As mentioned in
Connection Volume Management, to
allow for the need to perform administrative operations even
when max_connections
connections are already established on the interfaces used for
ordinary connections, the MySQL server permits a single
administrative connection to users who have the
CONNECTION_ADMIN
privilege (or
the deprecated SUPER
privilege).
Additionally, as of MySQL 8.0.14, the server permits dedicating a TCP/IP port for administrative connections, as described in the following sections.
The administrative connection interface has these characteristics:
The server enables the interface only if the
admin_address
system variable is set at startup to indicate the IP address for it. Ifadmin_address
is not set, the server maintains no administrative interface.The
admin_port
system variable specifies the interface TCP/IP port number (default 33062).There is no limit on the number of administrative connections.
Connections are permitted only for users who have the
SERVICE_CONNECTION_ADMIN
privilege.The
create_admin_listener_thread
system variable enables DBAs to choose at startup whether the administrative interface has its own separate thread. The default isOFF
; that is, the manager thread for ordinary connections on the main interface also handles connections for the administrative interface.
These lines in the server my.cnf
file
enable the administrative interface on the loopback interface
and configure it to use port number 33064 (that is, a port
different from the default):
[mysqld]
admin_address=127.0.0.1
admin_port=33064
MySQL client programs connect to either the main or administrative interface by specifying appropriate connection parameters. If the server running on the local host is using the default TCP/IP port numbers of 3306 and 33062 for the main and administrative interfaces, these commands connect to those interfaces:
mysql --protocol=TCP --port=3306
mysql --protocol=TCP --port=33062
Prior to MySQL 8.0.21, the administrative interface supports encrypted connections using the connection-encryption configuration that applies to the main interface. As of MySQL 8.0.21, the administrative interface has its own configuration parameters for encrypted connections. These correspond to the main interface parameters but enable independent configuration of encrypted connections for the administrative interface:
The
--admin-ssl
option is like the--ssl
option, but it enables or disables encrypted connections for the administrative interface rather than the main interface.The
admin_tls_
andxxx
admin_ssl_
system variables are like thexxx
tls_
andxxx
ssl_
system variables, but they configure the TLS context for the administrative interface rather than the main interface.xxx
For general information about configuring connection-encryption support, see Section 6.3.1, “Configuring MySQL to Use Encrypted Connections”. That discussion is written for the main connection interface, but the parameter names are similar for the administrative connection interface. The following remarks provide information specific to the administrative interface.
TLS configuration for the administrative interface follows these rules:
If
--admin-ssl
is enabled (the default), the administrative interface supports encrypted connections. For connections on the interface, the applicable TLS context depends on whether any nondefault administrative TLS parameter is configured:If all administrative TLS parameters have their default values, the administrative interface uses the same TLS context as the main interface.
If any administrative TLS parameter has a nondefault value, the administrative interface uses the TLS context defined by its own parameters. (This is the case if any
admin_tls_
orxxx
admin_ssl_
system variable is set to a value different from its default.) If a valid TLS context cannot be created from those parameters, the administrative interface falls back to the main interface TLS context.xxx
If
--admin-ssl
is disabled, encrypted connections to the administrative interface are disabled. (This is true even if administrative TLS parameters have nondefault values because disabling--admin-ssl
takes precedence.)
Examples:
This configuration in the server
my.cnf
file enables the administrative interface, but does not set any of the TLS parameters specific to that interface:[mysqld] admin_address=127.0.0.1
As a result, the administrative interface supports encrypted connections (because encryption is supported by default when the administrative interface is enabled), but uses the main interface TLS context. When clients connect to the administrative interface, they should use the same certificate and key files as for ordinary connections on the main interface. For example (enter the command on a single line):
mysql --protocol=TCP --port=33062 --ssl-ca=ca.pem --ssl-cert=client-cert.pem --ssl-key=client-key.pem
This server configuration enables the administrative interface and sets the TLS certificate and key file parameters specific to that interface:
[mysqld] admin_address=127.0.0.1 admin_ssl_ca=admin-ca.pem admin_ssl_cert=admin-server-cert.pem admin_ssl_key=admin-server-key.pem
As a result, the administrative interface supports encrypted connections using its own TLS context. When clients connect to the administrative interface, they should use certificate and key files specific to that interface. For example (enter the command on a single line):
mysql --protocol=TCP --port=33062 --ssl-ca=admin-ca.pem --ssl-cert=admin-client-cert.pem --ssl-key=admin-client-key.pem
This server configuration enables the administrative interface but disables encrypted connections for it:
[mysqld] admin-ssl=OFF admin_address=127.0.0.1
In this case, if the configuration were to also set administrative TLS parameters such as
admin_ssl_ca
, those parameter settings would have no effect becauseadmin-ssl=OFF
takes precedence.