return self._get_task_meta()['status']
status = state @property def task_id(self): """compat alias to :attr:`id`""" return self.id @task_id.setter # noqa
[docs] def task_id(self, id): self.id = id
BaseAsyncResult = AsyncResult # for backwards compatibility.
[docs]class ResultSet(ResultBase): """Working with more than one result. :param results: List of result instances. """ app = None #: List of results in in the set. results = None def __init__(self, results, app=None, **kwargs): self.app = app_or_default(app or self.app) self.results = results
[docs] def add(self, result): """Add :class:`AsyncResult` as a new member of the set. Does nothing if the result is already a member. """ if result not in self.results: self.results.append(result)
[docs] def remove(self, result): """Remove result from the set; it must be a member. :raises KeyError: if the result is not a member. """ if isinstance(result, string_t): result = self.app.AsyncResult(result) try: self.results.remove(result) except ValueError: raise KeyError(result)
[docs] def discard(self, result): """Remove result from the set if it is a member. If it is not a member, do nothing. """ try: self.remove(result) except KeyError: pass
[docs] def update(self, results): """Update set with the union of itself and an iterable with results.""" self.results.extend(r for r in results if r not in self.results)
[docs] def clear(self): """Remove all results from this set.""" self.results[:] = [] # don't create new list.
[docs] def successful(self): """Was all of the tasks successful? :returns: :const:`True` if all of the tasks finished successfully (i.e. did not raise an exception). """ return all(result.successful() for result in self.results)
[docs] def failed(self): """Did any of the tasks fail? :returns: :const:`True` if one of the tasks failed. (i.e., raised an exception) """ return any(result.failed() for result in self.results)
[docs] def maybe_reraise(self): for result in self.results: result.maybe_reraise()
[docs] def waiting(self): """Are any of the tasks incomplete? :returns: :const:`True` if one of the tasks are still waiting for execution. """ return any(not result.ready() for result in self.results)
[docs] def ready(self): """Did all of the tasks complete? (either by success of failure). :returns: :const:`True` if all of the tasks has been executed. """ return all(result.ready() for result in self.results)
[docs] def completed_count(self): """Task completion count. :returns: the number of tasks completed. """ return sum(int(result.successful()) for result in self.results)
[docs] def forget(self): """Forget about (and possible remove the result of) all the tasks.""" for result in self.results: result.forget()
[docs] def revoke(self, connection=None, terminate=False, signal=None, wait=False, timeout=None): """Send revoke signal to all workers for all tasks in the set. :keyword terminate: Also terminate the process currently working on the task (if any). :keyword signal: Name of signal to send to process if terminate. Default is TERM. :keyword wait: Wait for replies from worker. Will wait for 1 second by default or you can specify a custom ``timeout``. :keyword timeout: Time in seconds to wait for replies if ``wait`` enabled. """ self.app.control.revoke([r.id for r in self.results], connection=connection, timeout=timeout, terminate=terminate, signal=signal, reply=wait)
def __iter__(self): return iter(self.results) def __getitem__(self, index): """`res[i] -> res.results[i]`""" return self.results[index] @deprecated('3.2', '3.3')
[docs] def iterate(self, timeout=None, propagate=True, interval=0.5): """Deprecated method, use :meth:`get` with a callback argument.""" elapsed = 0.0 results = OrderedDict((result.id, copy(result)) for result in self.results) while results: removed = set() for task_id, result in items(results): if result.ready(): yield result.get(timeout=timeout and timeout - elapsed, propagate=propagate) removed.add(task_id) else: if result.backend.subpolling_interval: time.sleep(result.backend.subpolling_interval) for task_id in removed: results.pop(task_id, None) time.sleep(interval) elapsed += interval if timeout and elapsed >= timeout: raise TimeoutError('The operation timed out')
[docs] def get(self, timeout=None, propagate=True, interval=0.5, callback=None, no_ack=True): """See :meth:`join` This is here for API compatibility with :class:`AsyncResult`, in addition it uses :meth:`join_native` if available for the current result backend. """ return (self.join_native if self.supports_native_join else self.join)( timeout=timeout, propagate=propagate, interval=interval, callback=callback, no_ack=no_ack)
[docs] def join(self, timeout=None, propagate=True, interval=0.5, callback=None, no_ack=True): """Gathers the results of all tasks as a list in order. .. note:: This can be an expensive operation for result store backends that must resort to polling (e.g. database). You should consider using :meth:`join_native` if your backend supports it. .. warning:: Waiting for tasks within a task may lead to deadlocks. Please see :ref:`task-synchronous-subtasks`. :keyword timeout: The number of seconds to wait for results before the operation times out. :keyword propagate: If any of the tasks raises an exception, the exception will be re-raised. :keyword interval: Time to wait (in seconds) before retrying to retrieve a result from the set. Note that this does not have any effect when using the amqp result store backend, as it does not use polling. :keyword callback: Optional callback to be called for every result received. Must have signature ``(task_id, value)`` No results will be returned by this function if a callback is specified. The order of results is also arbitrary when a callback is used. To get access to the result object for a particular id you will have to generate an index first: ``index = {r.id: r for r in gres.results.values()}`` Or you can create new result objects on the fly: ``result = app.AsyncResult(task_id)`` (both will take advantage of the backend cache anyway). :keyword no_ack: Automatic message acknowledgement (Note that if this is set to :const:`False` then the messages *will not be acknowledged*). :raises celery.exceptions.TimeoutError: if ``timeout`` is not :const:`None` and the operation takes longer than ``timeout`` seconds. """ assert_will_not_block() time_start = monotonic() remaining = None results = [] for result in self.results: remaining = None if timeout: remaining = timeout - (monotonic() - time_start) if remaining <= 0.0: raise TimeoutError('join operation timed out') value = result.get( timeout=remaining, propagate=propagate, interval=interval, no_ack=no_ack, ) if callback: callback(result.id, value) else: results.append(value) return results
[docs] def iter_native(self, timeout=None, interval=0.5, no_ack=True): """Backend optimized version of :meth:`iterate`. .. versionadded:: 2.2 Note that this does not support collecting the results for different task types using different backends. This is currently only supported by the amqp, Redis and cache result backends. """ results = self.results if not results: return iter([]) return self.backend.get_many( set(r.id for r in results), timeout=timeout, interval=interval, no_ack=no_ack, )
[docs] def join_native(self, timeout=None, propagate=True, interval=0.5, callback=None, no_ack=True): """Backend optimized version of :meth:`join`. .. versionadded:: 2.2 Note that this does not support collecting the results for different task types using different backends. This is currently only supported by the amqp, Redis and cache result backends. """ assert_will_not_block() order_index = None if callback else dict( (result.id, i) for i, result in enumerate(self.results) ) acc = None if callback else [None for _ in range(len(self))] for task_id, meta in self.iter_native(timeout, interval, no_ack): value = meta['result'] if propagate and meta['status'] in states.PROPAGATE_STATES: raise value if callback: callback(task_id, value) else: acc[order_index[task_id]] = value return acc
def _failed_join_report(self): return (res for res in self.results if res.backend.is_cached(res.id) and res.state in states.PROPAGATE_STATES) def __len__(self): return len(self.results) def __eq__(self, other): if isinstance(other, ResultSet): return other.results == self.results return NotImplemented def __ne__(self, other): return not self.__eq__(other) def __repr__(self): return '<{0}: [{1}]>'.format(type(self).__name__, ', '.join(r.id for r in self.results)) @property
[docs] def subtasks(self): """Deprecated alias to :attr:`results`.""" return self.results
@property
[docs] def supports_native_join(self): try: return self.results[0].supports_native_join except IndexError: pass
@property
[docs] def backend(self): return self.app.backend if self.app else self.results[0].backend
[docs]class GroupResult(ResultSet): """Like :class:`ResultSet`, but with an associated id. This type is returned by :class:`~celery.group`, and the deprecated TaskSet, meth:`~celery.task.TaskSet.apply_async` method. It enables inspection of the tasks state and return values as a single entity. :param id: The id of the group. :param results: List of result instances. """ #: The UUID of the group. id = None #: List/iterator of results in the group results = None def __init__(self, id=None, results=None, **kwargs): self.id = id ResultSet.__init__(self, results, **kwargs)
[docs] def save(self, backend=None): """Save group-result for later retrieval using :meth:`restore`. Example:: >>> def save_and_restore(result): ... result.save() ... result = GroupResult.restore(result.id) """ return (backend or self.app.backend).save_group(self.id, self)
[docs] def delete(self, backend=None): """Remove this result if it was previously saved.""" (backend or self.app.backend).delete_group(self.id)
def __reduce__(self): return self.__class__, self.__reduce_args__() def __reduce_args__(self): return self.id, self.results def __eq__(self, other): if isinstance(other, GroupResult): return other.id == self.id and other.results == self.results return NotImplemented def __ne__(self, other): return not self.__eq__(other) def __repr__(self): return '<{0}: {1} [{2}]>'.format(type(self).__name__, self.id, ', '.join(r.id for r in self.results))
[docs] def as_tuple(self): return self.id, [r.as_tuple() for r in self.results]
serializable = as_tuple # XXX compat @property
[docs] def children(self): return self.results
@classmethod
[docs] def restore(self, id, backend=None): """Restore previously saved group result.""" return ( backend or (self.app.backend if self.app else current_app.backend) ).restore_group(id)
class TaskSetResult(GroupResult): """Deprecated version of :class:`GroupResult`""" def __init__(self, taskset_id, results=None, **kwargs): # XXX supports the taskset_id kwarg. # XXX previously the "results" arg was named "subtasks". if 'subtasks' in kwargs: results = kwargs['subtasks'] GroupResult.__init__(self, taskset_id, results, **kwargs) def itersubtasks(self): """Deprecated. Use ``iter(self.results)`` instead.""" return iter(self.results) @property def total(self): """Deprecated: Use ``len(r)``.""" return len(self) @property def taskset_id(self): """compat alias to :attr:`self.id`""" return self.id @taskset_id.setter # noqa def taskset_id(self, id): self.id = id
[docs]class EagerResult(AsyncResult): """Result that we know has already been executed.""" task_name = None def __init__(self, id, ret_value, state, traceback=None): self.id = id self._result = ret_value self._state = state self._traceback = traceback def _get_task_meta(self): return {'task_id': self.id, 'result': self._result, 'status': self._state, 'traceback': self._traceback} def __reduce__(self): return self.__class__, self.__reduce_args__() def __reduce_args__(self): return (self.id, self._result, self._state, self._traceback) def __copy__(self): cls, args = self.__reduce__() return cls(*args)
[docs] def ready(self): return True
[docs] def get(self, timeout=None, propagate=True, **kwargs): if self.successful(): return self.result elif self.state in states.PROPAGATE_STATES: if propagate: raise self.result return self.result
wait = get
[docs] def forget(self): pass
[docs] def revoke(self, *args, **kwargs): self._state = states.REVOKED
def __repr__(self): return '<EagerResult: {0.id}>'.format(self) @property
[docs] def result(self): """The tasks return value""" return self._result
@property
[docs] def state(self): """The tasks state.""" return self._state
status = state @property
[docs] def traceback(self): """The traceback if the task failed.""" return self._traceback
@property
[docs] def supports_native_join(self): return False
[docs]def result_from_tuple(r, app=None): # earlier backends may just pickle, so check if # result is already prepared. app = app_or_default(app) Result = app.AsyncResult if not isinstance(r, ResultBase): res, nodes = r if nodes: return app.GroupResult( res, [result_from_tuple(child, app) for child in nodes], ) # previously did not include parent id, parent = res if isinstance(res, (list, tuple)) else (res, None) if parent: parent = result_from_tuple(parent, app) return Result(id, parent=parent) return r
from_serializable = result_from_tuple # XXX compat