This document describes Celery 3.1. For development docs, go here.
# -*- coding: utf-8 -*-
"""
celery.events.state
~~~~~~~~~~~~~~~~~~~
This module implements a datastructure used to keep
track of the state of a cluster of workers and the tasks
it is working on (by consuming events).
For every event consumed the state is updated,
so the state represents the state of the cluster
at the time of the last event.
Snapshots (:mod:`celery.events.snapshot`) can be used to
take "pictures" of this state at regular intervals
to e.g. store that in a database.
"""
from __future__ import absolute_import
import sys
import threading
from datetime import datetime
from heapq import heappush, heappop
from itertools import islice
from time import time
from kombu.clocks import timetuple
from kombu.utils import kwdict
from celery import states
from celery.datastructures import AttributeDict
from celery.five import items, values
from celery.utils.functional import LRUCache
from celery.utils.log import get_logger
# The window (in percentage) is added to the workers heartbeat
# frequency. If the time between updates exceeds this window,
# then the worker is considered to be offline.
HEARTBEAT_EXPIRE_WINDOW = 200
# Max drift between event timestamp and time of event received
# before we alert that clocks may be unsynchronized.
HEARTBEAT_DRIFT_MAX = 16
DRIFT_WARNING = """\
Substantial drift from %s may mean clocks are out of sync. Current drift is
%s seconds. [orig: %s recv: %s]
"""
CAN_KWDICT = sys.version_info >= (2, 6, 5)
logger = get_logger(__name__)
warn = logger.warning
R_STATE = '<State: events={0.event_count} tasks={0.task_count}>'
R_WORKER = '<Worker: {0.hostname} ({0.status_string})'
R_TASK = '<Task: {0.name}({0.uuid}) {0.state}>'
__all__ = ['Worker', 'Task', 'State', 'heartbeat_expires']
[docs]def heartbeat_expires(timestamp, freq=60,
expire_window=HEARTBEAT_EXPIRE_WINDOW):
return timestamp + freq * (expire_window / 1e2)
def with_unique_field(attr):
def _decorate_cls(cls):
def __eq__(this, other):
if isinstance(other, this.__class__):
return getattr(this, attr) == getattr(other, attr)
return NotImplemented
cls.__eq__ = __eq__
def __ne__(this, other):
return not this.__eq__(other)
cls.__ne__ = __ne__
def __hash__(this):
return hash(getattr(this, attr))
cls.__hash__ = __hash__
return cls
return _decorate_cls
@with_unique_field('hostname')
[docs]class Worker(AttributeDict):
"""Worker State."""
heartbeat_max = 4
expire_window = HEARTBEAT_EXPIRE_WINDOW
pid = None
_defaults = {'hostname': None, 'pid': None, 'freq': 60}
def __init__(self, **fields):
dict.__init__(self, self._defaults, **fields)
self.heartbeats = []
[docs] def on_online(self, timestamp=None, local_received=None, **kwargs):
"""Callback for the :event:`worker-online` event."""
self.update(**kwargs)
self.update_heartbeat(local_received, timestamp)
[docs] def on_offline(self, **kwargs):
"""Callback for the :event:`worker-offline` event."""
self.update(**kwargs)
self.heartbeats = []
[docs] def on_heartbeat(self, timestamp=None, local_received=None, **kwargs):
"""Callback for the :event:`worker-heartbeat` event."""
self.update(**kwargs)
self.update_heartbeat(local_received, timestamp)
[docs] def update_heartbeat(self, received, timestamp):
if not received or not timestamp:
return
drift = abs(int(received) - int(timestamp))
if drift > HEARTBEAT_DRIFT_MAX:
warn(DRIFT_WARNING, self.hostname, drift,
datetime.fromtimestamp(received),
datetime.fromtimestamp(timestamp))
heartbeats, hbmax = self.heartbeats, self.heartbeat_max
if not heartbeats or (received and received > heartbeats[-1]):
heappush(heartbeats, received)
if len(heartbeats) > hbmax:
heartbeats[:] = heartbeats[hbmax:]
def __repr__(self):
return R_WORKER.format(self)
@property
@property
[docs] def heartbeat_expires(self):
return heartbeat_expires(self.heartbeats[-1],
self.freq, self.expire_window)
@property
@property
@with_unique_field('uuid')
[docs]class Task(AttributeDict):
"""Task State."""
#: How to merge out of order events.
#: Disorder is detected by logical ordering (e.g. :event:`task-received`
#: must have happened before a :event:`task-failed` event).
#:
#: A merge rule consists of a state and a list of fields to keep from
#: that state. ``(RECEIVED, ('name', 'args')``, means the name and args
#: fields are always taken from the RECEIVED state, and any values for
#: these fields received before or after is simply ignored.
merge_rules = {states.RECEIVED: ('name', 'args', 'kwargs',
'retries', 'eta', 'expires')}
#: meth:`info` displays these fields by default.
_info_fields = ('args', 'kwargs', 'retries', 'result',
'eta', 'runtime', 'expires', 'exception',
'exchange', 'routing_key')
#: Default values.
_defaults = dict(uuid=None, name=None, state=states.PENDING,
received=False, sent=False, started=False,
succeeded=False, failed=False, retried=False,
revoked=False, args=None, kwargs=None, eta=None,
expires=None, retries=None, worker=None, result=None,
exception=None, timestamp=None, runtime=None,
traceback=None, exchange=None, routing_key=None,
clock=0)
def __init__(self, **fields):
dict.__init__(self, self._defaults, **fields)
[docs] def update(self, state, timestamp, fields, _state=states.state):
"""Update state from new event.
:param state: State from event.
:param timestamp: Timestamp from event.
:param fields: Event data.
"""
time_received = fields.get('local_received') or 0
if self.worker and time_received:
self.worker.update_heartbeat(time_received, timestamp)
if state != states.RETRY and self.state != states.RETRY and \
_state(state) < _state(self.state):
# this state logically happens-before the current state, so merge.
self.merge(state, timestamp, fields)
else:
self.state = state
self.timestamp = timestamp
super(Task, self).update(fields)
[docs] def merge(self, state, timestamp, fields):
"""Merge with out of order event."""
keep = self.merge_rules.get(state)
if keep is not None:
fields = dict((key, fields.get(key)) for key in keep)
super(Task, self).update(fields)
[docs] def on_sent(self, timestamp=None, **fields):
"""Callback for the :event:`task-sent` event."""
self.sent = timestamp
self.update(states.PENDING, timestamp, fields)
[docs] def on_received(self, timestamp=None, **fields):
"""Callback for the :event:`task-received` event."""
self.received = timestamp
self.update(states.RECEIVED, timestamp, fields)
[docs] def on_started(self, timestamp=None, **fields):
"""Callback for the :event:`task-started` event."""
self.started = timestamp
self.update(states.STARTED, timestamp, fields)
[docs] def on_failed(self, timestamp=None, **fields):
"""Callback for the :event:`task-failed` event."""
self.failed = timestamp
self.update(states.FAILURE, timestamp, fields)
[docs] def on_retried(self, timestamp=None, **fields):
"""Callback for the :event:`task-retried` event."""
self.retried = timestamp
self.update(states.RETRY, timestamp, fields)
[docs] def on_succeeded(self, timestamp=None, **fields):
"""Callback for the :event:`task-succeeded` event."""
self.succeeded = timestamp
self.update(states.SUCCESS, timestamp, fields)
[docs] def on_revoked(self, timestamp=None, **fields):
"""Callback for the :event:`task-revoked` event."""
self.revoked = timestamp
self.update(states.REVOKED, timestamp, fields)
[docs] def on_unknown_event(self, shortype, timestamp=None, **fields):
self.update(shortype.upper(), timestamp, fields)
[docs] def info(self, fields=None, extra=[]):
"""Information about this task suitable for on-screen display."""
fields = self._info_fields if fields is None else fields
def _keys():
for key in list(fields) + list(extra):
value = getattr(self, key, None)
if value is not None:
yield key, value
return dict(_keys())
def __repr__(self):
return R_TASK.format(self)
@property
[docs]class State(object):
"""Records clusters state."""
event_count = 0
task_count = 0
def __init__(self, callback=None,
workers=None, tasks=None, taskheap=None,
max_workers_in_memory=5000, max_tasks_in_memory=10000):
self.event_callback = callback
self.workers = (LRUCache(max_workers_in_memory)
if workers is None else workers)
self.tasks = (LRUCache(max_tasks_in_memory)
if tasks is None else tasks)
self._taskheap = [] if taskheap is None else taskheap
self.max_workers_in_memory = max_workers_in_memory
self.max_tasks_in_memory = max_tasks_in_memory
self._mutex = threading.Lock()
self.handlers = {'task': self.task_event,
'worker': self.worker_event}
self._get_handler = self.handlers.__getitem__
[docs] def freeze_while(self, fun, *args, **kwargs):
clear_after = kwargs.pop('clear_after', False)
with self._mutex:
try:
return fun(*args, **kwargs)
finally:
if clear_after:
self._clear()
def _clear_tasks(self, ready=True):
if ready:
in_progress = dict(
(uuid, task) for uuid, task in self.itertasks()
if task.state not in states.READY_STATES)
self.tasks.clear()
self.tasks.update(in_progress)
else:
self.tasks.clear()
self._taskheap[:] = []
def _clear(self, ready=True):
self.workers.clear()
self._clear_tasks(ready)
self.event_count = 0
self.task_count = 0
[docs] def get_or_create_worker(self, hostname, **kwargs):
"""Get or create worker by hostname.
Return tuple of ``(worker, was_created)``.
"""
try:
worker = self.workers[hostname]
worker.update(kwargs)
return worker, False
except KeyError:
worker = self.workers[hostname] = Worker(
hostname=hostname, **kwargs)
return worker, True
[docs] def get_or_create_task(self, uuid):
"""Get or create task by uuid."""
try:
return self.tasks[uuid], False
except KeyError:
task = self.tasks[uuid] = Task(uuid=uuid)
return task, True
[docs] def worker_event(self, type, fields):
"""Process worker event."""
try:
hostname = fields['hostname']
except KeyError:
pass
else:
worker, created = self.get_or_create_worker(hostname)
handler = getattr(worker, 'on_' + type, None)
if handler:
handler(**(fields if CAN_KWDICT else kwdict(fields)))
return worker, created
[docs] def task_event(self, type, fields, timetuple=timetuple):
"""Process task event."""
uuid = fields['uuid']
hostname = fields['hostname']
worker, _ = self.get_or_create_worker(hostname)
task, created = self.get_or_create_task(uuid)
task.worker = worker
maxtasks = self.max_tasks_in_memory * 2
taskheap = self._taskheap
timestamp = fields.get('timestamp') or 0
clock = 0 if type == 'sent' else fields.get('clock')
heappush(taskheap, timetuple(clock, timestamp, worker.id, task))
if len(taskheap) > maxtasks:
heappop(taskheap)
handler = getattr(task, 'on_' + type, None)
if type == 'received':
self.task_count += 1
if handler:
handler(**fields)
else:
task.on_unknown_event(type, **fields)
return created
def _dispatch_event(self, event, kwdict=kwdict):
self.event_count += 1
event = kwdict(event)
group, _, subject = event['type'].partition('-')
try:
self._get_handler(group)(subject, event)
except KeyError:
pass
if self.event_callback:
self.event_callback(self, event)
[docs] def itertasks(self, limit=None):
for index, row in enumerate(items(self.tasks)):
yield row
if limit and index + 1 >= limit:
break
[docs] def tasks_by_time(self, limit=None):
"""Generator giving tasks ordered by time,
in ``(uuid, Task)`` tuples."""
seen = set()
for evtup in islice(reversed(self._taskheap), 0, limit):
uuid = evtup[3].uuid
if uuid not in seen:
yield uuid, evtup[3]
seen.add(uuid)
tasks_by_timestamp = tasks_by_time
[docs] def tasks_by_type(self, name, limit=None):
"""Get all tasks by type.
Return a list of ``(uuid, Task)`` tuples.
"""
return islice(
((uuid, task) for uuid, task in self.tasks_by_time()
if task.name == name),
0, limit,
)
[docs] def tasks_by_worker(self, hostname, limit=None):
"""Get all tasks by worker.
"""
return islice(
((uuid, task) for uuid, task in self.tasks_by_time()
if task.worker.hostname == hostname),
0, limit,
)
[docs] def task_types(self):
"""Return a list of all seen task types."""
return list(sorted(set(task.name for task in values(self.tasks)
if task.name is not None)))
[docs] def alive_workers(self):
"""Return a list of (seemingly) alive workers."""
return [w for w in values(self.workers) if w.alive]
def __repr__(self):
return R_STATE.format(self)
def __reduce__(self):
return self.__class__, (
self.event_callback, self.workers, self.tasks, self._taskheap,
self.max_workers_in_memory, self.max_tasks_in_memory,
)