Installation guide

92 Chapter 5:Database Services

in the cluster environment. This will ensure that failover is transparent to database client application

programs and does not require programs to reconnect.

5.3 Setting Up a MySQL Service

A database service can serve highly-available data to a MySQL database application. The application

can then provide network access to database client systems, such as Web servers. If the service fails

over, the application accesses the shared database data through the new cluster system. A network-

accessible database service is usually assigned one IP address, which is failed over along with the

service to maintain transparent access for clients.

An example of a MySQL database service is as follows:

• The MySQL server and the database instance both reside on a file system that is located on a disk

partition on shared storage. This allows the database data and its run-time state information, which

is required for failover, to be accessed by both cluster systems. In the example, the file system is

mounted as /var/mysql, using the shared disk partition /dev/sda1.

• An IP address is associated with the MySQL database to accommodate network access by clients

of the database service. This IP address will automatically be migrated among the cluster members

as the service fails over. In the example below, the IP address is 10.1.16.12.

• The script that is used to start and stop the MySQL database is the standard System V init

script, which has been modified with configuration parameters to match the file system on which

the database is installed.

• By default, a client connection to a MySQL server will time out after eight hours of inactivity.

This connection limit can be modified by setting the wait_timeout variable when you start

mysqld. For example, to set timeouts to 4 hours, start the MySQL daemon as follows:

mysqld -O wait_timeout=14400

To check if a MySQL server has timed out, invoke the mysqladmin version command and

examine the uptime. Invoke the query again to automatically reconnect to the server.

Depending on the Linux distribution, one of the following messages may indicate a MySQL server

timeout:

CR_SERVER_GONE_ERROR

CR_SERVER_LOST

A sample script to start and stop the MySQL database is located in /usr/share/clus-

ter/doc/services/examples/mysql.server, and is shown below:

#!/bin/sh

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