For a mix task, I can configure Logger in config.exs, but not logger console formatting. Am I doing something wrong here?

[Steffen Bauer]

I prefer to add the date in my logger outputs to the console; furthermore I want info messages in green color, so for every project I add according configuration in config.exs.

Unfortunately, I don't manage to properly configure the output in a custom mix task.

To illustrate this I just reproduced this problem with a basic setup:

a) New project with

> mix new logtest

b) Configuration file:

# config/config.exs
use Mix.Config

config :logger,
  level: :debug

config :logger, :console,
  format: "$date $time [$level] $levelpad$message\n",
  colors: [info: :green]

c) A most basic mix task:

# lib/mix/tasks/doit.ex
defmodule Mix.Tasks.Doit do
  use Mix.Task
  @shortdoc "Do something"

  def run(_args) do
    Logtest.do_something
  end

end

# lib/logtest.ex
defmodule Logtest do
  require Logger
 
  def do_something do
    Logger.info "This is an info message in the real thing"
    Logger.debug "This is a debug message in the real thing"
    Logger.warn "This is a warning message in the real thing"
    Logger.error "This is an error message in the real thing"
  end

end

d) Test file:

# test/logtest_test.exs
defmodule LogtestTest do
  use ExUnit.Case
  require Logger
 
  test "the truth" do
    Logger.info "This is an info message in a test"
    Logger.debug "This is a debug message in a test"
    Logger.warn "This is a warning message in a test"
    Logger.error "This is an error message in a test"
  end
end

Effect: When running the test, I get the expected logger output (the info message is green on my console, date is included)

> mix test

2015-10-27 13:46:23.368 [info]  This is an info message in a test
.

2015-10-27 13:46:23.368 [debug] This is a debug message in a test
2015-10-27 13:46:23.368 [warn]  This is a warning message in a test
Finished in 0.05 seconds (0.05s on load, 0.00s on tests)
2015-10-27 13:46:23.368 [error] This is an error message in a test
1 test, 0 failures

But not when I run the mix task (it shows default formatting, and the info messages are in black color as default console color):

> mix doit

13:59:12.637 [info]  This is an info message in the real thing

13:59:12.638 [debug] This is a debug message in the real thing

13:59:12.638 [warn]  This is a warning message in the real thing

13:59:12.638 [error] This is an error message in the real thing

When for example I change the logging level in config.exs to :warn, running > mix doit will only show warn and error messages as expected, while still ignoring my console format configuration. So config.exs is definitely used for logger configuration in my mix task, but it ignores the 'config :logger, :console' part

No changes in mix.exs. Elixir 1.1.1, Erlang OTP 17.5. Linux Debian 8 'Jessie'

Am I doing something fundamentally wrong? It might be only a minor problem, but I am struggling with this for days now. Googled a lot and searched here for similiar problems, found nothing so far.

[José Valim]

Steffen, it sounds like it should just work. Can you push a simple app to Github? I'd gladly take a look.

José Valim

www.plataformatec.com.br

Skype: jv.ptec

Founder and Director of R&D

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[Steffen Bauer]

Hi José,

thanks a lot for having a look. I just pushed the basic example project onto GitHub under:

https://github.com/SteffenBauer/elixir-logtest

[Theron Boerner]

Do you have any other files in config like dev.exs, test.exs, or
prod.exs? They may be messing with the settings.

[Steffen Bauer]

No other files at all.

I posted the example to:

https://github.com/SteffenBauer/elixir-logtest

I double-re-checked it, I just checked out this repository, compiled it with 'mix compile', then both 'mix test' and 'mix doit'. The test run is showing the desired logger formatting on my machine, the doit task is showing default logger formatting ignoring my configuration.

[José Valim]

The reason is that the Logger application is restarted when you start your application but not before. So the configuration is loaded but it takes no effect until Mix.Task.run "app.start" is called (which the test task does). If your mix task is meant to be called inside an application, you can add Mix.Task.run "app.start" to it, otherwise, you can't really configure Logger for a custom/bare task.

José Valim

www.plataformatec.com.br

Skype: jv.ptec

Founder and Director of R&D

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[Steffen Bauer]

Hi José,

that worked! Thanks a lot!

My code now looks like this:

# lib/logtest.ex
defmodule Logtest do

  use Application
  require Logger
 
  def start(_type, _args) do
  end

 
  def do_something do
    Logger.info "This is an info message in the real thing"
    Logger.debug "This is a debug message in the real thing"
    Logger.warn "This is a warning message in the real thing"
    Logger.error "This is an error message in the real thing"
  end

end

# lib/mix/tasks/doit.ex
defmodule Mix.Tasks.Doit do
  use Mix.Task
  @shortdoc "Do something"

  def run(_args) do

    Mix.Task.run "app.start"
    Logtest.do_something
  end

end

[José Valim]

Great! Btw, you don't need use Application and def start, only if you have a supervision tree (which in your case you do not!).

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