Streaming Rack with Falcon
Rack 3 introduced support for input and output streaming. This is a powerful feature that improves both performance and provides opportunities for enhanced interactivity in web applications. We will explore how to use streaming input and output in Rack, including server-sent events, streaming templates, streaming uploads, and bi-directional streaming. We will also discuss how to use these features in Ruby on Rails.
All the source code discussed in this article is available on GitHub. I recommend you check it out so you can follow along with the examples and try it out for yourself.
Streaming output is a feature that allows you to send data to the client as it is generated. This is useful for sending large amounts of data, such as video or audio streams, or for sending data that is generated over time, such as a log file or a real-time feed. Streaming output is supported in Rack by returning a callable object as the response body. This callable object will get invoked with a stream argument, which you can read and write to from within the block.
Streaming output can be a bit tricky to use in web browsers, as they may buffer the response. One way to work around this is to use Server-Sent Events (SSE), which are specifically handled by web browsers and are guaranteed to be unbuffered.
