Primero, permítanme comenzar que he buscado en muchos sitios sobre la forma "correcta" de configurar múltiples fuentes de datos en Grails, cada uno de ellos (con Grails 2.0 y posterior) apuntando aldocs, sin embargo, después de hacer lo que dice la documentación me sale este error:

Error 2014-03-29 15:48:29,219 [localhost-startStop-1] ERROR context.GrailsContextLoader      - Error initializing the application: Error creating bean with name 'transactionManager_lookup': Cannot resolve reference to bean 'sessionFactory_lookup' while setting bean property 'sessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory_lookup': Cannot resolve reference to bean 'transactionManager' while setting bean property 'transactionManager'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'transactionManager': Cannot resolve reference to bean '$primaryTransactionManager' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name '$primaryTransactionManager': Cannot resolve reference to bean 'sessionFactory' while setting bean property 'sessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory': Cannot resolve reference to bean 'transactionManager' while setting bean property 'transactionManager'; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'transactionManager': Requested bean is currently in creation: Is there an unresolvable circular reference?
Message: Error creating bean with name 'transactionManager_lookup': Cannot resolve reference to bean 'sessionFactory_lookup' while setting bean property 'sessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory_lookup': Cannot resolve reference to bean 'transactionManager' while setting bean property 'transactionManager'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'transactionManager': Cannot resolve reference to bean '$primaryTransactionManager' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name '$primaryTransactionManager': Cannot resolve reference to bean 'sessionFactory' while setting bean property 'sessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory': Cannot resolve reference to bean 'transactionManager' while setting bean property 'transactionManager'; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'transactionManager': Requested bean is currently in creation: Is there an unresolvable   circular reference?

Lo que me parece más interesante es que si especifico:

dataSource_lookup

Obtendré:

Error initializing the application: Error creating bean with name     'transactionManager_lookup'

Y si lo cambio a:

dataSource_mysqldb

Yo obtengo:

Error initializing the application: Error creating bean with name 'transactionManager_mysqldb'

Si no especifico una segunda fuente de datos, todo funciona bien.

Mi código:

dataSource {
 logSql = true
 pooled = true
 dialect = org.hibernate.dialect.MySQLInnoDBDialect
 driverClassName = 'com.mysql.jdbc.Driver'
 username = 'myuser'
 password = 'mypass'
 url = 'jdbc:mysql://localhost/mydatabase'
 dbCreate = 'update'
}

dataSource_mysql {
 dialect = org.hibernate.dialect.MySQLInnoDBDialect
 driverClassName = 'com.mysql.jdbc.Driver'
 username = 'myuser'
 password = 'mypass'
 url = 'jdbc:mysql://localhost/mydatabase'
 dbCreate = 'update'
}

dataSource_oracle {
 dialect = org.hibernate.dialect.Oracle10gDialect
 driverClassName = 'oracle.jdbc.driver.OracleDriver'
 username = 'myuser'
 password = 'mypass'
 url = 'jdbc:oracle:thin:@localhost:1521:mydatabase'
 dbCreate = 'update'
}

¿Qué estoy haciendo mal aquí? (Como se indicó anteriormente, si elimino los dos dataSources secundarios (dataSource_mysql y dataSource_oracle) todo funciona bien).

Gracias por adelantado. Dev: Ubuntu - Grails 2.3.7 - MySQL - Oracle 11g.