grails-data-mongodb/docs/src/docs/asciidoc/multiTenancy/dynamicConnectionSources.adoc

=== Dynamic ConnectionSources
If you are using a multi-tenancy mode of `DATABASE` then by default the expectation is that all tenants are configured in your `application.yml` file.

However, it is possible read your Mongo client connection sources dynamically using link:../api/org/grails/datastore/mapping/mongo/connections/MongoConnectionSources.html[MongoConnectionSources].

The `MongoConnectionSources` class will read the mongo client configurations from a Mongo collection called `mongo.connections` by default. To configure it you must specify the `connectionSourcesClass` in `application.yml`:

[source,yaml]
----
grails:
    mongodb:
        multiTenancy:
            mode: DATABASE
        connectionSourcesClass: org.grails.datastore.mapping.mongo.connections.MongoConnectionSources
        connectionsCollection: "myconnections"
...
----

You can then even add new connections at runtime using the `ConnectionSources` API:

[source,groovy]
----
import grails.gorm.multitenancy.*

@Autowired MongoDatastore mongoDatastore
...
def configuration = [url:"mongodb://localhost/moreBooks"]
MongoClient mongoClient =
        mongoDatastore.connectionSources
					  .addConnectionSource("moreBooks", configuration)
----

All new connection sources will be stored within the specified `connectionsCollection` and if the application is restarted will read from the `connectionsCollection`.

WARNING: GORM for MongoDB does not implement provisioning of new MongoDB instances at runtime. This is something that would need to be implemented by a cloud services provider for example.