Add support for AbstractRoutingConnectionFactory

[zahidraza]

In non-reactive spring application, ORM tool like Hibernate provides a way to resolve tenant and thereby make the call to appropriate database or schema. Multi-Tenancy is achieved by implementing MultiTenantConnectionProvider and CurrentTenantIdentifierResolver interfaces.

Is there a way to implement multi-tenancy using r2dbc. Is it supported as of now?
If no, what is the roadmap going forward for this feature?

[mp911de]

CurrentTenantIdentifierResolver is a resource-factory-level callback that returns a tenant-id from a parameter-less method. Typically, implementations use ThreadLocal storage to configure routing.

In Reactive Streams, we no longer can use ThreadLocal to pass items between involved components. Project Reactor introduced a custom abstract, the Subscriber Context that can be used to attach contextual values to a subscription.

Based on Context, we could provide an AbstractRoutingConnectionFactory that does the exact same as AbstractRoutingDataSource by fetching a lookup value from Context to give you the appropriate tenant-specific connection.

Do you want to have a look at AbstractRoutingDataSource and come up with a pull request?

Connection routing isn't currently on our roadmap. If we receive a pull request, then we can include that feature.

[simontb]

I think when used in conjuction with r2dbc-pool, a tenant-specific connection might not be the ideal solution depending on the implementation of tenant separation. This would make most sense when each tenant resides on his own database. When tenants are identified by schema or column, the same db connection could be used for multiple tenants.

[mp911de]

There's a vast amount of design patterns for multi-tenancy, connection/database/schema per tenant is one of them. From a consistency point of view, it makes a lot of sense to provide a routing ConnectionFactory.