Saturday 8 April 2023

Changing where I home my source code dramatically speeds up my Windows / WSL2 / Docker environment


This is more an admission of "not initially thinking things through" on my part, but the outcome has helped me a lot, so in case there are others out there who don't think things through, maybe this will be helpful to them as well.

Or people can just point and laugh at me for being so thick.

Either way, perhaps someone will get something out of this.

My dev environment is Windows (nono, that's not the "not thinking things through" bit, just behave please). All my applications run in Docker containers, and the way I get the code into the container during dev is via a volume from my file system. For example this snippet from one of my docker-compose.yml files:

version: "3"

    # ...

            context: php
            dockerfile: Dockerfile

            - envVars.public
            - envVars.private

        stdin_open: true
        tty: true

            - ..:/var/www

I'm just using a volume there to mount my app directory as /var/www in the container.

So the source code for the app is in - say - C:\src\myApp.

When I'm building and starting my containers, I drop into a shell in WSL, navigate to /mnt/c/src/myApp/docker, and do the docker compose up from there.

On Windows 10 and with older versions of WSL2 and Docker, this worked reasonably well. The app was a bit slow, but only as much as a shrug seemed to be a reasonable reaction to it. It's only dev.

When I migrated to Windows 11 things slowed down a chunk more, and it's been getting progressively worse. I've been working on a Symfony app recently, and clearing its cache is taking about 3-4min. Clearly this is ballocks cos it's PHP and nothing is measured in minutes with PHP.

Also my rig was comparatively slower than the other bods in my team. For me the unit tests in our CFML project have gone from taking - about a year ago - 5min to run (already not great) to about 10min now. Obviously a lot of this is that the tests we inherited were not great (almost all hit the DB), and we've also been adding a lot more tests in that intervening year. Recently though I found out that for other teams members it was slow, but they were only meaning like 3min was slow. Oh I wish they only took me 3min to run.

Clearly something is wrong on this machine. It's 4yrs old, but it was reasonably high spec when I bought it, and its drive is an SSD. So: no excuses there. And it's not like I'm Bitcoin mining; I'm just doing file system operations.

Whatever it is: I need to fix it.

I concluded it was something to do with misconfiguration of Docker or WSL making file operations from my host machine being dog slow when run from the container. I googled around a bit and it seems a lot of other people have had similar problems; but various settings, registry hacks, and even disabling Windows Defender (not a viable solution long-term, but something to try) were not helping.

Then someone mentioned "when the files are in the native part of the WSL file system, not the /mnt/c partition, then the overhead of the WSL->Windows file system processing doesn't occur". Their solution was to develop the code locally, then automatically deploy it via SSH into the container.

At the same time, I read that whilst there is the /mnt/c mount inside WSL, there is also the reverse: \\wsl.localhost points to the WSL file system, specifically for me \\wsl.localhost\Ubuntu is the filesystem for the Ubuntu distro I am using.

Putting two and two together to see how close to four I could get it, I did this:

  • Got rid of my code from C: drive.
  • Instead: I checked-out my code within WSL into ~/src/myApp.
  • Ran all my docker stuff from there, in ~/src/myApp/docker.
  • In VSCode and IntelliJ, homed my projects in \\wsl.localhost\Ubuntu\home\adam\src\myApp.

When I run those tests that before took >10min to run, now they take around 50sec. That is more than an order of magnitude faster.

In my Symfony project the cache-clear now takes a few seconds. And the tests there run in a second or so too.

I realise I am perhaps inheriting some slowness in reverse by accessing \\wsl.localhost\Ubuntu from Windows, but I am only dealing with occasional file edits and such like. Speed there is not a problem. Not one I could perceive anyhow.

I wish I had sat down to sort this out a few months back now. I had aimlessly googled in the past for 10min or so trying to find an easy silver bullet, but never found it and each time I looked I saw the same stuff. Today I rolled up my sleeves and said "right, I'm fixing this", and after about an extra 45min of googling and trying stuff (and then backing-out each thing that didn't work again), I landed on the solution.