CREATE TABLE t1 (id INT PRIMARY KEY) ENGINE=InnoDB;
connection node_2;
SET GLOBAL read_only=TRUE;
connection node_1;
INSERT INTO t1 VALUES (1);
connection node_2;
SELECT COUNT(*) = 1 FROM t1;
COUNT(*) = 1
1
CREATE USER foo@localhost;
# Open connection to node 2 using 'foo' user.
connect foo_node_2,127.0.0.1,foo,,test,$port_2,;

# Connect with foo_node_2
connection foo_node_2;
INSERT INTO t1 VALUES (2);
ERROR HY000: The MariaDB server is running with the --read-only option so it cannot execute this statement
connection node_2;
SELECT COUNT(*) = 1 FROM t1;
COUNT(*) = 1
1
SET GLOBAL read_only=FALSE;
DROP TABLE t1;
DROP USER foo@localhost;