feat: simple round-robin solution for load-balancing

Signed-off-by: kvmw <[email protected]>

Author: kvmw

packages/greeter/server.js

@@ -4,7 +4,10 @@ import { env, eureka } from '@greeting/shared';
 const app = express();
 const eurekaClient = await eureka.getClient(env.port);
 
-const serviceHost = () => {
+// Counter for round-robin load balancing
+let instanceCounter = 0;
+
+const getServiceInstance = () => {
   const instances =
     eurekaClient
       .getInstancesByAppId('GREETER-MESSAGES')
@@ -14,14 +17,17 @@ const serviceHost = () => {
     throw new Error('No instances of GREETER-MESSAGES available');
   }
 
-  return instances[0].hostName;
+  const selectedInstance = instances[instanceCounter % instances.length];
+  instanceCounter = (instanceCounter + 1) % instances.length;
+
+  return selectedInstance.hostName;
 };
 
 app.get('/hello', async (req, res) => {
   const salutation = req.query.salutation || 'Hello';
   const name = req.query.name || 'Bob';
 
-  const url = `https://${serviceHost()}/greeting?salutation=${salutation}&name=${name}`;
+  const url = `https://${getServiceInstance()}/greeting?salutation=${salutation}&name=${name}`;
 
   const response = await fetch(`${url}`, {
     headers: {