Running Migrations Automatically pre_start in Elixir-Distillery-Release on Windows - windows

Question

i need your help!
im trying to run migrations in a distillery release (Elixir-Application) before the application starts automatically (via Boot Hooks -https://hexdocs.pm/distillery/boot-hooks.html#content).
Development and Production platform must be Windows.
The Problem: I cant find any infos about Windows (.bat)-Scripts referencing the problem - I search for a script for the "pre_start.bat"-File - for calling the ERTS Node and finally my Elixir-Code in it.
my distillery-config : rel\config.exs
environment :prod do
...
set pre_start_hook: "rel/hooks/pre_start"
...
end
The required script should call my code of the "Elixir.MyApp.ReleaseTask.migrate"-Function
How can i achieve this??
The following Code is what ive got so far.. but it doesnt work ..
#echo off
echo Running migrations
echo.
echo.
echo.
cd %RELEASE_ROOT_DIR%
#set system_erl="<erl_directory>\erts-9.1\bin\erl.exe"
#set erl=%system_erl%
#set system_root_dir_cmd=%system_erl% -noshell -eval "io:format(\"~s\", [filename:nativename(code:root_dir())])." -s init stop
#set rootdir=%system_root%
#set system_erts_vsn_cmd=%system_erl% -noshell -eval "Ver=erlang:system_info(version),io:format(\"~s\", [Ver])" -s init stop
#set erts_vsn=%system_erts_vsn%
#set erts_dir=%rootdir%\erts-%erts_vsn%
#set rel_name="my_api"
#set rel_vsn="1.0"
#set consolidated_dir=%rootdir%\lib\%rel_name%-%rel_vsn%\consolidated
#%erl% -boot_var ERTS_LIB_DIR "%erts_dir%\..\lib" ^
-hidden -noshell -boot start_clean ^
-pa "%consolidated_dir%" ^
-s "Elixir.MyApp.ReleaseTasks" "seed" -s init stop
echo Migrations run successfully
Please correct me when im totally wrong with this.
Any help appreciated! BTW its a phoenix-Application.

Answer 1

I would go with erlang’s native escript instead. To build it:
1. update mix.exs, e.g. add:
escript: [main_module: MyApp, path: "bin/migrator"]
to the array returned by MyApp.Mixfile.project/0 function and add bin directory to the release:
# ⇓⇓⇓
files: ~w|bin lib mix.exs README.md|,
to the array returned by MyApp.Mixfile.package/0
2. create MyApp.main/1 function:
def main(_args) do
MyApp.ReleaseTasks.migrate
end
You are all set. There in release will be escript in bin/migrator (the name you used in step 1.)
Now you should be able to run bin/migrator, since it’s a plain old good executable.
Sidenote: mix compile would build this executable as well, so you might play with it and test it before running with distillery.