This post is an update to my previous post on setting up SMX4 with high availability in mind.
Since the transition to Apache Felix Karaf the support for more database locking table back ends has expanded. Specifically you can now use Apache Derby, MySQL, or a generic JDBC connector. The Derby and Generic JDBC locks make use of the 'FOR UPDATE' feature common to many databases. The MySQL lock however makes use of the ' LOCK TABLES' directive, this is due to the 'FOR UPDATE' command not returning a ResultSet on more recent versions of MySQL (see some discussions on this here).
The following system.properties configuration will allow your Karaf based SMX4 instance to use a MySQL JDBC lock:
karaf.lock=true
karaf.lock.level=20
karaf.lock.delay=1000
karaf.lock.class=org.apache.felix.karaf.main.MySQLJDBCLock
karaf.lock.jdbc.url=jdbc:mysql://address:port/dbname
karaf.lock.jdbc.driver=com.mysql.jdbc.Driver
karaf.lock.jdbc.user=root
karaf.lock.jdbc.password=karaf
karaf.lock.jdbc.table=KARAF_LOCK
karaf.lock.jdbc.clustername=mycluster
karaf.lock.jdbc.timeout=30
Please note that the MySQL JDBC driver will have to be made available on the classpath.
