Radarr

Radarr is a self‑hosted movie collection manager designed to automate the entire lifecycle of media acquisition—from RSS feed monitoring to quality upgrades. At its core, Radarr acts as a mediator between indexers (USENET or BitTorrent), download clients (SABnzbd, NZBGet, qBittorrent, etc.), and media servers such as Plex or Kodi. Developers will appreciate its RESTful API, which exposes every operational aspect—movie metadata, download queue manipulation, profile configuration, and event hooks—allowing seamless integration into custom workflows or orchestration platforms.

Architecture & Technical Stack

Radarr is built on .NET Core (now .NET 6+) and follows a layered architecture:

• Presentation Layer: ASP.NET Core MVC/Web API serving both the web UI and JSON endpoints. The UI is a lightweight SPA using React with server‑side rendering for SEO and performance.
• Business Layer: Domain services encapsulate movie logic, profile matching, and quality decision making. These services interact with the EF Core data context.
• Data Layer: Persistent storage is handled by SQLite in the default Docker image, with optional support for PostgreSQL or MySQL via connection string overrides. EF Core migrations keep the schema in sync.
• Background Workers: Hosted services run periodic tasks (RSS sync, download monitoring, quality upgrade checks) using the IHostedService pattern. These workers are highly configurable via JSON settings.

The application is cross‑platform, running natively on Windows, Linux, macOS, and ARM architectures (e.g., Raspberry Pi), thanks to .NET’s universal runtime.

Core Capabilities & APIs

• Metadata Harvesting: Radarr queries TMDB/OMDb for trailers, ratings, and cast lists. The API exposes endpoints to retrieve or update this metadata programmatically.
• Quality Profiles: Developers can define JSON schemas for quality tiers (e.g., 1080p HDTV, 4K Blu‑Ray) and expose them via the /api/qualityprofile endpoint.
• Download Integration: REST calls to /api/downloadclient allow adding, pausing, or removing jobs. Radarr can also push release details to clients via their native APIs.
• Webhooks & Event System: Events such as movieAdded, downloadComplete, or qualityUpgrade can be subscribed to, enabling automation in CI/CD pipelines or custom notification services.
• Plugin Extensibility: Radarr supports a simple plugin interface where assemblies can hook into lifecycle events. This is ideal for adding custom validation or post‑processing logic.

Deployment & Infrastructure

Radarr ships as a Docker container (linuxserver/radarr), simplifying deployment on Kubernetes, Docker Swarm, or home‑lab orchestrators. The container exposes a single HTTP port (80/443) and mounts volumes for:

• /config – application settings, SQLite database, and logs.
• /downloads – shared folder for download clients to place completed files.
• /movies – target media library.

For scaling, Radarr is stateless aside from its database; thus multiple instances can run behind a load balancer, each targeting distinct media libraries or quality profiles. The use of SQLite keeps the footprint minimal, but for high‑traffic environments a production database (PostgreSQL/MySQL) is recommended.

Integration & Extensibility

• Media Server Hooks: Radarr can notify Plex or Kodi via HTTP callbacks, prompting library rescans after new movies are imported.
• Custom Indexers: Through the /api/indexer endpoint, developers can add or remove indexer sources (e.g., custom NZB sites) and set authentication tokens.
• Scheduled Tasks: The internal scheduler can be overridden via the API, allowing external cron jobs to trigger RSS syncs or quality checks.
• Plugin Ecosystem: Community plugins extend Radarr’s functionality—examples include automated subtitle fetching, custom release filtering, or integration with external database services.

Developer Experience

Radarr’s documentation is comprehensive: the API docs (https://radarr.video/docs/api/) provide endpoint summaries, request/response schemas, and example payloads. The open‑source codebase is hosted on GitHub with an active contributor community, issue tracker, and a dedicated Discord channel for real‑time support. Configuration is primarily JSON‑based, making it easy to version control or inject via environment variables in containerized deployments.

Use Cases

• Automated Home Media Library: Deploy Radarr alongside SABnzbd/NZBGet to maintain a curated movie collection with automatic quality upgrades.
• Enterprise Media Management: Integrate Radarr into a larger media ingestion pipeline, using its API to trigger downstream processing (transcoding, DRM) after download completion.
• Custom Monitoring Solutions: Leverage webhooks to trigger alerts or dashboards whenever new releases are added, facilitating real‑time analytics.

Advantages Over Alternatives

• Performance & Resource Efficiency: .NET Core’s lightweight runtime and SQLite default storage keep memory usage low, suitable for Raspberry Pi deployments.
• Extensibility: The plugin system and rich API surface allow developers to tailor Radarr to niche workflows without modifying core code.
• Licensing: Completely free and open‑source under the MIT license, with no vendor lock‑in.
• Community & Support: A vibrant developer community ensures rapid bug fixes, feature additions, and third‑party integrations.

Radarr’s blend of a solid .NET foundation, flexible architecture, and developer-friendly APIs makes it an attractive choice for anyone looking to automate media acquisition while