Intro

Periodic Ping

Stand-alone node task that sends out periodic HTTP requests to keep servers awake.

• Sets up a setInterval task that will 'ping' a server (send an HTTP GET request) every so often
  • Original purpose: to keep Heroku dynos alive during certain times of day, when they might otherwise scale down
  • (Future version may allow sending pings to other URLs for various reasons)
• Takes several parameters to let you customize how it behaves
  • Set the wakeTime, sleepTime, etc (i.e. define a "time-window" within which the pings will be actually sent)
    • While the task will still continue to loop at the set interval, as long as it is OUTSIDE of the sleep/wake threshold, nothing will happen.
  • Useful for having the server get awoken only during a PART of every day, instead of around-the-clock, to better conserve resources, etc.
• Or simply pass an appName, to have the process automatically ping the Heroku app by that name, every 5 minutes.

Alternatives

• heroku-self-ping
• hubot-heroku-keepalive

Usage in your .js code

Special notes:

• App will assume standard herokuapp.com naming convention (i.e. 'abc123dummyHerokuDomainName' === http://abc123dummyHerokuDomainName.herokuapp.com)
• App will assume your Heroku server has an HTTP handler at /periodicping, and dispatch the HTTP GET request to that endpoint (this could perhaps cause 404s or other errors, if you did not create this URL).

Import package as per usual conventions:

import {ping} from 'periodic-ping';

Pre-ES6 syntax will still work:

var ping = require('periodic-ping').ping;

Base case

Call with only an appName parameter supplied:

ping({appName: "abc123dummyHerokuDomainName"});// will take the default 'frequency' variable of 300000 (every 5 minutes)
...
ping({appName: "abc123dummyHerokuDomainName", frequency: 60000});// will override the default and use the specified frequency

Advanced case

Define a config object...

const myPingConfig = {
  appName: "abc123dummyHerokuDomainName",
  wakeTime: 9,
  wakeAm: true,
  sleepTime: 5,
  sleepAm: false
};

...supply the config object when calling the package function, to enable the "time-window" feature a.k.a. set wake/sleep thresholds, between which are the only times pings will be sent out:

ping(myPingConfig); // will only ping server between 9am and 5pm

Special notes for advanced case:

• wakeTime and sleepTime may be decimal or whole number form, but must be JavaScript numbers greater than 0 and less-than or equal to 12, representing a time along a 12-hour clock.
• A.M. / P.M. options are passed in via wakeAm and sleepAm respectively, where true will correspond to A.M., and false will convert the supplied number into it's respective P.M. form