Split large traffic into pieces, so there will no more server down :)

splitTraffic.js

function splitTraffic() {
    const origServerList = [
        'server1',
        'server2',
        'server3',
        'server4',
    ];
    const serverCount = origServerList.length;
    const firstServer = origServerList[Math.floor(Math.random() * serverCount)];
    let modServerList = origServerList.filter(serv => serv !== firstServer);
    modServerList.unshift(firstServer);
    return modServerList;
}

/* CODE BELOW FOR TEST USE */

let [totalTraffic, serv1, serv2, serv3, serv4, x] = [1400, 0, 0, 0, 0, 0];

for (let i = 0; i < totalTraffic; i++) {
    x = splitTraffic()[0];
    switch (x) {
        case 'server1':
            serv1++;
            break;
        case 'server2':
            serv2++;
            break;
        case 'server3':
            serv3++
            break;
        case 'server4':
            serv4++;
            break;
        default:
            break;
    }
}

serv1 = serv1 / totalTraffic * 100;
serv2 = serv2 / totalTraffic * 100;
serv3 = serv3 / totalTraffic * 100;
serv4 = serv4 / totalTraffic * 100;
let totalHit = serv1 + serv2 + serv3 + serv4;

console.log(
    `server1 hit: ${serv1}%`,
    `server2 hit: ${serv2}%`,
    `server3 hit: ${serv3}%`,
    `server4 hit: ${serv4}%`,
    `total hit: ${totalHit}%`
);