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Actors
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Maintainers
The group developing and maintaining this project. We are creating the deployment workflows and service configurations, and curate changes proposed by contributors.
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Contributors
People with the technical background to engage with our work, and may contribute back, build on top of, remix, or feel inspired by our work to create something better.
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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.
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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.
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User
They are individuals using applications run by the operators, and e.g. post content.
Glossary
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A collection of social networking applications that can communicate with each other using a common protocol.
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Application
User-facing software (e.g. from Fediverse) configured by operators and used by users.
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Configuration
A collection of settings for a piece of software.
Example: Configurations are deployed to VMs.
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Provision
Make a resource, such as a virtual machine, available for use.
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Deploy
Put software onto computers. The software includes technical configuration that links software components.
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Migrate
Move service configurations and deployment (including user data) from one hosting provider to another.
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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.
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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.
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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.
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Runtime environment
The thing a deployment runs on, an interface against which the deployment is working. See runtime backend.
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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
OctoDNS
OctoDNS is a DNS server that may be configured using the Nix-native NixOS-DNS.
Considered alternatives include:
- PowerDNS: offers a front-end option, but less geared toward the use-case of configuring by Nix
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
Attic
Attic is a multi-tenant Nix cache featuring recency-based garbage collection written in Rust.
Considered alternatives include:
- cache-server: distributed cache written in Python that seems more of a research project than an actively maintained repository.
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:
- domain registration: involves a (manual) update of DNS records at the registrar
- deployed applications: using the reproducible configuration module
- application data:
- back-up/restore scripts using SelfHostBlocks
- application-specific migration scripts, to e.g. reconfigure of connections/URLs
Data model
Whereas the bulk of our configuration logic is covered in the configuration schema, our reference front-end application does in fact store data. The design for its data model to support the desired functionality is as follows, using the crow's foot notation to denote cardinality:
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:
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: