MySQL Cluster Tutorial - cdn.oreillystatic.com

To upgrade MySQL Cluster Manager, all agents can be stopped and new ones started
(using the new software version) with no impact to the continuing operation of the MySQL
Cluster database.
Changes from Previous Approaches to Managing MySQL Cluster
When using MySQL Cluster Manager to manage your MySQL Cluster deployment, the
administrator no longer edits the configuration files (for example config.ini and my.cnf);
instead, these files are created and maintained by the agents. In fact, if those files are
manually edited, the changes will be overwritten by the configuration information which is
held within the agents. Each agent stores all of the cluster configuration data, but it only
creates the configuration files that are required for the nodes that are configured to run on
that host. An example of this is shown in Figure 2 below.
Figure 2: Configuration files created on each host
Similarly when using MySQL Cluster Manager, management actions must not be
performed by the administrator using the ndb_mgm command (which directly connects to
the management node meaning that the agents themselves would not have visibility of any
operations performed with it).
The introduction of MySQL Cluster manager does not remove the need for management
nodes; in particular they continue to perform a number of critical roles:
• When data nodes start up (or are restarted) they connect to the management node(s) to
retrieve their configuration data (the management node in turn fetches that data from
the configuration files created by the agents);
• When stopping or restarting a data node through MySQL Cluster Manager, the state
change is actually performed by the management node;
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