dhall-lang
config
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dhall-lang | config | |
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113 | 32 | |
4,124 | 6,082 | |
1.3% | 0.4% | |
6.0 | 4.5 | |
26 days ago | 5 months ago | |
Dhall | Java | |
BSD 3-clause "New" or "Revised" License | Apache License 2.0 |
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dhall-lang
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Apple releases Pkl – onfiguration as code language
Fail to see how this is any different than Dhall (https://dhall-lang.org/) other than it produces plists too.
Well, Dhall provides something between JSON and a Turing complete language that can make a lot of configuration much quicker to write, if you can hack the functional syntax.
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Pkl, a Programming Language for Configuration
Kubernetes config is a decent example. I had ChatGPT generate a representative silly example -- the content doesn't matter so much as the structure:
https://gist.github.com/cstrahan/528b00cd5c3a22e3d8f057bb1a7...
Now consider 100s (if not 1000s) of such files.
I haven't given Pkl an in depth look yet, but I can say that the Industry Standard™ of "simple YAML" + string substitution (with delicate, error prone indentation -- since YAML is indentation sensitive) is easily beat by any of:
- https://nixos.org/manual/nix/stable/language/index.html
- (insert many more here, probably including Pkl)
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Why the fuck are we templating YAML? (2019)
Indeed why? However the conclusion I have is not to use JSON but to use a type safe configuration language that can express my intent much better making illegal states impossible. One example of such lang is Dhall.
Throwing in a plug for https://dhall-lang.org/
> Dhall is a programmable configuration language that you can think of as: JSON + functions + types + imports
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Is Htmx Just Another JavaScript Framework?
There are underpowered languages / tools, that can only solve a problem for which they are intended poorly. But not all limited tools are like that.
Say, eBPF is prominently not Turing-complete, which allows to guarantee that a eBPF program terminates, and even how soon. Still eBPF is hugely useful in its area.
Or, say, regular expressions are limited to regular languages; in particular, they famously [1] cannot process recursive structures, like trees. Still tools like grep / ag / rg are mightily useful.
Yes, I agree that YAML is underpowered for proper k8s configuration! But it's also too powerful for its own good in other aspects [2]. I wish Google used Dhall [3] or their own purely functional config language (FCL? I already forgot the name) instead of YAML; sadly, they did not.
[1]: https://stackoverflow.com/a/1732454/223424
[2]: https://ruudvanasseldonk.com/2023/01/11/the-yaml-document-fr...
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10 Ways for Kubernetes Declarative Configuration Management
Dhall: Dhall is a programmable configuration language that combines features like JSON, functions, types, and import capabilities. Its style leans towards functional programming, so if you're familiar with functional-style languages such as Haskell, you might find Dhall to be quite intuitive.
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Berry is a ultra-lightweight dynamically typed embedded scripting language
I've been thinking along these lines but more 'strongly validated' than statically typed in the sense that you'd be better off being able to load the entire config and then produce a list of problems (and should be able to offer good editor support if done correctly).
Though https://dhall-lang.org/ demonstrates that you can statically type quite a lot of configuration to great advantage, which appears to be programmatically embeddable in multiple languages per https://docs.dhall-lang.org/howtos/How-to-integrate-Dhall.ht...
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What Is Wrong with TOML?
I agree, I quite like https://dhall-lang.org/ for that reason. It strikes a good balance between features and being a config language.
config
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XML is better than YAML
I don‘t understand why HOCON (https://github.com/lightbend/config/blob/main/HOCON.md) isn‘t used more often (at least for configuration use cases). It‘s a superset of JSON, has comments, multiline strings, optional quotes, replacement syntax. We use it at many places, and it‘s as nice at it can get.
This is one of the few HN discussions where I feel a little bit qualified to give an opinion :)
Two years ago I started a small data quality checker software where users could define their alerts, frequencies,.. all in config files instead of modifying code.
I started with JSON as config format, but then realised comments are necessary to guide users in defining alerts. I moved to YAML, but after some "indentation incodents" started using HOCON conf [0] and never looked back. I don't see any reason for choosing YAML over one of JSON or HOCON, except being forced to. Features such as inheritance and text block support which were essential for me are nicely supported in HOCON.
- Toml-bench – Which toml package to use in Python?
- slf4j or System.Logger?
- TOML: Tom's Obvious Minimal Language
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Ron: Rusty Object Notation
HOCON is a great human-readable alternative to JSON. It's a superset of JSON with lots of cool features that make it both more readable and easier to use.
Here's a rundown of HOCON's main features: https://github.com/lightbend/config#features-of-hocon
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Spring and scala
For reading configuration files, I would probably use this: https://github.com/lightbend/config instead of Spring.
"Typesafe Config" is the library generally used to read configuration files in HOCON format, which this library introduced. It's commonly used in essentially OOP/imperative Scala contexts, including Akka and its ecosystem.
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Make systemd better for Podman with Quadlet
Interesting!
For my own servers I use an internal tool that integrates apps with systemd. You point it at the output of your build system and a config file, and it produces a deb that contains systemd unit files and which registers/starts the server on install/reboot/upgrade, as a regular debian package would. Then it uploads it to the server via sftp and installs it using apt, so dependencies are resolved. As part of the build process it can download and bundle language runtimes (I use it with a JVM), it scans native binaries to find packages that the app should depend on, and you can define your config including package metadata like dependencies and systemd units using the HOCON language [1].
Upshot is you can go from a Gradle or Maven build to a running server with a few lines of config. Oh and it can build debs from any OS, so you can push from macOS and Windows too. If your server needs to depend on e.g. Postgres, you just add that dependency in your config and it'll be up and running after the push.
It also has features to turn on DynamicUser and other sandboxing features. I think I'll experiment with socket activation next, and then bundled BorgBackup.
Net/net it's pretty nice. I haven't tried with containers because many language ecosystems don't seem to really need them for many use cases. If your build tool knows how to download your language runtime and bundle it sans container by just setting up paths correctly, then going without means you can rely on your Linux distribution to keep things up to date with security patches in the background, it means networking works as you'd expect (no accidentally opened firewall ports!) and so on. SystemD knows how to configure resource isolation/cgroups and kernel sandboxing, so if you need those you can just write that into your build config and it's done. Or not, as you wish.
With a deployment tool to automate builds/pushes, systemd to supervise processes and a big beefy dedicated machine to let you scale up, I wonder how much value the container part is really still providing if you don't need the full functionality of Kubernetes.
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Introducing JXC: An extensible, expressive data language. It's a drop-in replacement for JSON and supports type annotations, numeric suffixes, base64 strings, and more!
Other similar standards: TOML, HOCON
What are some alternatives?
cue - CUE has moved to https://github.com/cue-lang/cue
cfg4j - Modern configuration library for distributed apps written in Java.
jsonnet - Jsonnet - The data templating language
owner - Get rid of the boilerplate code in properties based configuration.
cue - The home of the CUE language! Validate and define text-based and dynamic configuration
dotenv - Loads environment variables from .env for nodejs projects.
dotenv - A twelve-factor configuration (12factor.net/config) library for Java 8+
terraform - Terraform enables you to safely and predictably create, change, and improve infrastructure. It is a source-available tool that codifies APIs into declarative configuration files that can be shared amongst team members, treated as code, edited, reviewed, and versioned.
Configur8 - Nano-library which provides the ability to define typesafe (!) configuration templates for applications.
jsonlogic - Go Lang implementation of JsonLogic
centraldogma - Highly-available version-controlled service configuration repository based on Git, ZooKeeper and HTTP/2
nix-gui - Use NixOS Without Coding