Sometimes, MySQL throws an error like this:

Host ‘…’ is blocked because of many connection errors

Unblock with ‘mysqladmin flush-hosts’

This typically means that MySQL has blocked a host after too many connection errors. The usual fix is to run:

mysqladmin flush-hosts

or

mysql> FLUSH HOSTS; /* deprecated since 8.0.23; invalid in 8.4 */
mysql> TRUNCATE TABLE performance_schema.host_cache; /* recommended since 5.6.5 */

A host is blocked, because of many connection errors, specifically more connection errors than max_connect_errors.

So

• what counts as a connection error?
• what is counted per what?
• and how is the error count cleared?

…

Introduction In this article, I’m going to show you how to optimize the queries executed by a Spring application running on MySQL using Releem. For a short introduction about Releem, check out this previous article, in which I explained how to set up Releem to collect metrics from your MySQL database. Spring Petclinic application The application under test is going to be the well-known Spring Petclinic that we are going to run using the MySQL profile: After starting the application, we are going to run the petclinic_test_plan.jmx JMeter test plan that is... Read More

The post MySQL Query Optimization with Releem appeared first on Vlad Mihalcea.

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