Форматирование логов

config.exs

.....
config :logger, :console,
  level: :debug,
  format: {LoggerFormatter, :format_log}, 

logger_formatter.ex

defmodule LoggerFormatter do
  
  @moduledoc false
  @doc """
    function formats logger message
  """
  def format_log(level, message, timestamp, metadata) do
    [module_name, {:pid, pid}] = metadata
    "#{timestamp_to_string(timestamp)} [#{inspect pid}] [#{level}] #{message_to_string_with_limit(message)}\n"
  end

  @doc """
    by default string's length = 1500 symbols
    if string is lonпer, then after 1500 symbols adds "... (total length 3218)"
  """
  def message_to_string_with_limit(message, length \\ 1500) do
    str_msg = to_string message 
    additional_text = case String.length(str_msg) > length do
      :true  -> "... (total length #{String.length(str_msg)})"
      :false -> ""
    end
    str_msg = String.replace(str_msg, "\n", "\\n")
    String.slice(str_msg, 0..length) <> additional_text
  end

  @doc """
    transforms logger timestamps to string
  """
  def timestamp_to_string(timestamp) do
    {date_tuple, time_tuple_wth_ms} = timestamp
    "#{format_date(date_tuple)} #{format_time(time_tuple_wth_ms)}"
  end

  # logger's default functions
  defp pad2(int) when int < 10, do: [?0, Integer.to_string(int)]
  defp pad2(int), do: Integer.to_string(int)
  defp pad3(int) when int < 10, do: [?0, ?0, Integer.to_string(int)]
  defp pad3(int) when int < 100, do: [?0, Integer.to_string(int)]
  defp pad3(int), do: Integer.to_string(int)

  def format_date({yy, mm, dd}) do
    [Integer.to_string(yy), ?-, pad2(mm), ?-, pad2(dd)]
  end

  def format_time({hh, mi, ss, ms}) do
    [pad2(hh), ?:, pad2(mi), ?:, pad2(ss), ?., pad3(ms)]
  end
end