kiara/fedi-goals
1
0
Fork 1
Code Issues Pull requests 1 Projects Releases Packages Wiki Activity Actions
fedi-goals/architecture.md

19 KiB
Raw Blame History

Actors

  • Developers

    The group maintaining this repository. We are creating the deployment workflows and service configurations, and curate changes proposed by contributors.

  • Contributors

    People proposing changes to this repository.

  • Hosting provider

    They provide and maintain the physical infrastructure, and run the software in this repository, through which operators interact with their deployments. Hosting providers are technical administrators for these deployments, ensuring availability and appropriate performance.

    We target small- to medium-scale hosting providers with 20+ physical machines.

  • Operator

    They select the applications they want to run. They don't need to own hardware or deal with operations. Operators administer their applications in a non-technical fashion, e.g. as moderators. They pay the hosting provider for registering a domain name, maintaining physical resources, and monitoring deployments.

  • User

    They are individuals using applications run by the operators, and e.g. post content.

Glossary

  • Fediverse

    A collection of social networking applications that can communicate with each other using a common protocol.

  • Application

    User-facing software (e.g. from Fediverse) configured by operators and used by users.

  • Configuration

    A collection of settings for a piece of software.

    Example: Configurations are deployed to VMs.

  • Provision

    Make a resource, such as a virtual machine, available for use.

  • Deploy

    Put software onto computers. The software includes technical configuration that links software components.

  • Migrate

    Move service configurations and deployment (including user data) from one hosting provider to another.

  • Resource

    A resource for NixOps4 is any external entity that can be declared with NixOps4 expressions and manipulated with NixOps4, such as a virtual machine, an active NixOS configuration, a DNS entry, or customer database.

  • Resource provider

    A resource provider for NixOps4 is an executable that communicates between a resource and NixOps4 using a standardised protocol, allowing CRUD operations on the resources to be performed by NixOps4. Refer to the NixOps4 manual for details.

    Example: We need a resource provider for obtaining deployment secrets from a database.

  • Runtime backend

    A type of digital environment one can run operating systems such as NixOS on, e.g. bare-metal, a hypervisor, or a container runtime.

  • Runtime environment

    The thing a deployment runs on, an interface against which the deployment is working. See runtime backend.

  • Runtime config

    Configuration logic specific to a runtime backend, e.g. how to deploy, how to access object storage.

Technologies used

NixOS

NixOS is a Linux distribution with a vibrant, reproducible and security-conscious ecosystem. As such, we see NixOS as the only viable way to reliably create a reproducible outcome for all the work we create.

Considered alternatives include:

  • containers: do not by themselves offer the needed reproducibility

npins

Npins is a dependency pinning tool for Nix which leaves recursive dependencies explicit, keeping the consumer in control.

Considered alternatives include:

  • Flakes: defaults to implicitly following recursive dependencies, leaving control with the publisher.

SelfHostBlocks

SelfHostBlocks offers Nix module contracts to decouple application configuration from implementation details, empowering user choice by providing sane defaults yet a unified interface. Offered contracts include back-ups, reverse proxies, single sign-on and LDAP. In addition, we have been in contact with its creator.

Considered alternatives include:

  • nixpkgs-provided NixOS service modules: support far more applications, but tightly coupled with service providers, whereas we expect them to sooner or later follow suit.
  • NixOS service modules curated from scratch: would support any setup imaginable, but does not seem to align as well with our research-oriented goals.

OpenTofu

OpenTofu is the leading open-source framework for infrastructure-as-code. This has led it to offer a vibrant ecosystem of 'provider' plugins integrating various programs and services. As such, it can facilitate automated deployment pipelines, including with — relevant to our project — hypervisors and DNS programs.

Considered alternatives include:

  • Terraform: not open-source

Proxmox

Proxmox is a hypervisor, allowing us to create VMs for our applications while adhering to our goal of preventing lock-in. In addition, it has been packaged for Nix as well, simplifying our requirements to users setting up our software.

Considered alternatives include:

  • OpenNebula: seemed less mature

Garage

Garage is a distributed object storage service. For compatibility with existing clients, it reuses the protocol of Amazon S3.

Considered alternatives include:

  • file storage: less centralized for backups

PostgreSQL

PostgreSQL is a relational database. It is used by most of our applications.

Considered alternatives include:

  • Sqlite: default option for development in many applications, but less optimized for performance, and less centralized for backups

Valkey

Valkey is a key-value store. It is an open-source fork of Redis.

Considered alternatives include:

  • Redis: not open-source

OpenSearch

OpenSearch offers full-text search, and is used for this in many applications. It is an open-source fork of ElasticSearch.

Considered alternatives include:

  • ElasticSearch: not open-source

PowerDNS

PowerDNS is a mature DNS server. It further offers an admin front-end.

Considered alternatives include:

  • hickory-dns: no front-end
  • core-dns: no front-end

Authelia

Authelia is a single sign-on provider that integrates with LDAP.

Considered alternatives include:

  • KaniDM: does not do proper LDAP
  • Authentik: larger package with focus on many things we do not need
  • Keycloak: larger package with focus on many things we do not need

lldap

Lldap is a light LDAP server, allowing to centralize user roles across applications.

Considered alternatives include:

  • 389 DS: older larger package
  • FreeIPA: wrapper around 389 DS

Architecture

At the core of Fediversity lies a NixOS configuration module for a set of selected applications. We will support using it with different run-time environments, such as a single NixOS machine or a ProxmoX hypervisor. Depending on the targeted run-time environment, deployment will further involve OpenTofu as an orchestrator. We further provide a reference front-end to configure applications. To ensure reproducibility, we also offer Nix packaging for our software.

To reach our goals, we aim to implement the following interactions between actors (depicted with rounded corners) and system components (see the glossary, depicted with rectangles).

Service portability

The process of migrating one's applications to a different host encompasses:

  1. domain registration: involves a (manual) update of DNS records at the registrar
  2. deployed applications: using the reproducible configuration module
  3. application data:
    • back-up/restore scripts using SelfHostBlocks
    • application-specific migration scripts, to e.g. reconfigure of connections/URLs

Relationships among the entities used to model migrations are as follows, using the crow's foot notation to denote cardinality:

Data model

Host architecture

Whereas the core abstraction in Fediversity is a NixOS configuration module, a more full-fledged example architecture of the web host use-case we aim to support as part of our exploitation would be as follows, where VMs in question run Fediversity to offer our selected applications:

Sample configuration schema

Whereas Nix(OS) option modules use Nix to specify types, in order to communicate the expected schema to other tools such as web applications, we use JSON Schema as an intermediate format, building upon earlier work converting between such schemas by Nix collective Clan. An example of such a schema might looks as follows:

{
  "$exportedModuleInfo": {
    "path": []
  },
  "$schema": "http://json-schema.org/draft-07/schema#",
  "additionalProperties": false,
  "properties": {
    "domain": {
      "$exportedModuleInfo": {
        "path": [
          "domain"
        ]
      },
      "default": "fediversity.net",
      "description": "Apex domain under which the services will be deployed.\n",
      "enum": [
        "fediversity.net"
      ]
    },
    "enable": {
      "$exportedModuleInfo": {
        "path": [
          "enable"
        ]
      },
      "default": false,
      "description": "Whether to enable Fediversity configuration.",
      "examples": [
        true
      ],
      "type": "boolean"
    },
    "initialUser": {
      "$exportedModuleInfo": {
        "path": [
          "initialUser"
        ]
      },
      "default": null,
      "description": "Some services require an initial user to access them.\nThis option sets the credentials for such an initial user.\n",
      "oneOf": [
        {
          "type": "null"
        },
        {
          "$exportedModuleInfo": {
            "path": [
              "initialUser"
            ]
          },
          "additionalProperties": false,
          "properties": {
            "displayName": {
              "$exportedModuleInfo": {
                "path": [
                  "initialUser",
                  "displayName"
                ]
              },
              "description": "Display name of the user",
              "type": "string"
            },
            "email": {
              "$exportedModuleInfo": {
                "path": [
                  "initialUser",
                  "email"
                ]
              },
              "description": "User's email address",
              "type": "string"
            },
            "password": {
              "$exportedModuleInfo": {
                "path": [
                  "initialUser",
                  "password"
                ]
              },
              "description": "Password for login",
              "type": "string"
            },
            "username": {
              "$exportedModuleInfo": {
                "path": [
                  "initialUser",
                  "username"
                ]
              },
              "description": "Username for login",
              "type": "string"
            }
          },
          "required": [
            "displayName",
            "email",
            "password",
            "username"
          ],
          "type": "object"
        }
      ]
    },
    "forgejo": {
      "$exportedModuleInfo": {
        "path": [
          "forgejo"
        ]
      },
      "default": null,
      "description": "Configuration for the Forgejo service\n",
      "oneOf": [
        {
          "type": "null"
        },
        {
          "$exportedModuleInfo": {
            "path": [
              "forgejo"
            ]
          },
          "additionalProperties": false,
          "properties": {
            "enable": {
              "$exportedModuleInfo": {
                "path": [
                  "forgejo",
                  "enable"
                ]
              },
              "default": false,
              "description": "Whether to enable Forgejo.",
              "examples": [
                true
              ],
              "type": "boolean"
            }
          },
          "type": "object"
        }
      ]
    }
  },
  "type": "object"
}

Break-down of project milestones

Whereas details of the implementation may need to be decided as the technical challenges involved become clear, we can already give a higher-level planning of relevant milestones and some of their salient features:

  1. Implement a way to run online services emphasising user autonomy and portability
  2. Disseminate our results by engaging the open-source community to further expand on work in this direction
  3. Exploit our work by facilitating the sample use-case of web hosting organisations using an initial set of services