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Cannot connect to redis 6.0 as broker if username supplied in url

See original GitHub issue

Similar to https://github.com/celery/celery/issues/6422. Fixed for Celery backend only in 5.1.2

There is a problem with broker connections to redis6 where authentication to a username is required.

for code such as

from celery import Celery
url = "rediss://someuser:somepassword@somehost.databases.appdomain.cloud:31349"
app = Celery('tasks', broker=url,
    result_backend=url,
    broker_use_ssl = {
        'ssl_cert_reqs': 'required',
        'ssl_ca_certs': '/home/showcase/rediscelery/cert.crt'
    },
    redis_backend_use_ssl = {
        'ssl_cert_reqs': 'required',
        'ssl_ca_certs': '/home/showcase/rediscelery/cert.crt'
    }
)

you get the error

[2021-10-18 15:49:19,184: ERROR/MainProcess] consumer: Cannot connect to rediss://someuser:**@somehost.databases.appdomain.cloud:31349//: WRONGPASS invalid username-password pair.
Trying again in 2.00 seconds... (1/100)

This is caused by kombu not extracting the username from the URL.

The relevant file is kombu/transport/redis.py. The following fix is suggested, add 'username': conninfo.userid, to connparams assignment as

   def _connparams(self, asynchronous=False):
        conninfo = self.connection.client
        connparams = {
            'host': conninfo.hostname or '127.0.0.1',
            'port': conninfo.port or self.connection.default_port,
            'virtual_host': conninfo.virtual_host,
            'username': conninfo.userid,
            'password': conninfo.password,
            'max_connections': self.max_connections,
            'socket_timeout': self.socket_timeout,
            'socket_connect_timeout': self.socket_connect_timeout,
            'socket_keepalive': self.socket_keepalive,
            'socket_keepalive_options': self.socket_keepalive_options,
            'health_check_interval': self.health_check_interval,
            'retry_on_timeout': self.retry_on_timeout,
        }