```ruby
# -*- encoding: utf-8 -*-

require 'logger'

module Aliyun
  module Common
    ##
    # Logging support
    # @example
    #   include Logging
    #   logger.info(xxx)
    module Logging

      MAX_NUM_LOG = 100
      ROTATE_SIZE = 10 * 1024 * 1024

      # level = Logger::DEBUG | Logger::INFO | Logger::ERROR | Logger::FATAL
      def self.set_log_level(level)
        Logging.logger.level = level
      end

      # 设置日志输出的文件
      def self.set_log_file(file)
        @log_file = file
      end

      # 获取logger
      def logger
        Logging.logger
      end

      private

      def self.logger
        unless @logger
          # Environment parameter ALIYUN_OSS_SDK_LOG_PATH used to set output log to a file,do not output log if not set
          @log_file ||= ENV["ALIYUN_OSS_SDK_LOG_PATH"]
          @logger = Logger.new(
              @log_file, MAX_NUM_LOG, ROTATE_SIZE)
          @logger.level = Logger::INFO
        end
        @logger
      end

    end # logging
  end # Common
end # Aliyun
```

Add environment variable to set log debug output
user
```ruby
# -*- encoding: utf-8 -*-

require 'logger'

module Aliyun
  module Common
    ##
    # Logging support
    # @example
    #   include Logging
    #   logger.info(xxx)
    module Logging

      MAX_NUM_LOG = 100
      ROTATE_SIZE = 10 * 1024 * 1024

      # level = Logger::DEBUG | Logger::INFO | Logger::ERROR | Logger::FATAL
      def self.set_log_level(level)
        Logging.logger.level = level
      end

      # 设置日志输出的文件
      def self.set_log_file(file)
        @log_file = file
      end

      # 获取logger
      def logger
        Logging.logger
      end

      private

      def self.logger
        unless @logger
          # Environment parameter ALIYUN_OSS_SDK_LOG_PATH used to set output log to a file,do not output log if not set
          @log_file ||= ENV["ALIYUN_OSS_SDK_LOG_PATH"]
          @logger = Logger.new(
              @log_file, MAX_NUM_LOG, ROTATE_SIZE)
          @logger.level = get_env_log_level || Logger::INFO
        end
        @logger
      end

      def self.get_env_log_level
        return unless ENV["ALIYUN_OSS_SDK_LOG_LEVEL"]
        case ENV["ALIYUN_OSS_SDK_LOG_LEVEL"].upcase
        when "DEBUG"
          Logger::DEBUG
        when "WARN"
          Logger::WARN
        when "ERROR"
          Logger::ERROR
        when "FATAL"
          Logger::FATAL
        when "UNKNOWN"
          Logger::UNKNOWN
        end
      end

    end # logging
  end # Common
end # Aliyun
```
assistant