pinger-promises.js

import _ from 'lodash';
import fetch from 'node-fetch';
import delay from 'delay';

export function pingServers(servers) {
  return _.reduce(servers, (failedServersAccumulator, url) => {
    return failedServersAccumulator.then((failedServers) => {
      return _.reduce(_.range(3), (failuresAccumulator) => {
        return failuresAccumulator.then(delay(10000)).then((failures) => {
          return fetch(url).then((response) => {
            return response.ok ? failures : failures + 1;
          });
        });
      }, Promise.resolve(0)).then((failures) => {
        if (failures > 0) failedServers[url] = failures;
        return failedServers;
      });
    });
  }, Promise.resolve({}));
}