pinger-callbacks.js

import request from 'request';

export function pingServers(servers, onComplete) {
  let state = {
    servers,
    currentServer: 0,
    currentPingNum: 0,
    failedServers: {}
  };
  handleState(state, onComplete);
}

function handleState(state, onComplete) {
  if (state.currentServer >= state.servers.length) {
    onComplete(state.failedServers);
    return;
  }
  if (state.currentPingNum >= 3) {
    state.currentServer++;
    state.currentPingNum = 0;
    setImmediate(() => handleState(state, onComplete));
    return;
  }
  const url = state.servers[state.currentServer];
  request(url, (error, response) => {
    if (error || response.statusCode !== 200) {
      if (!state.failedServers[url]) state.failedServers[url] = 0;
      state.failedServers[url]++;
    }
    state.currentPingNum++;
    setTimeout(() => handleState(state, onComplete), 10000);
    return;
  });
}