Cat

Errors when using SSL and reloading page too fast on slow-responding server

I’ve been trying to debug this for days, and I can’t figure out what I’m doing wrong. If SSL is off, I can reload the page as fast as I want and I don’t encounter any errors. But when I turn SSL on and try refreshing the page quickly, repeatedly, I get an error after the 5th or 10th reload.

Steps to reproduce

1. Start with a fresh `elixir` Docker container.

docker run -it --rm -w /opt -p 4000:4000 -p 4001:4001 elixir bash

2. Generate a simple Phoenix app

apt-get update && apt-get install inotify-tools -y
mix archive.install hex phx_new --force
mix phx.new hello --no-ecto --install
cd hello

3. Generate a self-signed cert needed for SSL

mix phx.gen.cert

4. Configure the endpoint

Change the IP to 0.0.0.0 to allow access from outside the container
```
sed -i 's/{127, 0, 0, 1}/{0, 0, 0, 0}/' config/dev.exs
```

Uncomment the self-cert https block

sed -ie '/# \{5\}https/,/# \{5\}],/ { s/^#//; }' config/dev.exs

Config Bandit to output client closures

sed -ie '/certfile/,/],/ { s/"$/",\n       http_options: [log_client_closures: :verbose]/; s/],/]/; }' config/dev.exs

Add a necessary comma after the watchers config option

sed -zie '/watchers/,/]\n/ { s/]\n/],\n/ }' config/dev.exs

Endpoint config in config/dev.exs should look like this:

config :hello, HelloWeb.Endpoint,
  http: [ip: {0, 0, 0, 0}, port: 4000],
  ...
  watchers: [
    ...
  ],
  https: [
    port: 4001,
    cipher_suite: :strong,
    keyfile: "priv/cert/selfsigned_key.pem",
    certfile: "priv/cert/selfsigned.pem",
    http_options: [log_client_closures: :verbose]
  ]

5. Configure the controller

Add a 1-second sleep to the controller home action to simulate a slow server response:

sed -ie '/render/ { s/^/    Process.sleep(1000)\n/ }' lib/hello_web/controllers/page_controller.ex

The home action in lib/hello_web/controllers/page_controller.ex should now look like this:

def home(conn, _params) do
  ...
  Process.sleep(1000)
  render(conn, :home, layout: false)
end

6. Start the server

iex -S mix phx.server

7. Test with the `HTTPS` scheme

Visit https://localhost:4001 with your browser. It will complain about the certificates. Bypass and continue.

Now, reload the page repeatedly as fast as you can. After about the 5th or 10th reload, you should start encountering problems. With Firefox, I don’t see any errors in the console, but Firefox does eventually render a “Network protocol error” page. When I try it with Chromium and Gnome Web browsers, I see the following error in the console:

Error output

[info] Sent 500 in 1010ms
[error] ** (Bandit.TransportError) Client reset stream normally
    (bandit 1.6.1) lib/bandit/http2/stream.ex:386: Bandit.HTTPTransport.Bandit.HTTP2.Stream.do_recv_rst_stream!/2
    (bandit 1.6.1) lib/bandit/adapter.ex:230: Bandit.Adapter.send_data/3
    (bandit 1.6.1) lib/bandit/adapter.ex:113: Bandit.Adapter.send_resp/4
    (plug 1.16.1) lib/plug/conn.ex:444: Plug.Conn.send_resp/1
    (hello 0.1.0) lib/hello_web/controllers/page_controller.ex:1: HelloWeb.PageController.action/2
    (hello 0.1.0) lib/hello_web/controllers/page_controller.ex:1: HelloWeb.PageController.phoenix_controller_pipeline/2
    (phoenix 1.7.18) lib/phoenix/router.ex:484: Phoenix.Router.__call__/5
    (hello 0.1.0) lib/hello_web/endpoint.ex:1: HelloWeb.Endpoint.plug_builder_call/2
    (hello 0.1.0) deps/plug/lib/plug/debugger.ex:136: HelloWeb.Endpoint."call (overridable 3)"/2
    (hello 0.1.0) lib/hello_web/endpoint.ex:1: HelloWeb.Endpoint.call/2
    (phoenix 1.7.18) lib/phoenix/endpoint/sync_code_reload_plug.ex:22: Phoenix.Endpoint.SyncCodeReloadPlug.do_call/4
    (bandit 1.6.1) lib/bandit/pipeline.ex:127: Bandit.Pipeline.call_plug!/2
    (bandit 1.6.1) lib/bandit/pipeline.ex:36: Bandit.Pipeline.run/4
    (bandit 1.6.1) lib/bandit/http2/stream_process.ex:27: Bandit.HTTP2.StreamProcess.handle_continue/2
    (stdlib 6.1.2) gen_server.erl:2335: :gen_server.try_handle_continue/3
    (stdlib 6.1.2) gen_server.erl:2244: :gen_server.loop/7
    (stdlib 6.1.2) proc_lib.erl:329: :proc_lib.init_p_do_apply/3