Ably Pub/Sub vs Faye

Ably Pub/Sub has no write-up on Specifiction yet; its figures are above.

Faye is a publish-subscribe messaging system that uses the Bayeux protocol. It provides message servers for Node.js and Ruby, plus clients for servers and major web browsers. Browser clients rely on a Faye server to relay messages; they can retry after a lost connection and redeliver dropped messages. Transport adapters cover WebSocket, HTTP long-polling, Cross Origin Resource Sharing, and JSON-P callback-polling. Server and client extensions can intercept or modify messages, including to add subscription authentication. The monitoring API reports handshakes, subscriptions, unsubscriptions, publishes, and disconnections. Faye runs on Linux, macOS, and Windows, and can be self-hosted. Its default in-process engine cannot span multiple front-end web servers, but Redis and Couchbase engines are documented for distributed deployments. Faye is free and open source under the Apache 2.0 license; the listed plan is free. Install the Node.js server through npm or the Ruby server through RubyGems.