16 Multi-Tenancy

Multi-Tenancy, as it relates to software development, is when a single instance of an application is used to service multiple clients (tenants) in a way that each tenant’s data is isolated from the other.

To use the Micronaut’s multitenancy capabilities you must have the multitenancy dependency on your classpath.

implementation("io.micronaut:micronaut-multitenancy")

<dependency>
    <groupId>io.micronaut</groupId>
    <artifactId>micronaut-multitenancy</artifactId>
</dependency>

A common requirement for supporting Multi-tenancy is the ability to resolve the current tenant. Micronaut ships with the following built-in TenantResolvers:

Micronaut supports tenant propagation. As an example, take the following scenario:

You want incoming requests to the gateway microservice to resolve the tenant id via subdomain. However, you want your requests to other internal microservices to include the tenant Id as an HTTP Header.

Your configuration in the gateway microservice will look like:

micronaut:
  multitenancy:
    propagation:
      enabled: true
      service-id-regex: 'catalogue'
    tenantresolver:
      subdomain:
        enabled: true
    tenantwriter:
      httpheader:
        enabled: true

In the catalogue microservice the configuration will look like:

micronaut:
  multitenancy:
    tenantresolver:
      httpheader:
        enabled: true

To propagate the tenant you will need to write the resolved tenant ID to the outgoing requests.

Currently, Micronaut ships with two built-in implementations for TenantWriter:

16.1 Multi-Tenancy GORM

GORM supports Multi-tenancy and integrates with Micronaut.

To use Micronaut and GORM multitenancy capabilities you must have the multitenancy-gorm dependency on your classpath. For example in build.gradle:

build.gradle

compile "io.micronaut.configuration:micronaut-multitenancy-gorm"

GORM is a powerful Groovy-based data access toolkit for the JVM with implementations several data access technologies (Hibernate, Neo4j, MongoDB, GraphQL …​).

GORM supports the following different multitenancy modes:

• DATABASE - A separate database with a separate connection pool is used to store each tenants data.

• SCHEMA - The same database, but different schemas are used to store each tenants data.

• DISCRIMINATOR - The same database is used with a discriminator used to partition and isolate data.

In order to use GORM - Multitenancy you will need to configure the following properties: grails.gorm.multiTenancy.mode and grails.gorm.multiTenancy.tenantResolverClass.

Micronaut support for Multi-tenancy integrates with GORM.

The following table contains all of the TenantResolver implementations that ship with `multitenancy-gorm module and are usable out of the box.

You will need to add something like the following snippet to your app configuration:

grails:
    gorm:
        multiTenancy:
            mode: DISCRIMINATOR
            tenantResolverClass: 'io.micronaut.multitenancy.gorm.PrincipalTenantResolver'

Please, read GORM Multi-tenancy documentation to learn more.