Ruby pattern for including a logging module everywhere you want. Just add “include Logging” at the top and you get both class and instance methods for logging such as #info, #debug, #error, #warn, #fatal. The threading at the bottom shows that the Logger is thread-safe and can be used without Mutexes.

logging_module.rb

# (c) 2024 Konstantin Gredeskoul
# Under the MIT License 
#
# This gist documents a frequently thed pattern of decorating multiple classes with Logging methods 
# by sharing just one Logger typically at the top of the module namespace (Application) in this case.

# If the concurrency issues come up, each class can be given its own logger, or perhaps the Logging moduloe
# might have decorators for each of the logging methods (eg #info, #debug) by using a Mutex.
#
# The output of this Ruby Code should be as follows:
# 
# I, [2024-07-30T19:00:40.887991 #1]  INFO -- : Appplication Starting
# I, [2024-07-30T19:00:40.889128 #1]  INFO -- : CLASS    | TestClass [ $TestClass ] finished loading
# I, [2024-07-30T19:00:40.889204 #1]  INFO -- : INSTANCE | TestClass [ #<TestClass:0x00007f7e093cd3c0> ] : #initialize
# E, [2024-07-30T19:00:40.889245 #1] ERROR -- : CLASS    | TestClass [ main | logging
# I, [2024-07-30T19:00:40.994221 #1]  INFO -- : Thread 1
# I, [2024-07-30T19:00:40.994387 #1]  INFO -- : Thread 27
# I, [2024-07-30T19:00:40.994444 #1]  INFO -- : Thread 28
# I, [2024-07-30T19:00:40.994492 #1]  INFO -- : Thread 15
# I, [2024-07-30T19:00:40.994569 #1]  INFO -- : Thread 5
# I, [2024-07-30T19:00:40.994697 #1]  INFO -- : Thread 4
# I, [2024-07-30T19:00:40.994755 #1]  INFO -- : Thread 0
# I, [2024-07-30T19:00:40.994874 #1]  INFO -- : Thread 23
# I, [2024-07-30T19:00:40.994952 #1]  INFO -- : Thread 24
# I, [2024-07-30T19:00:40.995027 #1]  INFO -- : Thread 37
# I, [2024-07-30T19:00:40.995076 #1]  INFO -- : Thread 35
# I, [2024-07-30T19:00:40.995130 #1]  INFO -- : Thread 7
# I, [2024-07-30T19:00:40.995177 #1]  INFO -- : Thread 30
# I, [2024-07-30T19:00:40.995541 #1]  INFO -- : Thread 6
# I, [2024-07-30T19:00:40.995859 #1]  INFO -- : Thread 33
# I, [2024-07-30T19:00:40.995938 #1]  INFO -- : Thread 36
# I, [2024-07-30T19:00:40.995988 #1]  INFO -- : Thread 34
# I, [2024-07-30T19:00:40.997059 #1]  INFO -- : Thread 12
# I, [2024-07-30T19:00:40.997150 #1]  INFO -- : Thread 8
# I, [2024-07-30T19:00:40.997210 #1]  INFO -- : Thread 10
# I, [2024-07-30T19:00:40.997253 #1]  INFO -- : Thread 14
# I, [2024-07-30T19:00:40.997295 #1]  INFO -- : Thread 21
# I, [2024-07-30T19:00:40.997338 #1]  INFO -- : Thread 16
# I, [2024-07-30T19:00:40.997379 #1]  INFO -- : Thread 20
# I, [2024-07-30T19:00:40.997418 #1]  INFO -- : Thread 19
# I, [2024-07-30T19:00:40.997492 #1]  INFO -- : Thread 18
# I, [2024-07-30T19:00:40.997538 #1]  INFO -- : Thread 17
# I, [2024-07-30T19:00:40.997588 #1]  INFO -- : Thread 22
# I, [2024-07-30T19:00:40.997631 #1]  INFO -- : Thread 13
# I, [2024-07-30T19:00:40.997706 #1]  INFO -- : Thread 3
# I, [2024-07-30T19:00:40.998416 #1]  INFO -- : Thread 32
# I, [2024-07-30T19:00:40.998491 #1]  INFO -- : Thread 26
# I, [2024-07-30T19:00:40.998559 #1]  INFO -- : Thread 29
# I, [2024-07-30T19:00:40.998644 #1]  INFO -- : Thread 38
# I, [2024-07-30T19:00:40.998686 #1]  INFO -- : Thread 31
# I, [2024-07-30T19:00:40.998766 #1]  INFO -- : Thread 2
# I, [2024-07-30T19:00:40.998819 #1]  INFO -- : Thread 25
# I, [2024-07-30T19:00:40.998861 #1]  INFO -- : Thread 11
# I, [2024-07-30T19:00:40.998902 #1]  INFO -- : Thread 9
# I, [2024-07-30T19:00:40.998982 #1]  INFO -- : Thread 39

require 'forwardable'
require 'logger'

# Lets clear the screen 
puts `reset` rescue nil

module Application
  class << self
    attr_accessor :logger
  end
end

Application.logger = ::Logger.new($stdout)

Application.logger.info("Appplication Starting\n")

module Application
  # Globals such as the logger
  module Logging
    module InstanceMethods

      extend Forwardable
      
      def_delegators :logger, :debug, :info, :warn, :error, :fatal
      
      def logger
        ::Application.logger
      end
    end

    class << self
      def included(base)
        base.include(InstanceMethods)
        base.extend(InstanceMethods)
      end
    end
  end
end

# This is our test clienbt
class TestClass
  include Application::Logging

  def initialize
    info("INSTANCE | TestClass [ #{self} ] : #initialize")
  end

  # And at the class level
  info("CLASS    | TestClass [ $#{self} ] finished loading")
end

# This shoulod print the instance logger
instance = TestClass.new

# This should print the class level error
TestClass.error("CLASS    | TestClass [ #{self} | logging")

if (instance.logger != TestClass.logger) ||
   (TestClass.logger != Application.logger) ||
   (TestClass.logger.nil? || instance.logger.nil?)

  raise(ArgumentError, "The loggers are not identical.")
end

require 'thread'

threads = []

 40.times do |index|
  threads << Thread.new do 
    sleep 0.1
    instance.info("Thread #{index}")
  end
end

threads.each(&:join)