Spring Boot: Handle configuration in multitenant application

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I am implementing a Spring Boot application which will be providing a multitenant environment. That is achieved in my case by using a database schema for each customer. Example see this project.

Now I am wondering how to implement tenant-specific configurations. I am using @ConfigurationProperties to bundle my property values, but these are getting instantiated once and not for each tenant.

What if I would like to use Spring Cloud Config with multiple tenant specific git repository as an configuration backend. Would it be possible when using a jdbc backend for Spring Cloud Config?

Is there any way with default Spring mechanisms or do I have to implement a database based configuration framework myself?

Edit: For example I have two tenants called Tenant1 and Tenant2. Both are running over the same application in the same context and are writing in the database schemes tenant_1 and tenant_2.

Identification of tenants is happening over keycloak (see Spring Keycloak multi tenant example). So I identify the tenantId from the jwt token and select the database connection like described here.

But now I would need the same mechanism for @Configuration beans. Since @Configuration beans are as far as I know Singletons, so there is always ONE configuration per application scope, and not ONE configuration per tenant.

So using Spring Cloud Config Tenant1 is using https://git-url/tenant1, Tenant2 is using Hashicorp Vault as backend and perhaps Tenant3 will be using a jdbc based configuration backend. And all of that in ONE (of course scalable) application.

spring-cloud-config spring-boot multi-tenant spring
2 Answers

You can use Spring Cloud Config for your scenario and it is adoptable. It is easily configurable and provides out of the box features. For your specific scenario, you can have any number of microservices running yet all controlled by one Spring Cloud Config Server which is connected to one Git Repository. Your all microservices are asking configuration properties from Spring Cloud Config Server and it is directly fetching properties from Git Repository. That repository can have multiple property files. It can hold common properties for all the microservices or specific service based configuration properties. If you want to keep confidential properties more securely, that is also made possible via HashiCorp vault. I will leave an image below for you to get a better idea about this concept.

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In the below image, you can see the Git Repository with common configuration property files and specific configuration property files for different services yet in same repository.

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I will add another image for you to get a better idea how does this can be arranged with application profiles as well.

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Finally I will add something additional to show the power of Spring Cloud Config and out of the box features it allows us to play with. You can automatically refresh configuration properties in running application as well. You can configure Spring Cloud Config to do that. I will add an architectural diagram to achieve that.

enter image description here

References for this answer is taken from Spring in Action, Fifth Edition Craig Walls

user_72188810

In case your application uses tenant specific files (html templates etc), the following can be applied. As I have used the below approach for handling many tenants and works fine and easy to maintain.

I would suggest that you maintain a consistent configuration source (JDBC) for all of your tenant configurations. This helps you have a single source that is cacheable and scalable for your application. Also, you could have your tenants navigate to a configuration page to manage their settings and alter them to suit their needs at any point of time on the fly. (Example Settings: Records Per Page, Theme, Logo, Filters etc...)

Having the tenant configuration in files in git will be a difficult task when you wanted to auto-provision tenant's when they sign-up as it will involve couple of distributed services. Having them in a TenantSettings table with the tenantId as a column could help you get the data in no time and will be easy.

user_5419170
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