Support for dynamic Neo4j instance (Driver/URL) selection per request (multi-instance routing)

[amit-kumaryadav]

In multi-tenant architectures where each tenant is backed by a separate Neo4j instance (i.e., different URLs), there is often a need to dynamically switch the target Neo4j instance per request, based on some tenant identifier (e.g., a request header).

I’m specifically looking for support to:

• Dynamically selecting Driver per request for Repository or Neo4jClient ?

• Support repository-level multi-instance switching based on TenantContext ?

• Is there any Possibility to select DriverSelectionProvider similar to DatabaseSelectionProvider ?

[michael-simons]

Hi @amit-kumaryadav

• Selecting driver per request: Would need to be orchestrated from the web layer (Spring MVC or whatever you have) I think. The closest we have as an example is this integration test that uses multiple contexts with a driver per each. You could switch those then, I guess?
• Repository based approach: I think you can built that in your solution, we have all the means in place, but such a thing would be probably to specialised for a generic solution in this project
• Driver not, as it is also the means of transaction synchronisation. We do provide a user provider though, which would help if your tenants are different users on the same machine.

[amit-kumaryadav]

Thank you @michael-simons for the reply, As I'm using spring boot with spring data Neo4j with Repository and Neo4j client some places. is there any further documentation or implementation regarding multiple contexts ?

[meistermeier]

You could have a look at https://github.com/meistermeier/neo4j-issues-examples/tree/master/sdn-multiple-databases
As you can see, there are two configurations that contain the two drivers, neo4jTemplates, etc.:
The primary driver that gets used as the default https://github.com/meistermeier/neo4j-issues-examples/blob/master/sdn-multiple-databases/src/main/java/com/meistermeier/sdnmultipledatabases/prod/Neo4jProdConfigBean.java
Another driver talking to another instance https://github.com/meistermeier/neo4j-issues-examples/blob/master/sdn-multiple-databases/src/main/java/com/meistermeier/sdnmultipledatabases/archive/Neo4jArchiveConfigBean.java
The configurations also tell which neo4jTemplate, and with this which driver, to use for this part of the application:
https://github.com/meistermeier/neo4j-issues-examples/blob/6ad7679cb7210e07aa0d7419fee7fb08161a191f/sdn-multiple-databases/src/main/java/com/meistermeier/sdnmultipledatabases/archive/Neo4jArchiveConfigBean.java#L36C1-L36C127

In this example I created repositories for the same entity. If this is not needed, just ignore the inheritance. The important bit here is that the repositories are part of the defined packages in the different Spring configuration classes.

Side note: If you want to run this example, you might have to adjust the version of SDN and remove this bit of configuration because it is based on an older PoC https://github.com/meistermeier/neo4j-issues-examples/blob/6ad7679cb7210e07aa0d7419fee7fb08161a191f/sdn-multiple-databases/src/main/java/com/meistermeier/sdnmultipledatabases/archive/Neo4jArchiveConfigBean.java#L54

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