1 files changed, 63 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/tagged_logging.rb b/activesupport/lib/active_support/tagged_logging.rb
new file mode 100644
index 0000000000..8eae43188d
--- /dev/null
+++ b/activesupport/lib/active_support/tagged_logging.rb
@@ -0,0 +1,63 @@
+require 'active_support/core_ext/object/blank'
+require 'logger'
+
+module ActiveSupport
+  # 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.
+  class TaggedLogging
+    def initialize(logger)
+      @logger = logger
+      @tags   = Hash.new { |h,k| h[k] = [] }
+    end
+
+    def tagged(*new_tags)
+      tags     = current_tags
+      new_tags = Array.wrap(new_tags).flatten.reject(&:blank?)
+      tags.concat new_tags
+      yield
+    ensure
+      new_tags.size.times { tags.pop }
+    end
+
+    def add(severity, message = nil, progname = nil, &block)
+      @logger.add(severity, "#{tags_text}#{message}", progname, &block)
+    end
+
+    %w( fatal error warn info debug unknown ).each do |severity|
+      eval <<-EOM, nil, __FILE__, __LINE__ + 1
+        def #{severity}(progname = nil, &block)              # def warn(progname = nil, &block)
+          add(Logger::#{severity.upcase}, progname, &block)  #   add(Logger::WARN, progname, &block)
+        end                                                  # end
+      EOM
+    end
+
+    def flush
+      @tags.delete(Thread.current)
+      @logger.flush if @logger.respond_to?(:flush)
+    end
+
+    def method_missing(method, *args)
+      @logger.send(method, *args)
+    end
+
+    protected
+
+    def tags_text
+      tags = current_tags
+      if tags.any?
+        tags.collect { |tag| "[#{tag}]" }.join(" ") + " "
+      end
+    end
+
+    def current_tags
+      @tags[Thread.current]
+    end
+  end
+end