Add TaggedLogging support

Code grabbed from graylog-labs#81

Signed-off-by: Adam Tharani <[email protected]>

lib/gelf/logger.rb

@@ -2,7 +2,7 @@ module GELF
   # Methods for compatibility with Ruby Logger.
   module LoggerCompatibility
 
-    attr_accessor :formatter
+    attr_accessor :formatter, :log_tags
 
     # Use it like Logger#add... or better not to use at all.
     def add(level, message = nil, progname = nil, &block)
@@ -28,9 +28,14 @@ def add(level, message = nil, progname = nil, &block)
         message_hash.merge!(self.class.extract_hash_from_exception(message))
       end
 
-      if message_hash.key?('short_message') && !message_hash['short_message'].empty?
-        notify_with_level(level, message_hash)
+      return if !message_hash.key?('short_message') || message_hash['short_message'].empty?
+
+      # Include tags in message hash
+      Array(log_tags).each_with_index do |tag_name, index|
+        message_hash.merge!("_#{tag_name}" => current_tags[index]) if current_tags[index]
       end
+
+      notify_with_level(level, message_hash)
     end
 
     # Redefines methods in +Notifier+.
@@ -51,12 +56,37 @@ def add(level, message = nil, progname = nil, &block)
     def <<(message)
       notify_with_level(GELF::UNKNOWN, 'short_message' => message)
     end
+
+    def tagged(*tags)
+      new_tags = push_tags(*tags)
+      yield self
+    ensure
+      current_tags.pop(new_tags.size)
+    end
+
+    def push_tags(*tags)
+      tags.flatten.reject { |t| t.respond_to?(:empty?) ? !!t.empty? : !t }.tap do |new_tags|
+        current_tags.concat new_tags
+      end
+    end
+
+    def current_tags
+      val = Thread.current.thread_variable_get(:gelf_tagged_logging_tags)
+      return val unless val.nil?
+      Thread.current.thread_variable_set(:gelf_tagged_logging_tags, [])
+    end
   end
 
   # Graylog2 notifier, compatible with Ruby Logger.
   # You can use it with Rails like this:
   #     config.logger = GELF::Logger.new("localhost", 12201, "WAN", { :facility => "appname" })
   #     config.colorize_logging = false
+  #
+  # Tagged logging (with tags from rack middleware) (order of tags is important)
+  # Adds custom gelf messages: { '_uuid_name' => <uuid>, '_remote_ip_name' => <remote_ip> }
+  #     config.logger = GELF::Logger.new("localhost", 12201, "LAN", { :facility => "appname" })
+  #     config.log_tags = [:uuid, :remote_ip]
+  #     config.logger.log_tags = [:uuid_name, :remote_ip_name] # Same order as config.log_tags
   class Logger < Notifier
     include LoggerCompatibility
   end