services-flake/doc/start.md
Shivaraj B H 1ae2579853
docs: add motivation for creating services-flake (#125)
resolves #124 and #123

---------

Co-authored-by: Sridhar Ratnakumar <3998+srid@users.noreply.github.com>
2024-03-07 22:10:16 +05:30

65 lines
2.4 KiB
Markdown

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# Getting started
## New project
Use the [template flake](https://github.com/juspay/services-flake/blob/main/example/flake.nix) provided by `services-flake`:
```sh
mkdir example && cd ./example
nix flake init -t github:juspay/services-flake
nix run
```
## Existing project
services-flake uses [process-compose-flake](https://community.flake.parts/process-compose-flake) to manage the services. Let's first import the `flake-parts` modules provided by `process-compose-flake` and `services-flake` in your flake:
```nix
{
inputs.process-compose-flake.url = "github:Platonic-Systems/process-compose-flake";
inputs.services-flake.url = "github:juspay/services-flake";
...
outputs = inputs:
inputs.flake-parts.lib.mkFlake { inherit inputs; } {
imports = [
inputs.process-compose-flake.flakeModule
];
perSystem = { ... }: {
process-compose."default" = {
imports = [
inputs.services-flake.processComposeModules.default
];
};
}
};
}
```
As an example, let's add the `redis` service to your flake:
```nix
# Inside `perSystem.process-compose.default`
{
services.redis."r1".enable = true;
}
```
Time to run the service:
```sh
nix run
```
## Under the hood
- The `services-flake` module configures [process settings](https://community.flake.parts/process-compose-flake#usage) for a service. In simple terms, it handles stuff like health checks, restart policies, setup scripts, etc. by using the easy to configure APIs provided by `process-compose-flake`.
- The `process-compose-flake` module uses these settings to generate `packages.${system}.default`[^how-default] (`nix run` above, runs this package by default), which runs [process-compose](https://github.com/F1bonacc1/process-compose) with the generated YAML configuration[^sample-config].
[^how-default]: `default` is the name of the process group that is derived from `process-compose.<name>` in `perSystem.process-compose`.
[^sample-config]: See the example configuration from the [getting started](https://f1bonacc1.github.io/process-compose/intro/) section of the process-compose docs.
## Examples
- In [Nammayatri](https://github.com/nammayatri/nammayatri), services-flakes is used to run the local services stack (which used to be run with docker-compose). Read about it [in this blog post](https://nixos.asia/en/blog/replacing-docker-compose).