The error "celery cannot connect to amqp redis" occurs when the Celery task queue is unable to establish a connection with the Redis message broker, which is acting as an AMQP (Advanced Message Queuing Protocol) broker. This problem can arise due to various reasons such as incorrect configuration settings in Celery or Redis, network issues like firewalls blocking communication between Celery and Redis, outdated Celery or Redis versions, or Redis being down or unresponsive.
To resolve this issue, first ensure that your Celery and Redis configurations are correct, including matching hostnames, ports, and authentication details. If you're still encountering problems, verify that your network setup allows communication between Celery and Redis, checking for potential firewall restrictions. Ensure both Celery and Redis are up-to-date with compatible versions, and if necessary, update them. Finally, confirm that the Redis server is running and accessible by reviewing its logs and using tools like
redis-cli ping to test connectivity. If needed, restart the Redis server to restore functionality.