service-discovery-devops

Registering a Service with DNS Resolution and Consumer Notification

When a new service instance comes up, it needs to register, pass a health check, get added to routing, and notify downstream consumers -- all before traffic arrives. This workflow registers the service with real DNS resolution via InetAddress.getAllByName, health-checks the endpoint, updates routing rules (writing to a local file), and notifies consumers with their resolved addresses.

Workflow

serviceName, endpoint, version, healthCheckUrl
                   |
                   v
+----------------+     +-------------------+     +----------------------+     +------------------------+
| sd_register    | --> | sd_health_check   | --> | sd_update_routing    | --> | sd_notify_consumers    |
+----------------+     +-------------------+     +----------------------+     +------------------------+
  registrationId        DNS resolution of         routing file written        consumer DNS resolved
  + DNS resolved        health endpoint           active instances counted    notification sent
  addresses

Workers

RegisterWorker -- Registers serviceName at endpoint with version. Performs real DNS resolution via InetAddress.getAllByName on the endpoint hostname. Returns registrationId, resolvedAddresses, and dnsResolved flag.

HealthCheckWorker -- Resolves the health check endpoint's DNS and validates the service. Returns the endpoint, serviceName, version, and resolvedAddress.

UpdateRoutingWorker -- Updates routing for the service: resolves the endpoint address, checks port reachability, counts active instances, and writes a routing file to disk. Returns updated: true.

NotifyConsumersWorker -- Notifies downstream consumers about the service availability update. Resolves each consumer's DNS and marks them as notified.

Tests

30 unit tests cover registration, health checks, routing updates, and consumer notification.

Running

See ../../RUNNING.md for setup and execution instructions.