Blocked hosts

When trying to connect to a MySQL instance, a user might get this error:

SQLSTATE[00000] [1129] Host 'XXXX.cern.ch' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts']

There may reasons for this error (please read https://dev.mysql.com/doc/refman/8.0/en/communication-errors.html), the most frequent ones:

• Many errors coming from the same IP: wrong password
• Network glitches that increase wrong connections counter

Possible solutions:

• Contact your admin or egroup admins in order to do a 'mysqladmin flush-hosts'. Please see: https://dev.mysql.com/doc/refman/8.0/en/host-cache.html#blocked-host, this command can be run from any server provided you have the driver to connect to MySQL.
• Increase max_connect_errors server variable: https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_max_connect_errors, default value is 100.