Sometimes Centrestack server cannot connect to MySQL.
When try to connect to MySQL via MySQL Workbench installed on the Centrestack server, got error 'Host is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts'
When hit the error, need to unblock the Centrestack server first.
On the MySQL Server, if you can connect to MySQL, try the following:
mysql> SET GLOBAL max_connect_errors = 100000000;
mysql> FLUSH HOSTS;
if you can not connect to mysql try this:
if it still doesn't work:
mysqladmin flush-hosts -u [username] -p
After unblock the connect, on all worker nodes, run 'iisreset', to restart IIS