Error: redis slave not working

What's Causing This Error

The error 'redis slave not working' generally implies that your Redis replica (formerly known as slave) is unable to function correctly, possibly due to one or more of the following reasons:

1. Network Connectivity Issues: The master and slave servers might be experiencing network connectivity problems, which prevent the slave from receiving updates from the master.
2. Insufficient Disk Space: If there isn't enough disk space on the slave server, replication will fail. The slave requires sufficient storage to hold a copy of all data from the master.
3. Configuration Errors: Misconfiguration in the Redis setup could also cause this error. This includes issues like incorrect settings for IP addresses, port numbers, or password authentication.
4. Redis Version Incompatibility: If there are differences in Redis versions between the master and the slave, it can lead to unexpected behavior and failures.

Solution - Here's How To Resolve It

Here are some solutions based on the possible causes mentioned above:

1. Check Network Connectivity: Make sure the master and slave servers can communicate with each other. You can use tools like ping, traceroute, or check firewall settings if necessary.
2. Ensure Enough Disk Space: Ensure there is adequate disk space available on the slave server. You may need to clean up some files or increase the disk size.
3. Verify Configuration: Inspect your Redis configuration files carefully. Check the correctness of IP addresses, port numbers, and if used, password authentication settings. Use CONFIG GET command to inspect the running configuration.
4. Maintain Same Redis Versions: Avoid version incompatibilities by ensuring the master and the slave servers run the same version of Redis.

Remember, it is highly recommended to review your server logs. They can provide more precise information about what's going wrong with your Redis replication setup.