在微服务中配置下游 API 端点

Question

In a microservice world, what is the recommended way of configuring the endpoint of a downstream API?

For example, if Service A needs to invoke an endpoint in Service B, we have two options:

a. Make the hostname and port number of Service B's API configurable in Service A (service-b:8080) and append the path URI in your code

or

b. Make the complete endpoint configurable in Service A (http://service-b:8080/somepath)

While I like the idea of making the endpoint configurable, it leaves a lot of room for error because the entire path needs to be specified. It also doesn't fit well when multiple endpoints need to be called from Service A to Service B which may potentially have different paths, requiring us to configure multiple endpoints.

On the other hand, option (a) seems more scalable due to above mentioned reasons.

Most search results online just demonstrated how a service can call another service and uses a hardcoded URL to demo this. It would be good to know how is the community doing this in real world projects.

PS: We use Spring Webflux and deploy to k8s.

Answer 1

I have seen mostly that teams use option a, where the serviceB "baseUrl" (which is basically https://serviceb-hostname:8080) is injected as environment property (kubernetes configmap) into the application during deployment.

The specific API specific paths are configured in application yaml or in the "proxy config" class itself as constants (eg. ServiceBProxy.java - proxy classes are those which will make rest-calls to the dependent services like service B).

Here is a portion of application yaml from one of the microservices (from one of my projects):

authorizationService:
  baseUri: ${authorizationServiceBaseUri}/api

tenantService:
  baseUri: ${tenantServiceBaseUri}/api/v1
  tenantsUri: ${tenantService.baseUri}/tenants

settingsService:
  baseUri: ${settingsServiceBaseUri}

iamService:
  fetchBatchSize: 500
  baseUri: ${iamServiceBaseUri}

Here the values of iamServiceBaseUri,settingsServiceBaseUri,tenantServiceBaseUri,authorizationServiceBaseUri are all injected during deployment. And each of them contains the clusterIP with port.