The new MySQL test in Monit 5.9, connects, read the handshake package from MySQL and then disconnect. One CentOS 6 user reports that the new protocol test generate a
host is blocked because of many connection errors in MySQL.
According to MySQL Documentation this error and subsequent blocking of host happens if
mysqld has received many connection requests from the given host that were interrupted in the middle. It is unclear if Monit's MySQL test which just connect and then disconnect is considered a connection attempt interrupted in the middle. Especially because our test on OSX with MySQL 5.6 and with MySQL 5.5 on Ubuntu does not generate this error.
If you see this error, the workaround until this is clarified is
- Login into MySQL and issue
SET GLOBAL max_connect_errors=4294967295;
Which should buy you at least 135 years before the error is triggered again.