Managing Log files with distillery

Question

Background

Using distillery to start an OTP App, I noticed that all the logs go to the ./var/log/ folder to 2 different files:

• erlang.log.1
• run_erl.log

Problems

I have issues here:

1. I don’t know what run_erl.log is supposed to log
2. I would like to change the default log path from ./var/log/erlang.log.1 to ./log/myapp.log

Research

I have checked this discussion for some hints, but according to it I have to change the configurations on the :logger extra app.

Log files in Distillery releases

This search led me to the following code snippet which uses :logger_file_backend

https://snippets.aktagon.com/snippets/773-logging-to-a-file-with-elixir

However I think I am chasing a wild goose here. I don’t think that the solution to my problem lies in adding more dependencies, but rather in changing some configuration for the :logger app.

I just don’t know where nor how.

How can I do it?

Answer 1

Are you using bin/your_app start to start your application? In that case perhaps RUNNER_LOG_DIR is a variable you're looking for to customize the log output directory.

I did a small research and noticed the issue "how to configure the path of the run_erl (for erlang.log.X, run_erl.log files)" that is similar to yours. RUNNER_LOG_DIR is mentioned during the discussion.

distillery, in turn, lists RUNNER_LOG_DIR as a configurable environment variable. It is then used when starting your application here.

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I don’t know what run_erl.log is supposed to log.

Per official Erlang documentation, run_erl.log is used to log progress and warnings from the run_erl program itself. run_erl is a program that starts the application.

I would like to change the default log path from ./var/log/erlang.log.1 to ./log/myapp.log.

Per my findings it should be possible to change the location of the log files, but I'm yet to see if it is possible to change the name of the file too (erlang.log.1 -> myapp.log), if that's also what you are asking. If you really need to change the name of the file, I'd look into symlinking myapp.log and erlang.log.1.