Playing with Docker on Windows 10 with Live Reload (nodemon)

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I know. I know. I’m a bit late to the game – and this was long overdue…

For a few years now, I’ve been fully submerged in the world of Enterprise Angular development – which has unfortunately led to me falling behind on some technologies, such as Docker. While I’ve been aware of LXCs for many, many years now, I’d not gotten past 101 setup tutorials for Docker to date – which changes today.

This post details my initial journey with running my first Docker container based Node.js application under Windows 10 – as well as the challenges encountered with live reload via nodemon during the journey, and how I got everything working well enough in the end.

As is often the case, I went looking for a recent basic getting started writeup, which led me to Dinushanka Ramawickrama’s “Let’s Dockerize a Nodejs Express API“. Being a huge fan of Node.js, often choosing it as my stack of preference, this seemed like a great place to start – taking a Node Express API and shoving it into a container using Docker.

All in all, I have to say that Dinushanka’s write up is pretty good – short, to the point, easy to follow, and accurate. It wasn’t until getting the last section, titled “Dynamically Change the Contents of the Running Container using Nodemon.”, that I ran into problems – for the life of me, I could not get live reload via nodemon to work as expected. Docker would output log messages seemingly indicating that all was well, but when I’d make changes to my server they weren’t syncing in my Docker container.

nodemon reporting for duty – but the duty never shows

As I often do in situations like this, I turned to the comments – assuming that someone else had already experienced my pain and provided me a nicely packaged solution. Nope – not this time. So I went searching, which led me to a relatively recent issue on nodemon’s github repo:
https://github.com/remy/nodemon/issues/1447 . As suggested by a commenter, I checked out “Application isn’t restarting” in the nodemon readme –
https://github.com/remy/nodemon#application-isnt-restarting . Going for the low hanging fruit approach, I updated my package.json’s dev script to include the Legacy Watch flag:


Now, all that was left was to rebuild my image and rerun it:

> docker-compose down
> docker-compose build
> docker-compose up

With the above in place, all was well in the world – containerized live reloading node development. AIN’T LIFE GRAND?!

Long story short, essentially the mechanisms leveraged on Linux systems to detect filesystem changes aren’t available in Windows – and so live reload doesn’t work out of the box. Fortunately, nodemon’s Legacy Watch uses a different (though more costly) polling mechanism to detect changes – which works fine for our purposes of ‘getting started’. Note: this is actually a known issue, as you can see in the Docker official docs:
https://docs.docker.com/docker-for-windows/troubleshoot/#inotify-on-shared-drives-does-not-work

It’s worth mentioning that some folks have reported this issue when developing on host Linux systems, which is believed to be related to inotify-tools not being present in the OS image used to create your container. In these cases, your nodemon woes may be solved by simply updating your Dockerfile with an additional run statement to install the package using the container OS’ package manager. See here:
https://stackoverflow.com/questions/42445288/enabling-webpack-hot-reload-in-a-docker-application/46804953#46804953

-Matt

Installing Node.js in the Ubuntu Windows Linux Subsystem

Installing Node.js in the Windows Linux Subsystem (WLS) is quick and easy – accomplished by essentially running 2 commands. By reading the official Node.js docs, we can see that Ubuntu installs are provided via NodeSource. Once at NodeSource, we see the commands required for Debian based Linux systems, such as Ubuntu (as of the time of this writing, I am running the Ubuntu 18.04.01 LTS subsystem).

First, we need to pull down the installer script and execute it using a 1-liner:

curl -sL https://deb.nodesource.com/setup_11.x | sudo -E bash -

A bit about the command that we just ran. As you’re likely already aware, curl is a command line utility for interfacing with various protocols – in this case, http(s). If so inclined, you can take a look at the contents of the “setup_11.x” bash script. So, as you know, we’re working with a bash script – which we’re pulling down with the assistance of curl, but rather than saving it to our local filesystem, we’re piping it’s contents to bash, which we’re elevating using sudo. As you may have noticed, we’re actually calling “sudo -E”, which instructs sudo to preserve environmental variables while executing. So we call “bash -” as administrator, that training dash instructing bash “take the input from the pipe and treat the contents of a bash script”. By inspecting the output, or better yet from reading the bash script, we can see that we’re essentially modifying our apt sources to allow us to ‘apt install’ Node.js using the NodeSource repo. Easy peasy.

sudo apt-get install -y nodejs

With our apt sources updated to include the NodeSource repo, we use “apt-get install” to install nodejs – just as we would any apt package. Just as is the case with other apt installed packages, apt will evaluate all required dependencies for Node.js and install them on your system as needed before installing the Node.js binary.

Once installation has completed, you should be able to execute “node -v” and “npm -v” to see your installed versions.

We now have a fully functional Node.js environment in our Windows Linux Subsystem!