great work replicating it..
can you post file sizes of said files - I presume the ones leaking are larger/above some threshold than the ones not leaking..
(eg cowboy keeps the file open awaiting further reads - for smaller files cowboy just reads it all in one go and doesn’t leak)
also what cowboy version are you on and does it leak on latest as well?
also for cowboy2 have you by any chance changed “idle_timeout”?
protocol_options: [idle_timeout: xx] - which defaults to 60 secs - New default timeout of 60s in Cowboy 2 · Issue #3190 · phoenixframework/phoenix · GitHub
