Running elixir from Erlang release

Hello, I am creating a project where I mix Erlang and Elixir applications.
I can do this when running Erlang by executing erl manually from my bash shell and adding the path to the elixir installation using the Erlangs code module, like this:

$> erl
Erlang/OTP 24 [erts-12.0] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [jit]
Eshell V12.0  (abort with ^G)
1> application:start(compiler).
ok
2> code:add_path("/usr/local/lib/elixir/lib/elixir/ebin").
true
3> application:start(elixir).
ok

However, when I do the exact same inside a release that I built with rebar3, it seems like the VM can not execute any code, even if it finds the elixir.app file.

$>bin/ao_devserver console
Erlang/OTP 24 [erts-12.0] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:30] [jit]
Eshell V12.0  (abort with ^G)
(ao_devserver@pop-os)1> application:start(compiler).
{error,{already_started,compiler}}
(ao_devserver@pop-os)2> code:add_path("/usr/local/lib/elixir/lib/elixir/ebin").
true
(ao_devserver@pop-os)3> application:start(elixir).
=CRASH REPORT==== 24-Apr-2022::06:19:38.775000 ===
  crasher:
    initial call: application_master:init/4
    pid: <0.998.0>
    registered_name: []
    exception exit: {bad_return,
                        {{elixir,start,[normal,[]]},
                         {'EXIT',
                             {undef,
                                 [{elixir,start,[normal,[]],[]},
                                  {application_master,start_it_old,4,
                                      [{file,"application_master.erl"},
                                       {line,293}]}]}}}}
      in function  application_master:init/4 (application_master.erl, line 142)
    ancestors: [<0.997.0>]
    message_queue_len: 1
    messages: [{'EXIT',<0.999.0>,normal}]
    links: [<0.997.0>,<0.791.0>]
    dictionary: []
    trap_exit: true
    status: running
    heap_size: 987
    stack_size: 29
    reductions: 156
  neighbours:

=INFO REPORT==== 24-Apr-2022::06:19:38.776020 ===
    application: elixir
    exited: {bad_return,
                {{elixir,start,[normal,[]]},
                 {'EXIT',
                     {undef,
                         [{elixir,start,[normal,[]],[]},
                          {application_master,start_it_old,4,
                              [{file,"application_master.erl"},
                               {line,293}]}]}}}}
    type: temporary

{error,
    {bad_return,
        {{elixir,start,[normal,[]]},
         {'EXIT',
             {undef,
                 [{elixir,start,[normal,[]],[]},
                  {application_master,start_it_old,4,
                      [{file,"application_master.erl"},{line,293}]}]}}}}}

I spent two evenings trying to figure this out, reading on stack-overflow, these forums etc but could not find anyone with same problem as me, maybe I am doing it wrong?

1 Like

More a workaround to your issue, but mix can compile erlang and elixir source code side by side (lib folder for elixir code, src for erlang code).

2 Likes

I made some progress, I discovered that starting my release with as “console_clean”, I can start the elixir application with no errors:

bin/ao_devserver console_clean
Exec: /usr/local/lib/erlang/erts-12.0/bin/erlexec -boot Erlang/OTP 24 [erts-12.0] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:30] [jit]

Eshell V12.0  (abort with ^G)
(ao_devserver@pop-os)1> application:start(compiler).
ok
(ao_devserver@pop-os)2> application:start(elixir).  
{error,{"no such file or directory","elixir.app"}}
(ao_devserver@pop-os)3> code:add_path("/usr/local/lib/elixir/lib/elixir/ebin").
true
(ao_devserver@pop-os)4> application:start(elixir).                             
ok
(ao_devserver@pop-os)5>

I have yet not discovered exactly why yet but it has to do with some of the difference in the start parameters from the starting with just “console”.

Your release is likely running in embedded mode, which means code is not loaded interactively.

1 Like

Your wise council belies your years Mr. Valim.

Indeed my problem was that the script which runs the release starting erlang in embedded mode:
erl -mode embedded

If someone in the future experience the same problem, I am glad to let you know that this can be controlled by setting the CODE_LOADING_MODE environment variable and then calling the release start script:

export CODE_LOADING_MODE=-interactive

./bin/ao_devserver console
(ao_devserver@pop-os)1> code:add_path("/usr/local/lib/elixir/lib/elixir/ebin/").
true
(ao_devserver@pop-os)2> application:start(elixir).
ok
(ao_devserver@pop-os)3>
1 Like