nixops4-quick-intro/slides.md

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NixOps4

• Why
• What
• How

Robert Hensing @roberth

fediversity.eu

@roberth

Robert Hensing

• Hercules CI
• Nix Steering Committee
• Nix team
• Module System / flake-parts / modular services / single package fixpoint
• NixOps4

Fediversity.eu

• NLNet
• NORDUnet
• Tweag
• Open Internet Discourse Foundation

Fediversity.eu

Quotes, emphasis mine:

The Fediversity Project is a comprehensive effort to bring easy-to-use, hosted cloud services that have service portability and personal freedom at their core to everyone.

The Fediversity Project enables easy hosting for a wide variety of fediverse platforms, all based on NixOS.

helps with decentralisation of the internet, a core principle of the NGI, by making it easier for people to participate in the Open Social Web on their own terms.

NixOps4

• Deployment tool
• WIP
• Successor to NixOps

Why

2013 - 2020

• NixOps 1 is a tool to deploy NixOS systems
• Provisioning, secrets
• Also resources, e.g. AWS Route53

Why

• Testing and CI
• Python (*)
• Call Nix evaluator in batch, twice (bad)

Why

NixOps 2

2020 - ...

• Plugins
• Polyrepo

Why

NixOps 2

2020 - ...

Why

2021

@roberth

• Still the only tool that integrates provisioning

Step back

Nix

┌────────────┐                      ┌────────────────────┐
│ Nix        │---- instantiate ---->│ Derivations        │ ↺ store path
│ expression │                      └────────────────────┘
│ language   │                                ⇑ builds
│            │                      ┌────────────────────┐
│            │                      │ Nix sandbox, store │
└────────────┘                      └────────────────────┘

Architecture

NixOps4

┌────────────┐                      ┌────────────────────┐
│ Nix        │---- configure ------>│ Resources          │ ↺ nix value
│ expression │                      └────────────────────┘
│ language   │                                ⇑ run output
│            │                      ┌────────────────────┐
│            │---- instantiate ---->│ Derivations        │ ↺ store path
│            │                      └────────────────────┘
│            │                                ⇑ builds
│            │                      ┌────────────────────┐
│            │                      │ Nix sandbox, store │
└────────────┘                      └────────────────────┘

Resource

• Declares the existence of a real world object
• Operations
  • Create
  • Read
  • Update
  • Delete

Deployment

Collection of resources

• wired together with Nix expressions
• reflecting some area of the real world

Operations

• CRUD

• "nix run"

  • backup
  • key rotation

Resource Provider

• Program built with Nix
• Called by NixOps
• JSON over stdio

Expressions

Simplified

{ # flake.nix
  outputs = inputs: {
    nixops4Deployments.default = { resources, ... }: {
      resources = {
        <resource name> = {
          ...
        };
      };
    };
  };
}

Expressions

{ resources, ... }: {
  resources = {
    "nixos" = {
      imports = [ inputs.nixos.modules.nixops4Resource.nixos ];
      inputs = {
        ssh.privateKey = resources.sshkeypair.privateKey;
        ssh.host = resources.host;
        module = ./configuration.nix;
      };
    };
  };
}

Expressions

{ resources, ... }: {
  resources = {
    "nixos" = ...;
    "sshkeypair" = {
      type = "ssh.keypair";
      inputs = {
        state = resources.state;
      };
    };
  };
}

Expressions

{ resources, ... }: {
  resources = {
    "nixos" = ...;
    "sshkeypair" = ...;
    "state" = {
      type = "s3.object";
      inputs = {
        endpoint = "https://garage.example.com";
        bucket = "nixops4-my-project";
      };
    };
  };
}

Expressions

{ config, resources, ... }: {
  options.customers = mkOption {
    type = attrsOf (submodule ./customer.nix);
  };
  config.resources = {
    "state" = ...;
    "sshkeypair" = ...;
    "nixos" = ... (foo config.customers) ...;
  };
}

Expressions

{ resources, ... }: {
  imports = [
    ./data-model.nix
    ./applications/pixelfed.nix
    ./applications/mastodon.nix
    ./applications/peertube.nix
  ];
}

Expressions

• resources monoid in the category of endofunctors 😉
• Structural composition like attrsOf or submodule
  • imports is mix-ins

top@{ resources, ... }: {
  resources = {
    "state" = ...;
    "my-host" = mkSequence ({ resources, ... }: {
      "sshkeypair" = ... top.resources.state.handle ...;
      "nixos" = ... resources.sshkeypair.privateKey ...;
    });
  };
}

Module author benefits

• All-Nix development experience
• No glue code
• All declarative

Application benefits

"NixPanel"

• Structured logging

• Separate evaluator for stability

Operator benefits

CLI for the backend

Integrate arbitrary scripts, no glue code

Operator benefits

Progress

Built, but subject to fixes and improvements

• nixops4/nixops4-eval process architecture
• Nix C API, Rust bindings
• Documentation tooling
• Testing

Progress

TBD

• mkSequence nesting / data dependencies
• Read, Update, Delete
• State management
• More resources, OpenTofu

Questions

Not discussed

• Resource naming within the state

  • read multiple => migrations

• resourceProviderSystem

Process Architecture

• nixops4
  • nixops4-eval -> libnixexpr etc (internal)
  • resource providers
    • nixops4-resources-local
    • nixops4-resources-opentofu (planned)
    • ...