Zephyr/Zodiac

A pair of Springboot services demonstrating Hashi Corp.'s Consul. Consul is a set of tools that enable services to be run in a _service mesh, allowing for flexible and scalable operations.

The example focuses on three of those features, using the Springboot 'cloud' framework:

• Service registration and discovery
• Health monitoring
• Distribution/dynamic configuration

Not discussed here, but important ingredients of a full service mesh implementation:

• Secure proxys, service talk http to proxy (sidecar) which translates to TLS for inter-service comms
• Multi DCs: transparently communication between not just nodes, but also datacenters

Example Architecture

Two services are deployed in the example, one of which (zodiac-service) relies on an api exposed by the second (zephyr-service). When a call is made to zodiac-service's API, it satisfies it by finding a URL for zephyr-service and calling the endpoint.

For convenience, zodiac-service runs on a fixed localhost port, 8080, while zephyr-service has random port assigned when started.

Both services leverages the Springboot cloud framework to register themselves, and discover other services. They also provide endpoints that are utilized by Consul's health checker and proxy algorithms.

Additionally, zephyr-service uses Consul KV store to access configuration data dynamically to satisfy the API call.

 consul agent -dev

 curl localhost:8500/v1/agent/services

 curl localhost:8500/v1/agent/checks

 consul kv put

 curl localhost:8500/v1/agent/checks

curl --request PUT --data 'America/Los_Angeles' localhost:8500/v1/kv/config/zephyr-service/service/timezone

curl localhost:8500/v1/kv/zephyr-service

Distributed Configuration

With the Zephyr service started, use either the consul CLI, it's HTTP interface, or via the consul agent web page (e.g, http://localhost:8500/ui/dc1/services) to set key /config/zephyr-service/zephyr/response to the required value.

This will override the default value from resources/zephyr-application.yml:

service:
  timezone: 'America/Los_Angeles'

forcing the service's APi controller to be reloaded, with the new value:

@RestController
@RefreshScope
public class ApiController {

    @Value("${service.timezone}")
    private String value;

    @GetMapping("/call")
    public String call() {
        return value;
    }
}