This document describes the current stable version of Celery (5.4). For development docs, go here.

Source code for celery.backends.redis

"""Redis result store backend."""
import time
from contextlib import contextmanager
from functools import partial
from urllib.parse import unquote

from kombu.utils.functional import retry_over_time
from kombu.utils.objects import cached_property
from kombu.utils.url import _parse_url, maybe_sanitize_url

from celery import states
from celery._state import task_join_will_block
from celery.canvas import maybe_signature
from celery.exceptions import BackendStoreError, ChordError, ImproperlyConfigured
from celery.result import GroupResult, allow_join_result
from celery.utils.functional import _regen, dictfilter
from celery.utils.log import get_logger
from celery.utils.time import humanize_seconds

from .asynchronous import AsyncBackendMixin, BaseResultConsumer
from .base import BaseKeyValueStoreBackend

    import redis.connection
    from kombu.transport.redis import get_redis_error_classes
except ImportError:
    redis = None
    get_redis_error_classes = None

    import redis.sentinel
except ImportError:

__all__ = ('RedisBackend', 'SentinelBackend')

You need to install the redis library in order to use \
the Redis result store backend.

You need to install the redis library with support of \
sentinel in order to use the Redis result store backend.

Setting ssl_cert_reqs=CERT_OPTIONAL when connecting to redis means that \
celery might not validate the identity of the redis broker when connecting. \
This leaves you vulnerable to man in the middle attacks.

Setting ssl_cert_reqs=CERT_NONE when connecting to redis means that celery \
will not validate the identity of the redis broker when connecting. This \
leaves you vulnerable to man in the middle attacks.

SSL connection parameters have been provided but the specified URL scheme \
is redis://. A Redis SSL connection URL should use the scheme rediss://.

A rediss:// URL must have parameter ssl_cert_reqs and this must be set to \

E_LOST = 'Connection to Redis lost: Retry (%s/%s) %s.'

Retry limit exceeded while trying to reconnect to the Celery redis result \
store backend. The Celery application must be restarted.

logger = get_logger(__name__)

class ResultConsumer(BaseResultConsumer):
    _pubsub = None

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self._get_key_for_task = self.backend.get_key_for_task
        self._decode_result = self.backend.decode_result
        self._ensure = self.backend.ensure
        self._connection_errors = self.backend.connection_errors
        self.subscribed_to = set()

    def on_after_fork(self):
            if self._pubsub is not None:
        except KeyError as e:

    def _reconnect_pubsub(self):
        self._pubsub = None
        # task state might have changed when the connection was down so we
        # retrieve meta for all subscribed tasks before going into pubsub mode
        if self.subscribed_to:
            metas = self.backend.client.mget(self.subscribed_to)
            metas = [meta for meta in metas if meta]
            for meta in metas:
                self.on_state_change(self._decode_result(meta), None)
        self._pubsub = self.backend.client.pubsub(
        # subscribed_to maybe empty after on_state_change
        if self.subscribed_to:
            self._pubsub.connection = self._pubsub.connection_pool.get_connection(
                'pubsub', self._pubsub.shard_hint
            # even if there is nothing to subscribe, we should not lose the callback after connecting.
            # The on_connect callback will re-subscribe to any channels we previously subscribed to.

    def reconnect_on_error(self):
        except self._connection_errors:
                self._ensure(self._reconnect_pubsub, ())
            except self._connection_errors:

    def _maybe_cancel_ready_task(self, meta):
        if meta['status'] in states.READY_STATES:

    def on_state_change(self, meta, message):
        super().on_state_change(meta, message)

    def start(self, initial_task_id, **kwargs):
        self._pubsub = self.backend.client.pubsub(

    def on_wait_for_pending(self, result, **kwargs):
        for meta in result._iter_meta(**kwargs):
            if meta is not None:
                self.on_state_change(meta, None)

    def stop(self):
        if self._pubsub is not None:

    def drain_events(self, timeout=None):
        if self._pubsub:
            with self.reconnect_on_error():
                message = self._pubsub.get_message(timeout=timeout)
                if message and message['type'] == 'message':
                    self.on_state_change(self._decode_result(message['data']), message)
        elif timeout:

    def consume_from(self, task_id):
        if self._pubsub is None:
            return self.start(task_id)

    def _consume_from(self, task_id):
        key = self._get_key_for_task(task_id)
        if key not in self.subscribed_to:
            with self.reconnect_on_error():

    def cancel_for(self, task_id):
        key = self._get_key_for_task(task_id)
        if self._pubsub:
            with self.reconnect_on_error():

[docs] class RedisBackend(BaseKeyValueStoreBackend, AsyncBackendMixin): """Redis task result store. It makes use of the following commands: GET, MGET, DEL, INCRBY, EXPIRE, SET, SETEX """ ResultConsumer = ResultConsumer #: :pypi:`redis` client module. redis = redis connection_class_ssl = redis.SSLConnection if redis else None #: Maximum number of connections in the pool. max_connections = None supports_autoexpire = True supports_native_join = True #: Maximal length of string value in Redis. #: 512 MB - _MAX_STR_VALUE_SIZE = 536870912 def __init__(self, host=None, port=None, db=None, password=None, max_connections=None, url=None, connection_pool=None, **kwargs): super().__init__(expires_type=int, **kwargs) _get = if self.redis is None: raise ImproperlyConfigured(E_REDIS_MISSING.strip()) if host and '://' in host: url, host = host, None self.max_connections = ( max_connections or _get('redis_max_connections') or self.max_connections) self._ConnectionPool = connection_pool socket_timeout = _get('redis_socket_timeout') socket_connect_timeout = _get('redis_socket_connect_timeout') retry_on_timeout = _get('redis_retry_on_timeout') socket_keepalive = _get('redis_socket_keepalive') health_check_interval = _get('redis_backend_health_check_interval') self.connparams = { 'host': _get('redis_host') or 'localhost', 'port': _get('redis_port') or 6379, 'db': _get('redis_db') or 0, 'password': _get('redis_password'), 'max_connections': self.max_connections, 'socket_timeout': socket_timeout and float(socket_timeout), 'retry_on_timeout': retry_on_timeout or False, 'socket_connect_timeout': socket_connect_timeout and float(socket_connect_timeout), } username = _get('redis_username') if username: # We're extra careful to avoid including this configuration value # if it wasn't specified since older versions of py-redis # don't support specifying a username. # Only Redis>6.0 supports username/password authentication. # TODO: Include this in connparams' definition once we drop # support for py-redis<3.4.0. self.connparams['username'] = username if health_check_interval: self.connparams["health_check_interval"] = health_check_interval # absent in redis.connection.UnixDomainSocketConnection if socket_keepalive: self.connparams['socket_keepalive'] = socket_keepalive # "redis_backend_use_ssl" must be a dict with the keys: # 'ssl_cert_reqs', 'ssl_ca_certs', 'ssl_certfile', 'ssl_keyfile' # (the same as "broker_use_ssl") ssl = _get('redis_backend_use_ssl') if ssl: self.connparams.update(ssl) self.connparams['connection_class'] = self.connection_class_ssl if url: self.connparams = self._params_from_url(url, self.connparams) # If we've received SSL parameters via query string or the # redis_backend_use_ssl dict, check ssl_cert_reqs is valid. If set # via query string ssl_cert_reqs will be a string so convert it here if ('connection_class' in self.connparams and issubclass(self.connparams['connection_class'], redis.SSLConnection)): ssl_cert_reqs_missing = 'MISSING' ssl_string_to_constant = {'CERT_REQUIRED': CERT_REQUIRED, 'CERT_OPTIONAL': CERT_OPTIONAL, 'CERT_NONE': CERT_NONE, 'required': CERT_REQUIRED, 'optional': CERT_OPTIONAL, 'none': CERT_NONE} ssl_cert_reqs = self.connparams.get('ssl_cert_reqs', ssl_cert_reqs_missing) ssl_cert_reqs = ssl_string_to_constant.get(ssl_cert_reqs, ssl_cert_reqs) if ssl_cert_reqs not in ssl_string_to_constant.values(): raise ValueError(E_REDIS_SSL_CERT_REQS_MISSING_INVALID) if ssl_cert_reqs == CERT_OPTIONAL: logger.warning(W_REDIS_SSL_CERT_OPTIONAL) elif ssl_cert_reqs == CERT_NONE: logger.warning(W_REDIS_SSL_CERT_NONE) self.connparams['ssl_cert_reqs'] = ssl_cert_reqs self.url = url self.connection_errors, self.channel_errors = ( get_redis_error_classes() if get_redis_error_classes else ((), ())) self.result_consumer = self.ResultConsumer( self,, self.accept, self._pending_results, self._pending_messages, ) def _params_from_url(self, url, defaults): scheme, host, port, username, password, path, query = _parse_url(url) connparams = dict( defaults, **dictfilter({ 'host': host, 'port': port, 'username': username, 'password': password, 'db': query.pop('virtual_host', None)}) ) if scheme == 'socket': # use 'path' as path to the socket… in this case # the database number should be given in 'query' connparams.update({ 'connection_class': self.redis.UnixDomainSocketConnection, 'path': '/' + path, }) # host+port are invalid options when using this connection type. connparams.pop('host', None) connparams.pop('port', None) connparams.pop('socket_connect_timeout') else: connparams['db'] = path ssl_param_keys = ['ssl_ca_certs', 'ssl_certfile', 'ssl_keyfile', 'ssl_cert_reqs'] if scheme == 'redis': # If connparams or query string contain ssl params, raise error if (any(key in connparams for key in ssl_param_keys) or any(key in query for key in ssl_param_keys)): raise ValueError(E_REDIS_SSL_PARAMS_AND_SCHEME_MISMATCH) if scheme == 'rediss': connparams['connection_class'] = redis.SSLConnection # The following parameters, if present in the URL, are encoded. We # must add the decoded values to connparams. for ssl_setting in ssl_param_keys: ssl_val = query.pop(ssl_setting, None) if ssl_val: connparams[ssl_setting] = unquote(ssl_val) # db may be string and start with / like in kombu. db = connparams.get('db') or 0 db = db.strip('/') if isinstance(db, str) else db connparams['db'] = int(db) for key, value in query.items(): if key in redis.connection.URL_QUERY_ARGUMENT_PARSERS: query[key] = redis.connection.URL_QUERY_ARGUMENT_PARSERS[key]( value ) # Query parameters override other parameters connparams.update(query) return connparams @cached_property def retry_policy(self): retry_policy = super().retry_policy if "retry_policy" in self._transport_options: retry_policy = retry_policy.copy() retry_policy.update(self._transport_options['retry_policy']) return retry_policy
[docs] def on_task_call(self, producer, task_id): if not task_join_will_block(): self.result_consumer.consume_from(task_id)
[docs] def get(self, key): return self.client.get(key)
[docs] def mget(self, keys): return self.client.mget(keys)
[docs] def ensure(self, fun, args, **policy): retry_policy = dict(self.retry_policy, **policy) max_retries = retry_policy.get('max_retries') return retry_over_time( fun, self.connection_errors, args, {}, partial(self.on_connection_error, max_retries), **retry_policy)
[docs] def on_connection_error(self, max_retries, exc, intervals, retries): tts = next(intervals) logger.error( E_LOST.strip(), retries, max_retries or 'Inf', humanize_seconds(tts, 'in ')) return tts
[docs] def set(self, key, value, **retry_policy): if isinstance(value, str) and len(value) > self._MAX_STR_VALUE_SIZE: raise BackendStoreError('value too large for Redis backend') return self.ensure(self._set, (key, value), **retry_policy)
def _set(self, key, value): with self.client.pipeline() as pipe: if self.expires: pipe.setex(key, self.expires, value) else: pipe.set(key, value) pipe.publish(key, value) pipe.execute()
[docs] def forget(self, task_id): super().forget(task_id) self.result_consumer.cancel_for(task_id)
[docs] def delete(self, key): self.client.delete(key)
[docs] def incr(self, key): return self.client.incr(key)
[docs] def expire(self, key, value): return self.client.expire(key, value)
[docs] def add_to_chord(self, group_id, result): self.client.incr(self.get_key_for_group(group_id, '.t'), 1)
def _unpack_chord_result(self, tup, decode, EXCEPTION_STATES=states.EXCEPTION_STATES, PROPAGATE_STATES=states.PROPAGATE_STATES): _, tid, state, retval = decode(tup) if state in EXCEPTION_STATES: retval = self.exception_to_python(retval) if state in PROPAGATE_STATES: raise ChordError(f'Dependency {tid} raised {retval!r}') return retval
[docs] def set_chord_size(self, group_id, chord_size): self.set(self.get_key_for_group(group_id, '.s'), chord_size)
[docs] def apply_chord(self, header_result_args, body, **kwargs): # If any of the child results of this chord are complex (ie. group # results themselves), we need to save `header_result` to ensure that # the expected structure is retained when we finish the chord and pass # the results onward to the body in `on_chord_part_return()`. We don't # do this is all cases to retain an optimisation in the common case # where a chord header is comprised of simple result objects. if not isinstance(header_result_args[1], _regen): header_result =*header_result_args) if any(isinstance(nr, GroupResult) for nr in header_result.results):
@cached_property def _chord_zset(self): return self._transport_options.get('result_chord_ordered', True) @cached_property def _transport_options(self): return'result_backend_transport_options', {})
[docs] def on_chord_part_return(self, request, state, result, propagate=None, **kwargs): app = tid, gid, group_index =,, request.group_index if not gid or not tid: return if group_index is None: group_index = '+inf' client = self.client jkey = self.get_key_for_group(gid, '.j') tkey = self.get_key_for_group(gid, '.t') skey = self.get_key_for_group(gid, '.s') result = self.encode_result(result, state) encoded = self.encode([1, tid, state, result]) with client.pipeline() as pipe: pipeline = ( pipe.zadd(jkey, {encoded: group_index}).zcount(jkey, "-inf", "+inf") if self._chord_zset else pipe.rpush(jkey, encoded).llen(jkey) ).get(tkey).get(skey) if self.expires: pipeline = pipeline \ .expire(jkey, self.expires) \ .expire(tkey, self.expires) \ .expire(skey, self.expires) _, readycount, totaldiff, chord_size_bytes = pipeline.execute()[:4] totaldiff = int(totaldiff or 0) if chord_size_bytes: try: callback = maybe_signature(request.chord, app=app) total = int(chord_size_bytes) + totaldiff if readycount == total: header_result = GroupResult.restore(gid) if header_result is not None: # If we manage to restore a `GroupResult`, then it must # have been complex and saved by `apply_chord()` earlier. # # Before we can join the `GroupResult`, it needs to be # manually marked as ready to avoid blocking header_result.on_ready() # We'll `join()` it to get the results and ensure they are # structured as intended rather than the flattened version # we'd construct without any other information. join_func = ( header_result.join_native if header_result.supports_native_join else header_result.join ) with allow_join_result(): resl = join_func( timeout=app.conf.result_chord_join_timeout, propagate=True ) else: # Otherwise simply extract and decode the results we # stashed along the way, which should be faster for large # numbers of simple results in the chord header. decode, unpack = self.decode, self._unpack_chord_result with client.pipeline() as pipe: if self._chord_zset: pipeline = pipe.zrange(jkey, 0, -1) else: pipeline = pipe.lrange(jkey, 0, total) resl, = pipeline.execute() resl = [unpack(tup, decode) for tup in resl] try: callback.delay(resl) except Exception as exc: # pylint: disable=broad-except logger.exception( 'Chord callback for %r raised: %r',, exc) return self.chord_error_from_stack( callback, ChordError(f'Callback error: {exc!r}'), ) finally: with client.pipeline() as pipe: pipe \ .delete(jkey) \ .delete(tkey) \ .delete(skey) \ .execute() except ChordError as exc: logger.exception('Chord %r raised: %r',, exc) return self.chord_error_from_stack(callback, exc) except Exception as exc: # pylint: disable=broad-except logger.exception('Chord %r raised: %r',, exc) return self.chord_error_from_stack( callback, ChordError(f'Join error: {exc!r}'), )
def _create_client(self, **params): return self._get_client()( connection_pool=self._get_pool(**params), ) def _get_client(self): return self.redis.StrictRedis def _get_pool(self, **params): return self.ConnectionPool(**params) @property def ConnectionPool(self): if self._ConnectionPool is None: self._ConnectionPool = self.redis.ConnectionPool return self._ConnectionPool @cached_property def client(self): return self._create_client(**self.connparams) def __reduce__(self, args=(), kwargs=None): kwargs = {} if not kwargs else kwargs return super().__reduce__( args, dict(kwargs, expires=self.expires, url=self.url))
if getattr(redis, "sentinel", None): class SentinelManagedSSLConnection( redis.sentinel.SentinelManagedConnection, redis.SSLConnection): """Connect to a Redis server using Sentinel + TLS. Use Sentinel to identify which Redis server is the current master to connect to and when connecting to the Master server, use an SSL Connection. """
[docs] class SentinelBackend(RedisBackend): """Redis sentinel task result store.""" # URL looks like `sentinel://;sentinel://` _SERVER_URI_SEPARATOR = ";" sentinel = getattr(redis, "sentinel", None) connection_class_ssl = SentinelManagedSSLConnection if sentinel else None def __init__(self, *args, **kwargs): if self.sentinel is None: raise ImproperlyConfigured(E_REDIS_SENTINEL_MISSING.strip()) super().__init__(*args, **kwargs)
[docs] def as_uri(self, include_password=False): """Return the server addresses as URIs, sanitizing the password or not.""" # Allow superclass to do work if we don't need to force sanitization if include_password: return super().as_uri( include_password=include_password, ) # Otherwise we need to ensure that all components get sanitized rather # by passing them one by one to the `kombu` helper uri_chunks = ( maybe_sanitize_url(chunk) for chunk in (self.url or "").split(self._SERVER_URI_SEPARATOR) ) # Similar to the superclass, strip the trailing slash from URIs with # all components empty other than the scheme return self._SERVER_URI_SEPARATOR.join( uri[:-1] if uri.endswith(":///") else uri for uri in uri_chunks )
def _params_from_url(self, url, defaults): chunks = url.split(self._SERVER_URI_SEPARATOR) connparams = dict(defaults, hosts=[]) for chunk in chunks: data = super()._params_from_url( url=chunk, defaults=defaults) connparams['hosts'].append(data) for param in ("host", "port", "db", "password"): connparams.pop(param) # Adding db/password in connparams to connect to the correct instance for param in ("db", "password"): if connparams['hosts'] and param in connparams['hosts'][0]: connparams[param] = connparams['hosts'][0].get(param) return connparams def _get_sentinel_instance(self, **params): connparams = params.copy() hosts = connparams.pop("hosts") min_other_sentinels = self._transport_options.get("min_other_sentinels", 0) sentinel_kwargs = self._transport_options.get("sentinel_kwargs", {}) sentinel_instance = self.sentinel.Sentinel( [(cp['host'], cp['port']) for cp in hosts], min_other_sentinels=min_other_sentinels, sentinel_kwargs=sentinel_kwargs, **connparams) return sentinel_instance def _get_pool(self, **params): sentinel_instance = self._get_sentinel_instance(**params) master_name = self._transport_options.get("master_name", None) return sentinel_instance.master_for( service_name=master_name, redis_class=self._get_client(), ).connection_pool