Looking up services
Using Load-balancer
Spring Cloud has support for Feign (a REST client builder) and also Spring RestTemplate
for looking up services using the logical service names/ids instead of physical URLs. Both Feign and the discovery-aware RestTemplate utilize Ribbon for client-side load balancing.
If you want to access service STORES using the RestTemplate simply declare:
@LoadBalanced @Bean public RestTemplate loadbalancedRestTemplate() { return new RestTemplate(); }
and use it like this (notice how we use the STORES service name/id from Consul instead of a fully qualified domainname):
@Autowired RestTemplate restTemplate; public String getFirstProduct() { return this.restTemplate.getForObject("https://STORES/products/1", String.class); }
If you have Consul clusters in multiple datacenters and you want to access a service in another datacenter a service name/id alone is not enough. In that case
you use property spring.cloud.consul.discovery.datacenters.STORES=dc-west
where STORES
is the service name/id and dc-west
is the datacenter
where the STORES service lives.
Spring Cloud now also offers support for Spring Cloud LoadBalancer. |
As Spring Cloud Ribbon is now under maintenance, we suggest you set spring.cloud.loadbalancer.ribbon.enabled
to false
, so that BlockingLoadBalancerClient
is used instead of RibbonLoadBalancerClient
.
Using the DiscoveryClient
You can also use the org.springframework.cloud.client.discovery.DiscoveryClient
which provides a simple API for discovery clients that is not specific to Netflix, e.g.
@Autowired private DiscoveryClient discoveryClient; public String serviceUrl() { List<ServiceInstance> list = discoveryClient.getInstances("STORES"); if (list != null && list.size() > 0 ) { return list.get(0).getUri(); } return null; }