Within composite clusters, both Composite Active/Passive and Composite Active/Active, the
selection of datasources can be made to be deterministic by specifying
the list of datasources within the user.map
configuration. The configuration is based on an ordered, comma-separated
list of services to use which are then selected in order.
The format of the specification is as follows:
user passcompositeDSdataservice_by_order_of_priority* [-dataservice_to_exclude]*
The specification operates on the following rules:
List of service names in order
If the service name has a dash prefix it is always explicitly excluded from the list of available datasources
If a datasource is not specified, it will always be picked last
For example, in a setup made of three data service,
usa,
asia and
europe using the following
configuration:
app_user secret usa,asia,-europe
Will select data sources in data service
usa. If
usa is not available, in
asia. If
asia is not availble, then
connection will not succeed since
europe has been negated.