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We are running Percona MySQL 5.6.30. We've had an issue where a PHP script on a different host was reporting an issue connecting to the database:

Database may be down : SQLSTATE[HY000] [1129] Host 'x.x.x.101' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts'"

We did the flush hosts, and it resolved the issue.

When we went back to check the Percona Audit Logs for the same time, we see a number of connections at that same time, from that same host ('x.x.x.101').

I'm trying to understand how a host could be blocked, and not blocked, at the same time. :) Any ideas?

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That host was blocked because there have been too many connection errors. The maximum number of errors before a host is blocked is represented by the max_connection_errors variable. Before reaching that number of errors, the host was not blocked.

The FLUSH HOSTS commands (or mysqladmin flush-hosts) empties the host cache. After that, the host can connect again and the errors counter is reset.

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  • Agreed. And we have increased the max_connection_errors value. The confusing part is that during this outage, when things were not supposed to be able to connect, we have audit logs that show things connecting. :)
    – Michael Dugas
    Commented Aug 15, 2016 at 15:28
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    Indeed it's confusing. Can you paste here an exact record(s) that shows that? Looking at it, I can try understand what happened.
    – Federico Razzoli
    Commented Aug 17, 2016 at 11:42

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