Some folks on the internet were interested in how I had managed to ditch Docker for local development. This is a slightly overdue write up on how I typically do things now with Nix, Overmind and Just.
You can have my Docker development environment when you pry it from my cold dead hands!
And keep it that way! We need people on both sides to further spur progress. Plus I’m jealous cause I still don’t have a firm grasp on docker.
I wish he had written why he’s so anti-container/docker. That’s a pretty unusual stance I haven’t been exposed to yet.
Hi!
First I’d like to clarify that I’m not “anti-container/Docker”. 😅
There is a lot of discussion on this article (with my comments!) going on over at Tildes. I don’t wanna copy-paste everything from there, but I’ll share the first main response I gave to someone who had very similar feedback to kick-start some discussion on those points here as well:
Some high level points on the “why”:
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Reproducibility: Docker builds are not reproducible, and especially in a company with more than a handful of developers, it’s nice not to have to worry about a
docker buildcommand in the on-boarding docs failing inexplicably (from the POV of the regular joe developer) from one day to the next -
Cost: Docker licenses for most companies now cost $9/user/month (minimum of 5 seats required) - this is very steep for something that doesn’t guarantee reproducibility and has poor performance to boot (see below)
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Performance: Docker performance on macOS (and Windows), especially storage mount performance remains poor; this is even more acutely felt when working with languages like Node where the dependencies are file-count heavy. Sure, you could just issue everyone Linux laptops, but these days hiring is hard enough without shooting yourself in the foot by not providing a recent MBP to new devs by default
I think it’s also worth drawing a line between containers as a local development tool and containers as a deployment artifact, as the above points don’t really apply to the latter.
If your dev documentation includes your devs running docker build, you’re doing docker wrong.
The whole point is that you can build a working container image and then ship it to a registry (including private registries) so that your other developers/users/etc don’t have to build them and can just run the existing image.
Then for development, you simply use a bind mount to ensure your local copy of the code is available in the container instead of the copy the container was built with.
That doesn’t solve the performance issues on Windows and Mac, but it does prevent the “my environment is broke” issues that docker is designed to solve
The whole point is that you can build a working container image and then ship it to a registry (including private registries) so that your other developers/users/etc don’t have to build them and can just run the existing image.
Agreed, we still do this in the areas where we use Docker at day job.
I think the mileage with this approach can vary depending on the languages in use and the velocity of feature iteration (ie. if the company is still tweaking product-market fit, pivoting to a new vertical, etc.).
I’ve lost count of the number of times where a team decides they need to npm install something with a heavy node-gyp step to build native modules which require yet another obscure system dependency that is not in the base layer. 😅
Cost: Docker licenses for most companies now cost $9/user/month
Are you talking about Docker Desktop and/or Docker Hub? Because plain old docker is free and open source, unless I missed something bug. Personally I’ve never had much use for Docker Desktop and I use GitLab so I have no reason to use Docker Hub.
I believe this is the Docker Desktop license pricing.
On an individual scale and even some smaller startup scales, things are a little bit different (you qualify for the free tier, everyone you work with is able to debug off-the-beaten-path Docker errors, knowledge about fixes is quick and easy to disseminate, etc.), but the context of this article and the thread on Mastodon that spawned it was a “unicorn” company with an engineering org comprised of hundreds of developers.
Docker builds are not reproducible
What makes you say that?
My team relies on Docker because it is reproducible…
Highly recommended viewing if you’d like to learn more about the limits of reproducibility in the Docker ecosystem.
You might be interested in this article that compares nix and docker. It explains why docker builds are not considered reproducible:
For example, a Dockerfile will run something like apt-get-update as one of the first steps. Resources are accessible over the network at build time, and these resources can change between docker build commands. There is no notion of immutability when it comes to source.
and why nix builds are reproducible a lot of the time:
Builds can be fully reproducible. Resources are only available over the network if a checksum is provided to identify what the resource is. All of a package’s build time dependencies can be captured through a Nix expression, so the same steps and inputs (down to libc, gcc, etc.) can be repeated.
Containerization has other advantages though (security) and you can actually use nix’s reproducible builds in combination with (docker) containers.
Appreciate the in-depth response! I’ve always been interested in Nix but I’m scared of change lol. And I’m a single systems administrator on a team of mostly non-technicals so large changes like that are … less necessary. Plus you know, mostly dealing with enterprise software on windows unfortunately. One of these days.
NixOS on WSL2 is actually my development environment of choice these days! (With my tiling window manager komorebi, of course! 😀)
Docker performance on macOS (and Windows), especially storage mount performance remains poor
I remember when I first got a work Macbook and was confused why I had to install some ‘Docker Desktop’ crap.
I also learnt how much Docker images care about the silicon they’re built on… Fucking M1 chip can be a pain…
Docker is like, my favorite utility tool, for both deployment AND development (my replacement for Python virtual environments). I wanted to hear more of why I shouldn’t use it also.
Right? If it’s about ease of insight into containers for debugging and troubleshooting, I can kinda see that. Although I’m so used to working with containers it isn’t a barrier really to me anymore.
@astral_avocado @LGUG2Z That definitely would’ve been helpful for readers new to the Nix scene, but I don’t think that’s the purpose of this article. It’s written as more of an example of a way to move to Nix, rather than an opinion piece on why you should move away from Docker.
I won’t try to argue why you should switch. However, I would recommend you look into the subject more, Docker is a great tool, but Nix is on a diffeeent level 🙃
I’m anti everything that requires daily use of arcane command line bullshit. I thought we were on the way to being over that when Windows 3.1 came out.
If it needs to be done more than once, make it a button on a little program. I’ve rolled my own for any of them that can be triggered from the windows command line. But Docker and others that require their own unique command line I can’t do that. I wouldn’t be as annoyed by Docker if Docker Desktop just did all the crap it should instead of requiring command line bullshit every damn day.
I mean… all those buttons are essentially just calling a command line in the end. And coding that button takes more work so command line is always going to be more likely to be your only option. If you find commands arcane then that’s probably an argument that the help docs should be clearer or the commands themselves should be clearer.
Making a little program that opens a window with some buttons to pin to my taskbar is infinitely easier than digging out docs and copy pasting into a command line every time I need to do anything. Paste the command once, done. It’s like 10 lines of code, plus about 3-4 for each command I add. Maybe drag the window a bit bigger when I add the button.
Kind of cool if your production infrastructure can match. But for most companies (ie, Fortune 500 and some medium companies) implementing this would need a force majeure.
Decades of software rot, change in management, change in architecture, waxing and waning of software and hardware trends, half assed implementations, and good ole bottom tier software consultation/contractors brought into the mix make such things impossible to implement at scale.
Once worked at a company where their onprem infra was a mix of mainframe, ibm / dell proprietary crap, Oracle vendor locked, and some rhel/centos servers. Of course some servers were on different versions of the OS. So it was impossible to setup a development environment to replicate issues.
For the most part, that’s why I still use docker for most jobs. Much easier to pull in the right image, configure app deployment declaratively, and reproduce the bug(s). I would say 90% of the time it was reproducible. Before docker/containerization it was much less than that and we had to reproduce in some non production environment that was shared amongst team.
I use a similar approach, but I went further by creating a system that compose like docker-compose would. The trick was to write my own nix function mergeShells.
https://her.esy.fun/posts/0024-replace-docker-compose-with-nix-shell/index.html
For now, I am pretty happy with it. Also, I put the init script inside nix-shell and not in external files and use exit signal to cleanup the state.
Related, this article talks about combining nix and direnv: https://determinate.systems/posts/nix-direnv
Using these tools you are able to load a reproducible environment (defined in a nix flake) by simply cding into a directory.
