Phoenix sub app live socket not routing

Phoenix Forum Questions / Help
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#1

My umbrella app routes calls through a “master proxy” which really is a big plug that has a bunch of redirections. Sample:

defmodule MasterProxy.Plug do
  alias MasterProxy.Plug.Request

  def init(options) do
    options
  end

  def call(conn, _opts) do
    cond do
        conn.request_path =~ ~r{/my_app} ->
          MyApp.Endpoint.call(conn, [])
.....
    end
  end
end

One of these redirects is towards a phoenix sub-app and it works fine except for the the live socket (used for phoenix live views).
It complains that the route for /live/websocket was not found even though my endpoint.ex contains:
socket "/live", Phoenix.LiveView.Socket as per the doc.
Now the weird part is that if I hit the sub-app directly on it’s port (say 4008 locally) then the socket seems to connect fine.
My guess is that something goes awry when it passes through the proxy redirect, but I can’t seem to figure out what?
Any clues?

#2

For anybody finding this post and wondering the same thing, it seems like sockets are directly wired into cowboy and are not handled by Plug. As a result, a master proxy approach cannot redirect a socket connection and the route will fail to be resolved.
It’s a limitation of this approach and afaik there is nothing you can do about it outside of routing to your sub-app directly and by-passing the master proxy.

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