Tommy Lee Software development for everyone else

Fixing Hot Reloads on Vagrant

One of the common issues that I’ve run into virtualizing my development environments is having to restart my server manually.

Whenever I developed locally, everything was fast, and changes appeared on first refresh. But when I used a VM, the frustration of restarting the server killed a lot of my productivity.

The Issue

Many of the hot reloads rely on detecting when the file has changed in your directory. Usually, we have something that watches the directory, and listens for a change.

Whenever a file is changed, the system kernel emits a notification letting a program know that something changed. In Linux systems, we have inotify, on OSX, it’s fsevents.

Since we’re using a virtual machine, our program is only listening to notifications emitted on the virtual machine.

Solution 1: Forward File Change Events

A recommended solution is to add a vagrant plugin to take care of forwarding file events to the VM.

Currently we’re using vagrant-fsnotify to forward events.

After installing the plugin we.

  1. add the fsnotify:true to our synced file directory.

    config.vm.synced_folder ".", "/vagrant", fsnotify: true
  2. Restart the machine

  3. Start vagrant fsnotify in a separate tab.

    vagrant fsnotify

Solution 2: Polling

An older recommendation is to switch to polling, which detects changes to the modification date occasionally. This was Ruby on Rails’ default detection method until version 4.

This is a fallback in cases where file event updates aren’t available. You can check your dev-server’s start system options, and see if a polling option exists.

I don’t recommend this, since polling takes up more memory and CPU, but if inotify forwarding is unavailable:

In this stackoverflow post, they enabled polling via vagrant rsync-auto.

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