Erlang start application in production

Question

When I'm testing my erlang application on localhost, I have a script that starts the server that looks like the following:

#!/bin/sh
PWD="$(pwd)"
NAME="$(basename $PWD)"
erl -pa "$PWD/ebin" deps/*/ebin -boot start_sasl \
    -name [email protected] \
    -s reloader \
    -s $NAME \
    -setcookie some_random_cookie \
    +K true \
    +P 65536 

This prompts open the Erlang shell and from there I would type something like:

application:start(myapp)

This is fine for development purposes, but how do I deploy this in production? As of right now, the only way I can think of doing this is by starting a screen process and detaching from it. I don't think that should be the case. I am using rebar, if that helps at all.

Narcosis

Answer 1

Sounds like you want to use a custom boot script. A boot script tells the erlang system what to start. In the script you're using, you're setting the boot script with:

-boot start_sasl

http://www.erlang.org/doc/system_principles/system_principles.html, look for the section "User-Defined Boot Scripts"

An easier option may be to convert your application to use rebar: https://github.com/basho/rebar. You would then be able to do the following:

./rebar compile generate

This will create a release for the application, allowing you to then:

./rel/<app_name>/bin/<app_name>

Same principles, just all wrapped up for easy use.

Least

Note that he already mentions that rebar is being used. Your answer would be a lot better if you explained how to write a rebar reltool.config. – Ironsmith

Answer 2

Add the parameter -detached. The documentation summarizes this nicely:

Starts the Erlang runtime system detached from the system console. Useful for running daemons and backgrounds processes.

Once you do that, you can get your application to start with the -s parameter. Assuming $NAME = myapp, init will attempt to call myapp:start/0 (you can customize this if you want). That function should end with a call to application:start(myapp).

If you can get all of those puzzle pieces in place, you should have a working script.

Kerplunk

Answer 3

Well, you could try hooking it in to Apache (see here), or a simple solution that's not quite as hacky as screen sessions is to use nohup. If you're actually implementing this on a production server, and don't want to take the Apache route, you might consider an init script.

Carlina

What does Apache have to do with anything here? My Erlang nodes do not run a web server. – Narcosis

Ah, based on the information you provided to the script I assumed it was behaving as a webserver, but I guess it could also just be interacting with another web server. In that case apache is less helpful ;) nohup is still a good solution, although using the -detached option as otherwise mentioned is probably better. – Carlina

-1. A confusing answer. Apache has nothing to do with it, and nohup is not necessary for a detached erlang node. – Ironsmith