1129: Host 'host' is blocked because of many connection errors
MySQLWhat does it mean?
MySQL blocked a client host after consecutive connection errors from it exceeded the threshold (max_connect_errors). The host was blacklisted because of the handshakes that had failed up to that point.
Why does it happen?
A load balancer/monitoring tool sends incomplete or malformed handshakes to the TCP port; network problems cut connections midway; or a misconfigured client keeps attempting failed connections. When the error counter reaches max_connect_errors, the host is blocked.
How to fix it
Remove the block immediately: in SQL, TRUNCATE TABLE performance_schema.host_cache; (8.0.23+; FLUSH HOSTS was deprecated in 8.0.23 and removed in 8.4) or from the command line, mysqladmin flush-hosts. To see blocked hosts: SELECT host, ip, sum_connect_errors FROM performance_schema.host_cache; Fix the root cause: configure the health check/monitoring tool to perform a full MySQL handshake and check network stability. In healthy environments you can raise max_connect_errors to increase tolerance, but resolving the actual connection errors is what matters.
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