Create helper for easy logger creation

Author: pitr-ch

README.md

@@ -156,6 +156,8 @@ require 'concurrent/actor'          # Concurrent::Actor and supporting code
 require 'concurrent/channel '       # Concurrent::Channel and supporting code
 ```
 
+If the library does not behave as expected, `Concurrent.use_stdlib_logger(Logger::DEBUG)` could help to revel the problem.
+
 ## Installation
 
 ```shell

lib/concurrent/configuration.rb

@@ -42,6 +42,37 @@ def self.global_logger=(value)
     GLOBAL_LOGGER.value = value
   end
 
+  # @return [Logger] Logger with provided level and output.
+  def self.create_stdlib_logger(level = Logger::FATAL, output = $stderr)
+    logger           = Logger.new(output)
+    logger.level     = level
+    logger.formatter = lambda do |severity, datetime, progname, msg|
+      formatted_message = case msg
+                          when String
+                            msg
+                          when Exception
+                            format "%s (%s)\n%s",
+                                   msg.message, msg.class, (msg.backtrace || []).join("\n")
+                          else
+                            msg.inspect
+                          end
+      format "[%s] %5s -- %s: %s\n",
+             datetime.strftime('%Y-%m-%d %H:%M:%S.%L'),
+             severity,
+             progname,
+             formatted_message
+    end
+    logger
+  end
+
+  # Use logger created by #create_stdlib_logger to log concurrent-ruby messages.
+  def self.use_stdlib_logger(level = Logger::FATAL, output = $stderr)
+    logger = create_stdlib_logger level, output
+    Concurrent.global_logger = lambda do |level, progname, message = nil, &block|
+      logger.add level, message, progname, &block
+    end
+  end
+
   # Disables AtExit hooks including pool auto-termination hooks.
   # When disabled it will be the application
   # programmer's responsibility to ensure that the hooks

spec/spec_helper.rb

@@ -2,29 +2,7 @@
 require 'concurrent'
 require 'concurrent-edge'
 
-logger       = Logger.new($stderr)
-logger.level = Logger::FATAL
-
-logger.formatter = lambda do |severity, datetime, progname, msg|
-  formatted_message = case msg
-                      when String
-                        msg
-                      when Exception
-                        format "%s (%s)\n%s",
-                               msg.message, msg.class, (msg.backtrace || []).join("\n")
-                      else
-                        msg.inspect
-                      end
-  format "[%s] %5s -- %s: %s\n",
-         datetime.strftime('%Y-%m-%d %H:%M:%S.%L'),
-         severity,
-         progname,
-         formatted_message
-end
-
-Concurrent.global_logger = lambda do |level, progname, message = nil, &block|
-  logger.add level, message, progname, &block
-end
+Concurrent.use_stdlib_logger Logger::DEBUG
 
 if ENV['COVERAGE'] || ENV['CI'] || ENV['TRAVIS']
   require 'simplecov'