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Use a simple round robin to select instances #2

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Merged
kvmw merged 1 commit into from
Jul 21, 2025
Merged

Use a simple round robin to select instances #2

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29 changes: 24 additions & 5 deletions packages/greeter/server.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2,18 +2,37 @@ import axios from 'axios';
import express from 'express';
import { env, eureka } from '@greeting/shared';

class SimpleRoundRobin {
constructor(eurekaClient) {
this.eurekaClient = eurekaClient;
this.index = 0;
}

next() {
const instances =
this.eurekaClient
.getInstancesByAppId('GREETER-MESSAGES')
?.filter((instance) => instance.status === 'UP') || [];

if (instances.length === 0) {
return new Error('No instances of GREETER-MESSAGES available');
}
this.index = this.index % instances.length;
const instance = instances[this.index];
this.index++;
return instance.hostName;
}
}

const app = express();
const eurekaClient = await eureka.getClient(env.port);

const lookupService = () => {
return eurekaClient.getInstancesByAppId('GREETER-MESSAGES')[0]?.hostName;
};
const selector = new SimpleRoundRobin(eurekaClient);

app.get('/hello', async (req, res) => {
const salutation = req.query.salutation || 'Hello';
const name = req.query.name || 'Bob';

const url = `https://${lookupService()}/greeting?salutation=${salutation}&name=${name}`;
const url = `https://${selector.next()}/greeting?salutation=${salutation}&name=${name}`;

const response = await axios.get(`${url}`, {
headers: {
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4 changes: 4 additions & 0 deletions packages/shared/src/eureka.js
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,10 @@ const getClient = async (port) => {
$: port,
'@enabled': true,
},
securePort: {
$: port,
'@enabled': true,
},
vipAddress: 'UNKNOWN',
dataCenterInfo: {
'@class': 'com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo',
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