There can be several causes behind the 'redis cluster replication not working' error:
Network Problems: Replication in Redis Cluster involves communication between different nodes. If your network has issues such as slow speeds, interference, or even a complete outage, this could cause replication to fail.
Configuration Issues: Incorrect configuration of the Redis Cluster can disrupt replication. This includes incorrect settings for
cluster-node-timeout (node is considered unreachable after this amount of time), using wrong IP addresses, or specifying wrong ports.
Insufficient Resources: Redis needs enough system resources (memory and CPU) to function efficiently. If your system doesn't have enough resources, this could lead to replication issues.
Redis Version Incompatibility: If you are running different versions of Redis on master and slave nodes, it may lead to inconsistencies and replication failures.
Depending on the root cause identified above, here are some potential solutions:
Fix Network Issues: Ensure that all nodes have stable and fast network connections. You may need to contact your network administrator or ISP if you suspect network problems.
Correct Configuration: Review your Redis Cluster configuration. Make sure all IP addresses and ports are correctly specified, and check that the
cluster-node-timeout is set to a suitable value. Ensure that the
slaveof directives are correctly pointing to the corresponding masters.
Allocate Sufficient Resources: Monitor your system's usage of memory and CPU. If necessary, you might need to upgrade your hardware or reconfigure your system to provide more resources to Redis.
Upgrade Redis Versions: If you're running different Redis versions on master and slave nodes, consider upgrading them to the same version. Always go for the latest stable version of Redis.
Also, it's important to consult logs for more specific error messages, which can give more detailed insights into what exactly is causing the replication issue.