Claper

Claper is a self‑hosted, real‑time interaction platform that turns static presentations into dynamic, audience‑engaged events. Built on the Phoenix framework and Elixir runtime, it delivers low‑latency WebSocket communication for polls, Q&A, quizzes, and form submissions while maintaining a clean separation between presentation logic and user interaction data. The core of the application is an event‑centric model where each session hosts a set of interactive widgets that can be added, reordered, or removed on the fly by the presenter.

Technical Stack

• Language & Runtime: Elixir (Erlang VM) provides fault tolerance and concurrency, essential for handling thousands of simultaneous WebSocket connections during a live event.
• Web Framework: Phoenix brings routing, channels, and the powerful Phoenix.LiveView stack for server‑rendered reactive UIs.
• Frontend: Tailwind CSS supplies a utility‑first styling layer, while Alpine.js or vanilla JavaScript powers lightweight interactivity on the client side.
• Database: PostgreSQL is used for persistent storage of events, users, polls, and responses. Ecto serves as the query layer, with migrations managed directly in Elixir.
• Real‑time: Phoenix Channels over WebSockets push updates to all connected clients, ensuring instant visibility of poll results and Q&A queues.
• Testing: ExUnit for unit tests, with integration tests exercising channel behavior and database consistency.

Core Capabilities

• Interactive Widgets: Exposes a plugin‑style API where developers can register new widget types (e.g., custom polls, quizzes, or forms) via Elixir modules that implement a defined behaviour.
• REST & GraphQL APIs: Provides authenticated endpoints for event creation, widget configuration, and result retrieval. Webhooks can be configured to push analytics or trigger downstream services (e.g., Slack notifications).
• Real‑time Dashboard: Phoenix.LiveView dashboards display live analytics, allowing developers to embed custom metrics or visualizations.
• Export & Analytics: CSV/JSON export endpoints aggregate session data, enabling post‑event analysis or integration with BI tools.

Deployment & Infrastructure

Claper is designed for containerized deployment. A single docker-compose.yml (or Helm chart) can spin up the application, PostgreSQL, and optional reverse proxy (NGINX/Traefik). The Elixir OTP release is self‑contained, requiring only a compatible runtime and the database. Horizontal scaling is achieved by running multiple Phoenix instances behind a load balancer; Elixir’s process supervision ensures graceful failover. For high‑volume events, a dedicated Redis cluster can be added to offload channel message brokering.

Integration & Extensibility

• Plugin System: Developers can extend Claper by implementing the Claper.Widget behaviour, registering the module in the application config. This allows custom widgets to be added without modifying core code.
• Webhooks & Callbacks: Each interaction emits events that can be consumed by external services. The webhook system supports JSON payloads and configurable retry logic.
• OAuth & SSO: Built‑in support for external authentication providers (Google, GitHub) simplifies integration into existing corporate identity stacks.
• Custom Themes: Tailwind’s configuration can be overridden, and CSS variables exposed for brand‑specific styling.

Developer Experience

• Documentation: The official docs (https://docs.claper.co/) provide comprehensive guides on architecture, API usage, and plugin development.
• Configuration: Environment‑based config files (config/*.exs) keep secrets and deployment settings separate from code.
• Community & Support: Active GitHub repository with a growing contributor base, Discord channel for real‑time help, and a dedicated subreddit.
• Licensing: GPLv3 encourages collaboration while ensuring that improvements remain open source.

Use Cases

1. Corporate Town Halls – Real‑time polling and Q&A to gauge employee sentiment during large meetings.
2. Educational Lectures – Interactive quizzes and forms embedded in lecture slides to boost engagement.
3. Webinars & Conferences – Audience interaction tools that can be hosted on the same domain as the event, eliminating third‑party integrations.
4. Remote Workshops – PDF/PPT upload with overlay widgets lets facilitators keep existing materials while adding interactivity.

Advantages

• Performance: Elixir’s lightweight processes handle thousands of concurrent WebSocket connections with minimal CPU overhead.
• Flexibility: The plugin architecture and comprehensive API allow developers to tailor the platform to niche workflows.
• Self‑Hosting: Full control over data privacy and compliance, essential for regulated industries.
• Cost‑Effectiveness: Open source under GPLv3, no per‑user licensing fees.
• Scalability: Designed to run on a single server for small events and scale horizontally via Docker or Kubernetes for enterprise deployments.