Centrifugo

Centrifugo's server API is available via REST (POST /api with JSON body) and gRPC. Commands: publish (send to channel), broadcast (send to multiple channels), subscribe, unsubscribe, presence, presence_stats, history, history_remove, channels, info, disconnect. All commands are POST to /api with a JSON body containing method and params fields. Authentication to the server API uses an api_key header. The gRPC API mirrors the REST surface. SDK support: JavaScript, Go, Python, Ruby, PHP (Centrifuge client libs for connection; server API uses direct HTTP).

REST API returns standard HTTP status codes plus a Centrifugo-specific JSON envelope: { result: {...} } on success or { error: { code, message } } on failure. Error codes are numeric and documented. Publish to non-existent channels succeeds (message is dropped if no subscribers, or stored in history if configured). Connection errors are non-destructive for the API caller. History and presence queries return empty results for inactive channels. Rate limiting is configurable server-side but not enforced at the API level by default.

Centrifugo is a self-hosted real-time messaging server (Go) with WebSocket, SSE, and HTTP streaming support. It provides a server-side REST and gRPC API that agents can use to publish messages to channels, broadcast to user groups, query presence (who is subscribed), retrieve channel history, and manage connections. Agent relevance is good for backends that need to push real-time events to connected clients without managing WebSocket infrastructure. Centrifugo handles transport complexity; agents interact with the simple publish API. Centrifugo Cloud is a managed offering. Open-source (Apache 2.0). Confidence is docs-derived.

Server API authentication uses an HMAC or static api_key header. The api_key is configured server-side and must be kept secret — it grants full publish/admin access to all channels. Client connections use JWT tokens for user authentication and channel authorization. Channel permissions are defined via subscription tokens or server-side channel subscription callbacks. The api_key model is appropriate for agent-to-server communication; JWT-based client auth handles end-user permissions.

Documentation at centrifugal.dev/docs is comprehensive: server setup, client SDKs, server API reference, channel namespaces, JWT auth, and deployment guides. The server API reference documents all commands with request/response examples. Go-first documentation; other language examples are available. Community support via Telegram group and GitHub. Documentation quality is high for the core publish/subscribe use case; advanced features (Redis scaling, proxy callbacks) are well-documented for an open-source project.