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Databases

Almost all OpenStack components have an underlying database to store persistent information. Usually this database is MySQL. Normal MySQL administration is applicable to these databases. OpenStack does not configure the databases out of the ordinary. Basic administration includes performance tweaking, high availability, backup, recovery, and repairing. For more information, see a standard MySQL administration guide.

You can perform a couple of tricks with the database to either more quickly retrieve information or fix a data inconsistency error—for example, an instance was terminated, but the status was not updated in the database. These tricks are discussed throughout this book.

Database Connectivity

Review the component’s configuration file to see how each OpenStack component accesses its corresponding database. Look for a connection option. The following command uses grep to display the SQL connection string for nova, glance, cinder, and keystone:

# grep -hE "connection ?=" \
  /etc/nova/nova.conf /etc/glance/glance-*.conf \
  /etc/cinder/cinder.conf /etc/keystone/keystone.conf \
  /etc/neutron/neutron.conf
connection = mysql+pymysql://nova:password@cloud.example.com/nova
connection = mysql+pymysql://glance:password@cloud.example.com/glance
connection = mysql+pymysql://glance:password@cloud.example.com/glance
connection = mysql+pymysql://cinder:password@cloud.example.com/cinder
connection = mysql+pymysql://keystone:password@cloud.example.com/keystone
connection = mysql+pymysql://neutron:password@cloud.example.com/neutron

The connection strings take this format:

mysql+pymysql:// <username> : <password> @ <hostname> / <database name>

Performance and Optimizing

As your cloud grows, MySQL is utilized more and more. If you suspect that MySQL might be becoming a bottleneck, you should start researching MySQL optimization. The MySQL manual has an entire section dedicated to this topic: Optimization Overview.