Charmed MySQL Explanations - Users

Charm Users explanations

There are two types of users in MySQL:

  • Internal users (used by charm operator)
  • Relation/integration users (used by related applications)
    • Extra user roles (if default permissions are not enough)

Internal users explanations:

The operator uses the following internal DB users:

  • root - the initial/default MySQL user. Used for very initial bootstrap only.
  • clusteradmin - the user to manage entire MySQL InnoDB ClusterSet.
  • serverconfig - the user to manage local MySQL instance.
  • monitoring - the user for COS integration.
  • backups - the user to perform/list/restore backups.
  • mysql_innodb_cluster_####### - the internal recovery users which enable connections between the servers in the cluster. Dedicated user created for each Juju unit/InnoDB Cluster member.
  • mysql_innodb_cs_####### - the internal recovery user which enable connections between MySQl InnoDB Clusters in ClusterSet. One user is created for entire MySQL ClusterSet.

The full list of internal users is available in charm source code. The full dump of internal mysql.user table (on newly installed charm):

mysql> select Host,User,account_locked from mysql.user;
| Host      | User                            | account_locked |
| %         | backups                         | N              |
| %         | clusteradmin                    | N              |
| %         | monitoring                      | N              |
| %         | mysql_innodb_cluster_2277159043 | N              |
| %         | mysql_innodb_cluster_2277159122 | N              |
| %         | mysql_innodb_cluster_2277159949 | N              |
| %         | mysql_innodb_cs_f8ead780        | N              |
| %         | serverconfig                    | N              |
| localhost | mysql.infoschema                | Y              |
| localhost | mysql.session                   | Y              |
| localhost | mysql.sys                       | Y              |
| localhost | root                            | N              |
10 rows in set (0.00 sec)

Note: it is forbidden to use/manage described above users! They are dedicated to the operators logic! Please use data-integrator charm to generate/manage/remove an external credentials.

It is allowed to rotate passwords for internal users using action ‘set-password’

> juju show-action mysql set-password
Change the system user's password, which is used by charm. It is for internal charm users and SHOULD NOT be used by applications.

  type: string
  description: The password will be auto-generated if this option is not specified.
  type: string
  description: The username, the default value 'root'. Possible values - root,
    serverconfig, clusteradmin.

For example, to generate a new random password for internal user:

> juju run-action --wait mysql/leader set-password username=clusteradmin
  results: {}
  status: completed

> juju run-action --wait mysql/leader get-password username=clusteradmin
    password: PFLIwiwy0Pn7n7xgYtXKw39H
    username: clusteradmin

To set a predefined password for the specific user, run:

> juju run-action --wait mysql/leader set-password username=clusteradmin password=newpassword
  results: {}
  status: completed

> juju run-action --wait mysql/leader get-password username=clusteradmin
  UnitId: mysql/3
  id: "14"
    password: newpassword
    username: clusteradmin

Note: the action set-password must be executed on juju leader unit (to update peer relation data with new value).

Relation/integration users explanations:

The operator created a dedicated user for every application related/integrated with database. Those users are removed on the juju relation/integration removal request. However, DB data stays in place and can be reused on re-created relations (using new user credentials):

mysql> select Host,User,account_locked from mysql.user where User like 'relation%';
| Host | User       | account_locked |
| %    | relation-8 | N              |
| %    | relation-9 | N              |
2 row in set (0.00 sec)

The extra user(s) will be created for relation with mysql-router charm to provide necessary users for applications related via mysql-router app:

mysql> select Host,User,account_locked from mysql.user where User like 'mysql_router%';
| Host | User                       | account_locked |
| %    | mysql_router1_gwa0oy6xnp8l | N              |
1 row in set (0.00 sec)

Note: If password rotation is needed for users used in relations, it is needed to remove the relation and create it again:

> juju remove-relation mysql myclientapp
> juju wait-for application mysql
> juju relate mysql myclientapp

Extra user roles

When an application charm requests a new user through the relation/integration it can specify that the user should have the admin role in the extra-user-roles field. The admin role enables the new user to read and write to all databases (for the mysql system database it can only read data) and also to create and delete non-system databases.

Note: extra-user-roles is supported by modern interface mysql_client only and missing for legacy mysql interface. Read more about the supported charm interfaces here.