Friendship Ended with Rack::BodyProxy | Rails at Scale

The application responds to #call with a single argument, the environment, and returns an array of status, headers, body. All of the concepts seem straightforward, right? The status is an Integer, the environment and response headers are Hashes, and the body is an Array of Strings. While this is a valid Rack application, that’s not really the end of the story. For the whole picture, we have to read the Rack SPEC. For this post, let’s focus on the specification of the body. The requirements have evolved over time, but something that hasn’t changed since the earliest versions1 of Rack is that enumerable bodies should respond to #each, yielding strings. That means an application that prefers not to buffer its entire response into memory could implement the body like this:.