Ruby Net::SSH Freeze when using "rails console" command over SSH

Question

I'm building a web based Terminal that runs against other server by SSH. I'm using Xterm.js for the UI and Net::SSH for the backend. The communication between the website and the backend is inside an ActionCable channel (WebSocket).

Everything is working perfectly, including interactive tools like nano or vim, however, for some reason when running the command "bundle exec rails c" which is meant to open a Ruby on Rails console, it hangs. The terminal becomes unresponsive, I can see I am trying to type in the terminal because ssh_channel.send_data payload.dig("data", "cmd") gets called, but no data is received anymore in channel.on_data

Here are the relevant lines of code:

 # Entry point
 def start(payload)
 connect!
 open_channel!
 open_connection_thread!
 broadcast_reply(payload["id"], "login", { result: :successful })
 end
 # Every single key typed in Xterm.js is passed here.
 def cmd(payload)
 ssh_channel.send_data payload.dig("data", "cmd")
 end
 private
 attr_accessor :ssh_client, :ssh_channel, :thread
 def connect!
 self.ssh_client ||= Net::SSH.start(
 "host_ip",
 "username",
 keys_only: true,
 use_agent: false,
 key_data: [ssh_private_key]
 )
 end
 def open_channel! # rubocop:disable Metrics/MethodLength
 self.ssh_channel ||= ssh_client.open_channel do |channel|
 channel.request_pty(term: "xterm-256color") do |ch, success|
 raise "Error requesting pty" unless success
 ch.send_channel_request("shell") do |_, result|
 raise "Error opening shell" unless result
 end
 end
 channel.on_data do |_, data|
 broadcast_reply(nil, :cmd_output, data)
 end
 channel.on_extended_data do |_, _, data|
 broadcast_reply(nil, :cmd_output, data)
 end
 channel.on_close { }
 end
 end
 def open_connection_thread!
 self.thread ||= Thread.new do
 # This is blocking and could be done outside a thread because the callbacks are called anyway.
 # However, this appears safer.
 ssh_client.loop(0.1)
 end
 end

Here is how it looks like

Frozen when running Rails console

I don't really know what to look for. Any kind of clue would be really appreciated!

Note: I tried an existing online SSH client like this one https://ssheasy.com/ and it appears to be working as expected. What would be wrong with my implementation?

• Igor: Are you able to you check (in a parallel normal SSH shell) what happens to the process itself?
• James St-Pierre: @Igor I can see the process is still running. What should I check (and how?)