Provide Spring gRPC DiscoveryClient integration #1675

Description

spring-projects/spring-grpc issue #341 requested support for resolving gRPC client targets such as discovery:///service-name through Spring Cloud DiscoveryClient.

A working prototype was implemented in spring-grpc, but Spring gRPC maintainers noted that this integration should live on the Spring Cloud side because of the dependency direction between Spring Boot, Spring gRPC and Spring Cloud:

• Support Spring Cloud Discovery for NameResolver/NameResolverProvider spring-projects/spring-grpc#341 (comment)

Proposed Scope

Add a Spring Cloud module that bridges Spring Cloud service discovery with Spring gRPC by:

• resolving discovery:///service-name targets through DiscoveryClient
• refreshing resolved addresses when Spring Cloud publishes a HeartbeatEvent
• preferring the gRPC_port metadata entry and falling back to the regular service instance port
• optionally publishing spring.grpc.server.port as gRPC_port metadata through the Registration abstraction when metadata is mutable

Why This Belongs Here

The implementation depends on Spring Cloud abstractions such as:

• DiscoveryClient
• HeartbeatEvent
• Registration

while the gRPC side can stay limited to Spring gRPC extension points.

Prior Art / Prototype

The current prototype and discussion live here:

• Spring gRPC issue: Support Spring Cloud Discovery for NameResolver/NameResolverProvider spring-projects/spring-grpc#341
• Spring gRPC PR: Add Spring Cloud discovery name resolver support spring-projects/spring-grpc#394

Question

Would Spring Cloud Commons accept this as:

1. a new module in this repository, or
2. a different Spring Cloud repository / subproject?

If this repository is acceptable, I can adapt the current prototype to match Spring Cloud Commons conventions and open a PR here.