Watchpuppy 🐶

An almost fully grown watchdog for node.js

This is a simple watchdog for node.js. It has no external dependencies and runs within the node process itself. This is not meant to replace something like an external health check service or a more advanced tool like foreverjs.

But sometimes you just need to keep an eye out on a simple worker script and make sure it is stil crunching data.

It is kept simple, i.e. there are no dependencies, just plain simple JavaScript (ES6).

Pull requests welcome.

Install

npm install watchpuppy

Usage

Simple example checking every 5 minutes and exiting the process if there weren't at least two pings:

const Watchpuppy = require('watchpuppy');

//setup watchpuppy

//defaults:
// checkInterval: 10000 (10s)
// minPing: 1
// stopOnError: true (stop the watchpuppy when a check fails)

//example:
// check every 5 minutes (checkInterval in ms)
// require at least two pings in the 5 min window
// stop checking after first error
// exit process on error

const options = {checkInterval: 5 * 60 * 1000, minPing: 1, stopOnError: true};
const callback = (err) => {
  console.error(err);
  process.exit(1);
};

const watchpuppy = new Watchpuppy(options, callback);

//fire a ping whenever you know things are running fine, e.g. somewhere in your stream processing
watchpuppy.ping();

//you can modify the weight of a ping by passing in a number
watchpuppy.ping(5); //equivalent to firing watchpuppy.ping() five times

//you can also invalidate a ping by passing in a negative number
watchpuppy.ping(-1); //doesn't do anything

Another example that doesn't stop on the first failure and simply logs errors to the console:

const Watchpuppy = require('watchpuppy');

const options = {stopOnError: false, minPing: 5};
const callback = (err) => {
  //err is a js Error with a message such as: 'only 3 pings received since last check'
  console.log(err.message);
};

const watchpuppy = new Watchpuppy(options, callback);

License

This module is licensed under the MIT license.