"/rel/<projectname>/bin/<projectname> stop" does not work

[farao]

Same problem like in exrm: bitwalker/exrm#385
It works neither on my laptop (current arch linux) nor on my server (Debian wheezy).

[bitwalker]

Can you provide a sample project I can reproduce this with? My own tests have not produced the same issue. I haven't yet tried with an Arch or Debian VM, but I want to make sure this is truly a platform-specific issue and not something more general.

[farao]

You can try this Dockerfile:
Dockerfile.zip

1. Download into new directory & unzip
2. sudo docker build ./
3. sudo docker run -t -i idofdockercontainerfromlastlineoftheoutputofcommand2
4. (inside docker container) cd signaltower
5. rel/signal_tower/bin/signal_tower start
6. rel/signal_tower/bin/signal_tower stop

=> command 6 does not terminate

[farao]

Ok, better try this Dockerfile, I added mix release.init:
Dockerfile.zip

Also I now updated the signaltower repository to use distillery instead of exrm, but the error concerns both as written.

[bitwalker]

So the issue here is actually with the app. The problem I found was that when the application master attempts to shut down the signal_tower app, it hangs, and I'm almost certain it's due to the fact that you weren't returning the pid of a supervisor, but of the cowboy HTTP listener. Here's the changes I applied to the signaltower repo to get things working:

diff --git a/lib/signal_tower.ex b/lib/signal_tower.ex
index 80c71ee..daa8e57 100644
--- a/lib/signal_tower.ex
+++ b/lib/signal_tower.ex
@@ -1,28 +1,19 @@
 defmodule SignalTower do
-  @behaviour :application
+  use Application

   def start(_type, _args) do
     import Supervisor.Spec, warn: false

-    start_supervisor()
-    start_cowboy()
-  end
-
-  def stop(_state) do
-    :ok
-  end
-
-  defp start_cowboy() do
     {port, _} = Integer.parse(System.get_env("PALAVA_RTC_ADDRESS") || "4233")

     dispatch = :cowboy_router.compile([
       {:_, [{"/[...]", SignalTower.WebsocketHandler, []}]} # TODO check [] if removable
     ])

-    {:ok, _} = :cowboy.start_http(:http, 100, [{:port, port}], [{:env, [{:dispatch, dispatch}]}])
-  end
-
-  defp start_supervisor() do
-    SignalTower.Supervisor.start_link(%{})
+    children = [
+      supervisor(SignalTower.Supervisor, []),
+      worker(:cowboy, [:http, 100, [port: port], [env: [dispatch: dispatch]]], function: :start_http)
+    ]
+    Supervisor.start_link(children, strategy: :one_for_one)
   end
 end
diff --git a/lib/supervisor.ex b/lib/supervisor.ex
index f55f07b..47f8a94 100644
--- a/lib/supervisor.ex
+++ b/lib/supervisor.ex
@@ -1,8 +1,8 @@
 defmodule SignalTower.Supervisor do
   use Supervisor

-  def start_link(opts) do
-    Supervisor.start_link(__MODULE__, opts)
+  def start_link() do
...skipping...
@@ -1,28 +1,19 @@
 defmodule SignalTower do
-  @behaviour :application
+  use Application

   def start(_type, _args) do
     import Supervisor.Spec, warn: false

-    start_supervisor()
-    start_cowboy()
-  end
-
-  def stop(_state) do
-    :ok
-  end
-
-  defp start_cowboy() do
     {port, _} = Integer.parse(System.get_env("PALAVA_RTC_ADDRESS") || "4233")

     dispatch = :cowboy_router.compile([
       {:_, [{"/[...]", SignalTower.WebsocketHandler, []}]} # TODO check [] if removable
     ])

-    {:ok, _} = :cowboy.start_http(:http, 100, [{:port, port}], [{:env, [{:dispatch, dispatch}]}])
-  end
-
-  defp start_supervisor() do
-    SignalTower.Supervisor.start_link(%{})
+    children = [
+      supervisor(SignalTower.Supervisor, []),
+      worker(:cowboy, [:http, 100, [port: port], [env: [dispatch: dispatch]]], function: :start_http)
+    ]
+    Supervisor.start_link(children, strategy: :one_for_one)
   end
 end
diff --git a/lib/supervisor.ex b/lib/supervisor.ex
index f55f07b..47f8a94 100644
--- a/lib/supervisor.ex
+++ b/lib/supervisor.ex
@@ -1,8 +1,8 @@
 defmodule SignalTower.Supervisor do
   use Supervisor

-  def start_link(opts) do
-    Supervisor.start_link(__MODULE__, opts)
+  def start_link() do
+    Supervisor.start_link(__MODULE__, [])
   end

   def init(_) do

And I used this Dockerfile to test:

FROM debian:wheezy

ENV MIX_ENV=prod

RUN apt-get update && \
    apt-get -y install wget

WORKDIR /opt/code

RUN \
  wget --no-check https://packages.erlang-solutions.com/erlang-solutions_1.0_all.deb && dpkg -i erlang-solutions_1.0_all.deb &&\
  apt-get update && \
  apt-get -y install elixir && \
  apt-get -y install git && \
  mix local.hex --force && \
  mix local.rebar --force

ADD mix.exs mix.lock ./
RUN mix do deps.get, deps.compile

ADD . .
RUN mix release --verbose --env=prod && \
    mkdir -p /opt/app && \
    cd /opt/app && \
    ls -la /opt/code/rel/signal_tower/releases/1.0.0 && \
    cp /opt/code/rel/signal_tower/releases/1.0.0/signal_tower.tar.gz ./ && \
    tar -xzf signal_tower.tar.gz && \
    mkdir -p ./log && \
    chown -R 777 /opt/app && \
    rm -rf /opt/code

WORKDIR /opt/app

I'm going to close this since it's not an issue with distillery (or exrm)

[farao]

Oh, hmmmm. Strange though that there was no part (elixir compiler, mix or distillery) that warned about this - shouldn't there be a message if the programmer forgets to return the pid of the root supervisor?

Sorry for stealing your time though and thanks a lot for pointing out the problem and solving it at the same time!

[bitwalker]

Even dialyzer wouldn't have caught this, because the value you were returning was actually {:ok, pid}, which is what the expected return signature is supposed to be. It's just that the pid was for a process not in your application. Unfortunately I'm not sure that the compiler could ever catch this kind of thing, it's a tricky one for sure.