just so my headache is logged somewhere.

there’s two different layers you can config in the logger. one for backends, one for logger itself. so in my case this helper a lot:

config :logger, truncate: :infinity
config :logger, :console, truncate: :infinity

thanks goes to @JonRowe and @LostKobrakai in Slack.

Updates that fit the current situation:

disable log truncation

As of Elixir 1.14:

config :logger, truncate: :infinity is enough for disabling log truncation.

config :logger, :console, truncate: doesn’t exist anymore.

log data

Another point to note if you are planing to print data with inspect/2:

Logger.info( inspect(data) )

Make sure that inspect will print all the information you want. The following line is a good start:

Logger.info( inspect(data, structs: false, limit: :infinity, printable_limit: :infinity) )

performance consideration

If the data is large, carefully consider before using the above two steps.

Just for giggles I put it in a test case:

defmodule ThingTest do
  use ExUnit.Case
  import ExUnit.CaptureLog
  require Logger

  @message_size 8_000

  test "Logger backend end" do
    assert capture_log(fn -> Logger.error(String.duplicate("A", @message_size)) end) >= @message_size
  end
end

And ran the test:

kip@Kips-iMac-Pro thing % mix test
.

Finished in 0.04 seconds
1 test, 0 failures

To enable infinite truncation in the new Logger (since Elixir 1.15) do:

config :logger, :default_formatter,
  ...,
  truncate: :infinity

Is it perhaps the :truncate option? By default it’s 8kiB.

:truncate - the maximum message size to be logged (in bytes). Defaults to 8192 bytes. Note this configuration is approximate. Truncated messages will have " (truncated)" at the end. The atom :infinity can be passed to disable this behavior.