Wraps any standard Logger class to provide tagging capabilities. Examples: 

  Logger = ActiveSupport::TaggedLogging.new(Logger.new(STDOUT))
  Logger.tagged("BCX") { Logger.info "Stuff" }                            # Logs "[BCX] Stuff"
  Logger.tagged("BCX", "Jason") { Logger.info "Stuff" }                   # Logs "[BCX] [Jason] Stuff"
  Logger.tagged("BCX") { Logger.tagged("Jason") { Logger.info "Stuff" } } # Logs "[BCX] [Jason] Stuff"

This is used by the default Rails.logger as configured by Railties to make it easy to stamp log lines with subdomains, request ids, and anything else to aid debugging of multi-user production applications.

Methods
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Class Public methods
new(logger)

Source: show | on GitHub 

    # File activesupport/lib/active_support/tagged_logging.rb, line 16
16:     def initialize(logger)
17:       @logger = logger
18:       @tags   = Hash.new { |h,k| h[k] = [] }
19:     end
Instance Public methods
add(severity, message = nil, progname = nil, &block)

Source: show | on GitHub 

    # File activesupport/lib/active_support/tagged_logging.rb, line 35
35:     def add(severity, message = nil, progname = nil, &block)
36:       message = (block_given? ? block.call : progname) if message.nil?
37:       @logger.add(severity, "#{tags_text}#{message}", progname)
38:     end
flush()

Source: show | on GitHub 

    # File activesupport/lib/active_support/tagged_logging.rb, line 49
49:     def flush
50:       @tags.delete(Thread.current)
51:       @logger.flush if @logger.respond_to?(:flush)
52:     end
method_missing(method, *args)

Source: show | on GitHub 

    # File activesupport/lib/active_support/tagged_logging.rb, line 54
54:     def method_missing(method, *args)
55:       @logger.send(method, *args)
56:     end
silence(temporary_level = Logger::ERROR, &block)

Source: show | on GitHub 

    # File activesupport/lib/active_support/tagged_logging.rb, line 30
30:     def silence(temporary_level = Logger::ERROR, &block)
31:       @logger.silence(temporary_level, &block)
32:     end
tagged(*new_tags)

Source: show | on GitHub 

    # File activesupport/lib/active_support/tagged_logging.rb, line 21
21:     def tagged(*new_tags)
22:       tags     = current_tags
23:       new_tags = Array.wrap(new_tags).flatten.reject(&:blank?)
24:       tags.concat new_tags
25:       yield
26:     ensure
27:       new_tags.size.times { tags.pop }
28:     end
Instance Protected methods
current_tags()

Source: show | on GitHub 

    # File activesupport/lib/active_support/tagged_logging.rb, line 67
67:     def current_tags
68:       @tags[Thread.current]
69:     end
tags_text()

Source: show | on GitHub 

    # File activesupport/lib/active_support/tagged_logging.rb, line 60
60:     def tags_text
61:       tags = current_tags
62:       if tags.any?
63:         tags.collect { |tag| "[#{tag}]" }.join(" ") + " "
64:       end
65:     end