For the check to work, a mysql user with a password must be created within the cluster which the check script can use. The mysql user needs the permissions to be able to run the SQL contained within the check script:

WILDCARD IP ACCEPTABLE:
mysql> CREATE USER 'haproxy'@'%' IDENTIFIED WITH mysql_native_password BY 'secret';
mysql> GRANT USAGE ON *.* TO 'haproxy'@'%';

IP REQUIRED, BRIDGE MODE:
mysql> CREATE USER 'haproxy'@'{ip_of_application_host}' IDENTIFIED WITH mysql_native_password BY 'secret';
mysql> GRANT USAGE ON *.* TO 'haproxy'@'{ip_of_application_host}';

IP REQUIRED, PROXY MODE:
mysql> CREATE USER 'haproxy'@'{ip_of_connector_host}' IDENTIFIED WITH mysql_native_password BY 'secret';
mysql> GRANT USAGE ON *.* TO 'haproxy'@'{ip_of_connector_host}';

If you are running SmartScale the user will also need replication client privilege:

WILDCARD IP ACCEPTABLE:
mysql> GRANT USAGE, REPLICATION CLIENT ON *.* TO 'haproxy'@'%';

IP REQUIRED, BRIDGE MODE:
mysql> GRANT USAGE, REPLICATION CLIENT ON *.* TO 'haproxy'@'{ip_of_application_host}';

IP REQUIRED, PROXY MODE:
mysql> GRANT USAGE, REPLICATION CLIENT ON *.* TO 'haproxy'@'{ip_of_connector_host}';

Add the new user on each connector host by adding the following line to user.map:

haproxy secret cluster_name_here

In the above example, replace cluster_name_here with the name of the actual cluster service.

Create and configure a check script on each host running Tungsten Connector. For example, create the file /opt/continuent/share/connectorchk.sh:

#!/bin/sh
#
# This script checks if a mysql server is healthy running on localhost. It will
# return:
# "HTTP/1.x 200 OK\r" (if mysql is running smoothly)
# - OR -
# "HTTP/1.x 503 Service Unavailable\r" (else)
#
# The purpose of this script is make haproxy capable of monitoring mysql properly
#

MYSQL_HOST=`hostname`
MYSQL_PORT="3306"            #Connector Port
MYSQL_USERNAME="haproxy"
MYSQL_PASSWORD="secret"
MYSQL_OPTS="-N -q -A test"

#If you create the following file, the proxy will return mysql down
#routing traffic to another host
FORCE_FAIL="/dev/shm/proxyoff"
OUT=""
return_ok()
{
echo -e "HTTP/1.1 200 OK\r\n"
echo -e "Content-Type: Content-Type: text/plain\r\n"
echo -e "\r\n"
echo -e "MySQL is running.\r\n"
echo -e "\r\n"
exit 0
}
return_fail()
{
echo -e "HTTP/1.1 503 Service Unavailable\r\n"
echo -e "Content-Type: Content-Type: text/plain\r\n"
echo -e "\r\n"
echo -e "MySQL is *down*.\r\n"
echo -e "$OUT\r\n\r\n"
exit 1
}
if [ -f "$FORCE_FAIL" ]; then
    OUT="$FORCE_FAIL found"
    return_fail;
fi
OUT=`mysql $MYSQL_OPTS --host=$MYSQL_HOST --port=$MYSQL_PORT --user=$MYSQL_USERNAME \
--password=$MYSQL_PASSWORD -e "select @@hostname;" 2>&1`
if [ $? -ne 0 ]; then
    return_fail;
fi

return_ok;

Set the permissions for the check script:

shell> chown tungsten.tungsten /opt/continuent/share/connectorchk.sh
shell> chmod 700 /opt/continuent/share/connectorchk.sh
shell> chmod +x /opt/continuent/share/connectorchk.sh

Install xinetd and add the xinetd service. On RedHat/CentOS:

shell> sudo yum -y install  xinetd telnet

On Debian/Ubuntu:

shell> sudo apt-get install xinetd telnet

Add an entry for the connector check script to /etc/services:

shell> echo "connectorchk         9200/tcp" | sudo tee -a /etc/services

Add a configuration to xinetd by creating the file /etc/xinetd.d/connectorchk as the root user with the following content:

# default: on
# description:connectorchk
service connectorchk
{       
flags           = REUSE
    socket_type     = stream
    port            = 9200
    wait            = no
    user            = tungsten
    server          = /opt/continuent/share/connectorchk.sh
    log_on_failure  += USERID
    disable         = no
#       only_from       = 0.0.0.0/0
# recommended to put the IPs that need
# to connect exclusively (security purposes)
    per_source      = UNLIMITED
}

Now restart xinetd:

shell> sudo service xinetd restart

To verify that the connector check service is running via xinetd, connect to port 9200 using the telnet command:

shell> telnet localhost 9200

You should get a response similar to this:

HTTP/1.1 200 OK

Content-Type: Content-Type: text/plain


MySQL is running.