WebSockets in Ruby

The post says the service had to keep instant coordinate conversion feedback while avoiding a growing data download and heavy client-side loading. Because Ruby WebSocket options were limited, the author tested several approaches and settled on webmachine-ruby.

Reading notes

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• The original geocoding service was built in Ruby as a library plus a simple Sinatra webservice.
• The client later required a conversion on every mouse move, which led to a JavaScript version.
• Support for multiple Roads per User made larger downloads and client-side loading impractical.
• The author looked for a Ruby WebSocket solution and briefly considered using node.js instead.
• sinatra-websocket did not upgrade the connection to a WebSocket.
• faye-websocket was skipped.
• Rails-based options used too much memory on a small Heroku dyno and could crash during startup.
• webmachine-ruby was the remaining option.
• The author migrated the HTTP service to webmachine resources before adding WebSockets.
• webmachine-ruby uses a callable websocket handler through Reel.
• A handler can read from the socket and act on the message.
• The docs do not explain that the handler should loop on reads to avoid hanging.
• Celluloid::IO provides non-blocking socket reads.
• The author assigned each client to a Celluloid Actor to isolate CPU-intensive operations.
• The solution does not yet handle non-WebSocket clients.
• The author notes missing socket events and says the actor is allowed to crash in the current use case.
• The author mentions faye and websocket-rails as options when a pub/sub system is needed.