This document describes the current stable version of Celery (5.2). For development docs, go here.

Source code for

"""Task Routing.

Contains utilities for working with task routers, (:setting:`task_routes`).
import fnmatch
import re
from collections import OrderedDict
from import Mapping

from kombu import Queue

from celery.exceptions import QueueNotFound
from celery.utils.collections import lpmerge
from celery.utils.functional import maybe_evaluate, mlazy
from celery.utils.imports import symbol_by_name

    Pattern = re._pattern_type
except AttributeError:  # pragma: no cover
    # for support Python 3.7
    Pattern = re.Pattern

__all__ = ('MapRoute', 'Router', 'prepare')

[docs]class MapRoute: """Creates a router out of a :class:`dict`.""" def __init__(self, map): map = map.items() if isinstance(map, Mapping) else map = {} self.patterns = OrderedDict() for k, v in map: if isinstance(k, Pattern): self.patterns[k] = v elif '*' in k: self.patterns[re.compile(fnmatch.translate(k))] = v else:[k] = v def __call__(self, name, *args, **kwargs): try: return dict([name]) except KeyError: pass except ValueError: return {'queue':[name]} for regex, route in self.patterns.items(): if regex.match(name): try: return dict(route) except ValueError: return {'queue': route}
[docs]class Router: """Route tasks based on the :setting:`task_routes` setting.""" def __init__(self, routes=None, queues=None, create_missing=False, app=None): = app self.queues = {} if queues is None else queues self.routes = [] if routes is None else routes self.create_missing = create_missing
[docs] def route(self, options, name, args=(), kwargs=None, task_type=None): kwargs = {} if not kwargs else kwargs options = self.expand_destination(options) # expands 'queue' if self.routes: route = self.lookup_route(name, args, kwargs, options, task_type) if route: # expands 'queue' in route. return lpmerge(self.expand_destination(route), options) if 'queue' not in options: options = lpmerge(self.expand_destination(, options) return options
[docs] def expand_destination(self, route): # Route can be a queue name: convenient for direct exchanges. if isinstance(route, str): queue, route = route, {} else: # can use defaults from configured queue, but override specific # things (like the routing_key): great for topic exchanges. queue = route.pop('queue', None) if queue: if isinstance(queue, Queue): route['queue'] = queue else: try: route['queue'] = self.queues[queue] except KeyError: raise QueueNotFound( f'Queue {queue!r} missing from task_queues') return route
[docs] def lookup_route(self, name, args=None, kwargs=None, options=None, task_type=None): query = self.query_router for router in self.routes: route = query(router, name, args, kwargs, options, task_type) if route is not None: return route
[docs] def query_router(self, router, task, args, kwargs, options, task_type): router = maybe_evaluate(router) if hasattr(router, 'route_for_task'): # pre 4.0 router class return router.route_for_task(task, args, kwargs) return router(task, args, kwargs, options, task=task_type)
def expand_router_string(router): router = symbol_by_name(router) if hasattr(router, 'route_for_task'): # need to instantiate pre 4.0 router classes router = router() return router
[docs]def prepare(routes): """Expand the :setting:`task_routes` setting.""" def expand_route(route): if isinstance(route, (Mapping, list, tuple)): return MapRoute(route) if isinstance(route, str): return mlazy(expand_router_string, route) return route if routes is None: return () if not isinstance(routes, (list, tuple)): routes = (routes,) return [expand_route(route) for route in routes]