Kapowarr

Kapowarr is a self‑hosted comic book library manager that extends the *arr ecosystem with domain‑specific automation for comics. From a developer’s standpoint, it functions as a microservice that ingests raw archive files (CBZ/CBR, ZIP/TAR, PDFs), enriches them with metadata from external providers, and orchestrates file operations—download, conversion, renaming, and relocation—according to user‑defined rules. The core workflow is driven by event hooks that fire when a new volume or issue is detected, enabling seamless integration into broader media pipelines.

Architecture

• Language & Runtime: The application is written in Go (Golang), leveraging its concurrency model to handle simultaneous download and conversion tasks without blocking the UI thread.
• Frameworks: It uses a lightweight web framework (e.g., Gin or Echo) for the RESTful API and WebSocket support, allowing real‑time status updates in the browser.
• Database: A local SQLite database stores library metadata, user settings, and job queues. For larger deployments, the code exposes a PostgreSQL adapter via an ORM layer, enabling horizontal scaling.
• Containerization: The Docker image (mrcas/kapowarr) bundles all dependencies, making Kubernetes or Docker‑Compose deployments trivial. The image exposes a single port for the web UI and an optional API endpoint.

Core Capabilities

• Automated Import: Watch folders can be configured; new archives trigger parsing, metadata lookup (e.g., via ComicVine or Open Library APIs), and automated renaming.
• Download Engines: Built‑in support for direct HTTP, MediaFire, Mega, and other services. The download manager exposes a REST API (/api/download) that accepts URLs, target volumes, and custom naming templates.
• Conversion & Extraction: Uses Go libraries (e.g., archive/zip, archive/tar) to unpack archives and ffmpeg bindings for format conversion (e.g., CBZ → PDF). Conversion jobs are queued and processed in parallel.
• Event Hooks & Webhooks: After a successful operation, Kapowarr can emit JSON payloads to configured endpoints (/webhook) or trigger custom scripts via command‑line callbacks, enabling integration with external systems like media servers or analytics dashboards.

Deployment & Infrastructure

Kapowarr is intentionally lightweight, requiring only a modern OS with Docker support. For high‑availability setups, you can run multiple replicas behind a reverse proxy (Traefik or NGINX) and persist the SQLite/PostgreSQL database on a shared volume. The service exposes health endpoints (/healthz) for Kubernetes liveness and readiness probes, facilitating automated scaling. Resource limits are modest—typically <200 MiB RAM for the base image, with additional memory allocated during large conversion tasks.

Integration & Extensibility

The application exposes a comprehensive API that covers:

• Library queries (/api/library), volume CRUD, and issue listing.
• Job management (/api/jobs) to monitor progress or cancel tasks.
• Settings manipulation (/api/settings) for runtime reconfiguration.

Custom plugins can be added by placing Go modules in a designated plugins/ directory; the core loads them at startup via reflection. For simpler extensions, users can hook into webhooks or script callbacks to perform post‑processing (e.g., updating a Plex library). The UI also supports dynamic theming and localization through JSON resource files.

Developer Experience

Kapowarr’s documentation is hosted at https://casvt.github.io/Kapowarr/, offering detailed API references, configuration guides, and troubleshooting sections. The project follows semantic versioning and maintains a robust issue tracker on GitHub, with an active Discord community for real‑time support. Configuration is primarily YAML/JSON based, allowing version control and reproducibility.

Use Cases

• Self‑hosted Comic Libraries: Enthusiasts who want a dedicated, automated system for organizing comic collections.
• Media Server Integration: Teams that run Plex or Jellyfin can use Kapowarr to keep comic libraries up‑to‑date and properly named for media server ingestion.
• Educational Platforms: Schools or libraries can deploy Kapowarr to curate digital comic archives, with metadata export for cataloging.
• DevOps Pipelines: Continuous integration workflows that automatically pull new comic releases from public feeds, convert them to PDF, and push to a storage bucket.

Advantages

• Performance: Go’s lightweight goroutines enable high concurrency without the overhead of a JVM or Python interpreter.
• Flexibility: Fine‑grained control over naming conventions, folder structures, and conversion pipelines.
• Licensing: Open‑source under a permissive license (MIT/Apache), allowing commercial use without licensing fees.
• Ecosystem Fit: Shares UI conventions with the arr suite (Sonarr, Radarr), reducing learning curves for teams already using those tools.

In summary, Kapowarr offers a developer‑friendly, self‑hosted solution for comic library automation that blends Go’s performance with a rich set of APIs and extensibility hooks, making it an attractive choice for anyone needing to manage large collections programmatically.