ActionCable does not close its hijacked I/O socket

[tinco]

Steps to reproduce

1. Start a web server using Phusion Passenger that opens a websocket connection
2. Refresh the page a few times

Expected behavior

There should never be more than 1 concurrent session when you run passenger-status. And when you close the website there should be 0.

Actual behavior

Sessions are leaked. The amount of open sessions will steadily increase.

System configuration

Rails version: Rails 5.0.0rc2 (and probably 5.0.0 too, so sorry I didn't know you guys were gonna release tonight)

Ruby version: 2.3

Hey guys sorry I was doing some performance testing using Phusion Passenger today, and I found this bug. I assume it's in Puma as well though I don't know how to make Puma give that info. I'll follow up with a PR.

Some extra info:

According to the Rack spec it is the applications responsibility to close the hijacked I/O socket after its done. This should likely be done in ActionCable::Connection::Stream#clean_hijacked_io.

[maclover7]

Closing in favor of #25615.