Development Trick: Auto-updating & Auto-reloading

For the upgrade of JS Bin to version 3 (an open beta), the whole code base is in the process of being rewritten to run as a Node.js process (whilst still working as a PHP application).

What’s neat is I’ve got it to automatically pull the latest changes from github and automatically restart my Node process.

I don’t claim this to be particularly clever, and I’m sure I should be able to trigger a pull on the server as a push happens, but this works fairly well for my development workflow (where the app needs to be online) and is pretty simple – which I like.

Commands

For those like me who don’t care about the detail, here’s exactly what I’m doing in the terminal:

$ cd /WWW/jsbin/
$ screen -S gitpull
$ watch git pull
CTRL+a d
$ screen -S jsbin
$ nodemon .
CTRL+a d

Here’s what’s going on.

Screen

I’m using a linux process called screen which simply put: creates a persistent shell that you can send to the background and retrieve at a later date. This means I can run my processes inside a screen and get them back any time I want if there’s some debugging to do.

Now I’ve got a way of managing two tasks:

1. Pull from github for any changes
2. Restart my node process

Once you’re inside screen to detach (and return to your original shell) you use the command sequence CTRL+a d.

Here’s a few extra simple commands:

• screen -ls will show all the screen processes you’re running and the PIDs they have. You’ll need the PID to reattach the screen
• screen -r<PID> so in my case: screen -r gitpull will reattach and put me back in to the screen

Auto-updating code

Inside one screen we make use of watch which will keep running a process every 2 seconds. So I “watch” the git pull command.

Obviously this is a bit crap because it’s trying to pull from github to no avail most of the time, but it does mean that when I push new code up, this process will automatically pull.

Which leads me on to restarting…

Auto-reloading

In another screen I’m running the development tool Nodemon to auto restart when any JavaScript files change (which come from the git pull).

So that’s it. Pretty simple.