The 'memcached_host_lookup_failure' error occurs when Memcached server is unable to resolve the hostname or IP address of the specified Memcached server. The issue could be caused by a variety of reasons, such as incorrect DNS configuration, network connectivity problems or wrong IP/hostname provided during configuration. Additionally, if the Memcached server is not running or is unreachable due to firewall blocking, this error may also occur.
To resolve the 'memcached_host_lookup_failure' error, you can start by ensuring that the hostname or IP address of the Memcached server is correct and accessible from the server where the Memcached client is running. Verify the DNS settings and ensure that the server is reachable using ping or telnet.
If the hostname or IP address is correct and reachable, then check if the Memcached server is running and accessible on the specified port. It's also important to check if there are any firewalls or access restrictions that might be blocking the connection. Try disabling firewalls temporarily to see if it resolves the issue.
Another option is to verify the Memcached configuration file and ensure that the configuration options are set correctly. Ensure that the server and port are correctly set in the configuration file. Finally, try restarting both the Memcached server and client to see if it resolves the issue.