Package: channels-redis
Provides Django Channels channel layers that use Redis as a backing store.There are two available implementations:RedisChannelLayeris the original layer, and implements channel and group
handling itself.RedisPubSubChannelLayeris newer and leverages Redis Pub/Sub for message
dispatch. This layer is currently atBetastatus, meaning it may be subject
to breaking changes whilst it matures.Both layers support a single-server and sharded configurations.channels_redisis tested against Python 3.8 to 3.12,redis-pyversions 4.6,
5.0, and the development branch, and Channels versions 3, 4 and the development
branch there.Installationpip install channels-redisNote:Prior versions of this package were calledasgi_redisand are
still available under PyPI as that name if you need them for Channels 1.x projects.
This package is for Channels 2 projects only.UsageSet up the channel layer in your Django settings file like so:CHANNEL_LAYERS={"default":{"BACKEND":"channels_redis.core.RedisChannelLayer","CONFIG":{"hosts":[("localhost",6379)],},},}Or, you can use the alternate implementation which uses Redis Pub/Sub:CHANNEL_LAYERS={"default":{"BACKEND":"channels_redis.pubsub.RedisPubSubChannelLayer","CONFIG":{"hosts":[("localhost",6379)],},},}Possible options forCONFIGare listed below.hostsThe server(s) to connect to, as either URIs,(host, port)tuples, or dicts conforming toredis Connection.
Defaults toredis://localhost:6379. Pass multiple hosts to enable sharding,
but note that changing the host list will lose some sharded data.SSL connections that are self-signed (ex: Heroku):"default":{"BACKEND":"channels_redis.pubsub.RedisPubSubChannelLayer","CONFIG":{"hosts":[{"address":"rediss://user@host:port",# "REDIS_TLS_URL""ssl_cert_reqs":None,}]}}Sentinel connections require dicts conforming to:{
    "sentinels": [
        ("localhost", 26379),
    ],
    "master_name": SENTINEL_MASTER_SET,
    **kwargs
}note the additionalmaster_namekey specifying the Sentinel master set and any additional connection kwargs can also be passed. Plain Redis and Sentinel connections can be mixed and matched if
sharding.If your server is listening on a UNIX domain socket, you can also use that to connect:["unix:///path/to/redis.sock"].
This should be slightly faster than a loopback TCP connection.prefixPrefix to add to all Redis keys. Defaults toasgi. If you’re running
two or more entirely separate channel layers through the same Redis instance,
make sure they have different prefixes. All servers talking to the same layer
should have the same prefix, though.expiryMessage expiry in seconds. Defaults to60. You generally shouldn’t need
to change this, but you may want to turn it down if you have peaky traffic you
wish to drop, or up if you have peaky traffic you want to backlog until you
get to it.group_expiryGroup expiry in seconds. Defaults to86400. Channels will be removed
from the group after this amount of time; it’s recommended you reduce it
for a healthier system that encourages disconnections. This value should
not be lower than the relevant timeouts in the interface server (e.g.
the--websocket_timeouttodaphne).capacityDefault channel capacity. Defaults to100. Once a channel is at capacity,
it will refuse more messages. How this affects different parts of the system
varies; a HTTP server will refuse connections, for example, while Django
sending a response will just wait until there’s space.channel_capacityPer-channel capacity configuration. This lets you tweak the channel capacity
based on the channel name, and supports both globbing and regular expressions.It should be a dict mapping channel name pattern to desired capacity; if the
dict key is a string, it’s intepreted as a glob, while if it’s a compiledreobject, it’s treated as a regular expression.This example setshttp.requestto 200, allhttp.response!channels
to 10, and allwebsocket.send!channels to 20:CHANNEL_LAYERS={"default":{"BACKEND":"channels_redis.core.RedisChannelLayer","CONFIG":{"hosts":[("localhost",6379)],"channel_capacity":{"http.request":200,"http.response!*":10,re.compile(r"^websocket.send\!.+"):20,},},},}If you want to enforce a matching order, use anOrderedDictas the
argument; channels will then be matched in the order the dict provides them.symmetric_encryption_keysPass this to enable the optional symmetric encryption mode of the backend. To
use it, make sure you have thecryptographypackage installed, or specify
thecryptographyextra when you installchannels-redis:pip install channels-redis[cryptography]symmetric_encryption_keysshould be a list of strings, with each string
being an encryption key. The first key is always used for encryption; all are
considered for decryption, so you can rotate keys without downtime - just add
a new key at the start and move the old one down, then remove the old one
after the message expiry time has passed.Data is encrypted both on the wire and at rest in Redis, though we advise
you also route your Redis connections over TLS for higher security; the Redis
protocol is still unencrypted, and the channel and group key names could
potentially contain metadata patterns of use to attackers.Keysshould have at least 32 bytes of entropy- they are passed through
the SHA256 hash function before being used as an encryption key. Any string
will work, but the shorter the string, the easier the encryption is to break.If you’re using Django, you may also wish to set this to your site’sSECRET_KEYsetting via theCHANNEL_LAYERSsetting:CHANNEL_LAYERS={"default":{"BACKEND":"channels_redis.core.RedisChannelLayer","CONFIG":{"hosts":["redis://:password@127.0.0.1:6379/0"],"symmetric_encryption_keys":[SECRET_KEY],},},}on_disconnect/on_reconnectThe PubSub layer, which maintains long-running connections to Redis, can drop messages in the event of a network partition.
To handle such situations the PubSub layer accepts optional arguments which will notify consumers of Redis disconnect/reconnect events.
A common use-case is for consumers to ensure that they perform a full state re-sync to ensure that no messages have been missed.CHANNEL_LAYERS={"default":{"BACKEND":"channels_redis.pubsub.RedisPubSubChannelLayer","CONFIG":{"hosts":[...],"on_disconnect":"redis.disconnect",},},}And then in your channels consumer, you can implement the handler:asyncdefredis_disconnect(self,*args):# Handle disconnectDependenciesRedis server >= 5.0 is required forchannels-redis. Python 3.8 or higher is required.Used commandsYour Redis server must support the following commands:RedisChannelLayerusesBZPOPMIN,DEL,EVAL,EXPIRE,KEYS,PIPELINE,ZADD,ZCOUNT,ZPOPMIN,ZRANGE,ZREM,ZREMRANGEBYSCORERedisPubSubChannelLayerusesPUBLISH,SUBSCRIBE,UNSUBSCRIBELocal DevelopmentYou can run the necessary Redis instances in Docker with the following commands:$dockernetworkcreateredis-network$dockerrun--rm\--network=redis-network\--name=redis-server\-p6379:6379\redis$dockerrun--rm\--networkredis-network\--nameredis-sentinel\-eREDIS_MASTER_HOST=redis-server\-eREDIS_MASTER_SET=sentinel\-eREDIS_SENTINEL_QUORUM=1\-p26379:26379\bitnami/redis-sentinelContributingPlease refer to themain Channels contributing docs.
That also contains advice on how to set up the development environment and run the tests.Maintenance and SecurityTo report security issues, please contactsecurity@djangoproject.com. For GPG
signatures and more security process information, seehttps://docs.djangoproject.com/en/dev/internals/security/.To report bugs or request new features, please open a new GitHub issue.This repository is part of the Channels project. For the shepherd and maintenance team, please see themain Channels readme.