How to create a self-updating Node.js application?

Question

I'd like to create an application with Node.js that periodically checks for updates and installs them if there are any.

The basic components are clear to me:

• A web server (or an FTP server, a file system, ...) which contains the update packages
• A version system (such as SemVer) so that you can tell which package is newer
• A public-key algorithm for signing update packages

Then, there may be different strategies on when to check for updates and install updates:

• On application start
• On application end
• When idleing

The application may even be shut down hard and restarted automatically.

But there are some questions left:

• Is there any module on npm available that already provides such a system?
• How to organize the different versions in the file system? Basically you'd have a host and multiple (versioned) cores. Should there be one data folder for all of them?
• How to deal with npm install & co. for newly downloaded packages?
• How to deal with broken updates?
• How could you implement such a thing so that it's compatible to Heroku & co. where you don't have a permanent drive that you can drive to?

In general: How would you try to achieve a system like this?

Answer 1

First, you could use NPM itself for package and app delivery. Second, you could add a script file to add a cron job in the package.json file (e.g. 'postinstall' or 'update') for a periodic update process. In this script you could check all you need like broken updates. In Heroku you can use a Scheduler Worker for update processing.