How to Register a Spring Cloud App to Multiple Service Registries Without Startup Errors

Introduction

When using Spring Cloud to develop microservices, service registration is usually as simple as adding the registration dependency.

Why Multiple Registrations Fail

Adding two service‑registry dependencies (e.g., Nacos and Eureka) causes the application to fail at startup because the AutoServiceRegistrationAutoConfiguration class requires a single AutoServiceRegistration bean, but finds two (nacosAutoServiceRegistration and eurekaAutoServiceRegistration).

Root Cause

The failure is logged as an APPLICATION FAILED TO START error, indicating that the field autoServiceRegistration in AutoServiceRegistrationAutoConfiguration requires a single bean but two were found.

Solution: Exclude the Auto‑Configuration

Exclude

org.springframework.cloud.client.serviceregistry.AutoServiceRegistrationAutoConfiguration

via spring.autoconfigure.exclude or

@SpringBootApplication(exclude = AutoServiceRegistrationAutoConfiguration.class)

. Add the following property to application.properties:

spring.autoconfigure.exclude=org.springframework.cloud.client.serviceregistry.AutoServiceRegistrationAutoConfiguration

After exclusion, both Nacos and Eureka register successfully, as shown by the log entries confirming service registration on ports 18082.

Analysis of the init Method

The init method checks if autoServiceRegistration is null and if AutoServiceRegistrationProperties.failFast is true; if so, it throws an IllegalStateException. Since failFast defaults to false, the method normally does not abort.

Role of @Import

@Import(AutoServiceRegistrationConfiguration.class)

creates the AutoServiceRegistrationProperties bean. The configuration is conditionally loaded by @ConditionalOnProperty (property spring.cloud.service-registry.auto-registration.enabled).

Discovery Client Import Selector

The EnableDiscoveryClientImportSelector adds AutoServiceRegistrationConfiguration to the import list unless autoRegister is set to false. Therefore, keeping @EnableDiscoveryClient without disabling autoRegister ensures the registration beans are created.

Additional Considerations

If spring-boot-starter-actuator is present, you may also need to exclude ServiceRegistryAutoConfiguration to avoid another startup error.

Practical Ways to Exclude Auto‑Configurations

Use

@SpringBootApplication(exclude = SecurityAutoConfiguration.class)

for direct exclusion.

Implement an AutoConfigurationImportFilter (e.g., RegistryExcludeFilter) and register it in META-INF/spring.factories to filter out specific auto‑configurations.

Use Cases

The main scenario for multi‑registry registration is migrating services from one registry to another without downtime. The provided edas-sc-migration-starter dependency bundles the necessary configuration for easy adoption.

Conclusion

Excluding AutoServiceRegistrationAutoConfiguration (and optionally ServiceRegistryAutoConfiguration) enables a Spring Cloud application to register with multiple service registries safely, with minimal side effects.