WIP: Overhaul some behaviors of this gem

1. You should be able to set `enabled=false` and that means you will not
   log anything. Period.
2. You should be able to set `enabled=true` with
   `silence_standard_logging=true` and it will not include any of the
   log subscriber code, but it will allow you to log anything custom.
3. You should be able to recreate existing behavior with a different
   configuration. Example:
   ```
   # directly updating code
   ::LogStasher.logger = ::Logger.new(
     ::Rails.root.join("log", "logstash_#{Rails.env}.log"))

   # via the device factory
   device = ::LogStasher::Device::Factory(type: :file, path:
     ::Rails.root.join("log", "logstash_#{Rails.env}.log"))
   ::LogStasher.logger = ::Logger.new(device)
   ```

NOTE: This is a breaking change, but it might make default behaviors
easier to understand. Right now when `enable=false` it causes logs to be
piped to the logstash log file for rails apps, and that seems very
awkward. Maybe this is worth fixing?

lib/logstasher.rb

@@ -1,8 +1,10 @@
-require 'logger'
-require 'logstash-event'
+require "logger"
+require "logstash-event"
 
 module LogStasher
   class << self
+    SILENT_LOGGER = ::Logger.new("/dev/null", level: :unknown)
+
     attr_reader :append_fields_callback
     attr_writer :enabled
     attr_writer :include_parameters
@@ -61,6 +63,9 @@ def log_as_json(payload, as_logstash_event: false)
     end
 
     def logger
+      # Return a /dev/null logger if logstasher is enabled or silencing was enabled.
+      return SILENT_LOGGER if !enabled? || silence_standard_logging?
+
       @logger ||= initialize_logger
     end
 
@@ -78,4 +83,4 @@ def silence_standard_logging?
   end
 end
 
-require 'logstasher/railtie' if defined?(Rails)
+require "logstasher/railtie" if defined?(Rails)

lib/logstasher/device.rb

@@ -16,6 +16,8 @@ def self.factory(config)
         ::LogStasher::Device::UDP.new(config)
       when "stdout", :stdout then
         $stdout
+      when "file", :file then
+        config["path"]
       else
         fail ArgumentError, "Unknown type: #{type}"
       end

lib/logstasher/railtie.rb

@@ -16,45 +16,20 @@ class Railtie < ::Rails::Railtie
       ::LogStasher.include_parameters       = options.include_parameters
       ::LogStasher.serialize_parameters     = options.serialize_parameters
       ::LogStasher.silence_standard_logging = options.silence_standard_logging
-      ::LogStasher.logger                   = options.logger || default_logger
+      ::LogStasher.logger                   = options.logger
       ::LogStasher.logger.level             = options.log_level
       ::LogStasher.metadata                 = options.metadata
     end
 
-    initializer 'logstasher.load' do
-      if ::LogStasher.enabled?
+    config.after_initialize do
+      if ::LogStasher.enabled? && !::LogStasher.silence_standard_logging?
         ::ActiveSupport.on_load(:action_controller) do
-          require 'logstasher/log_subscriber'
-          require 'logstasher/context_wrapper'
+          require "logstasher/log_subscriber"
+          require "logstasher/context_wrapper"
 
           include ::LogStasher::ContextWrapper
         end
       end
     end
-
-    config.after_initialize do
-      if ::LogStasher.enabled? && ::LogStasher.silence_standard_logging?
-        require 'logstasher/silent_logger'
-
-        ::Rails::Rack::Logger.send(:include, ::LogStasher::SilentLogger)
-
-        ::ActiveSupport::LogSubscriber.log_subscribers.each do |subscriber|
-          if subscriber.is_a?(::ActiveSupport::LogSubscriber)
-            subscriber.class.send(:include, ::LogStasher::SilentLogger)
-          end
-        end
-      end
-    end
-
-    def default_logger
-      unless @default_logger
-        path = ::Rails.root.join('log', "logstash_#{::Rails.env}.log")
-        ::FileUtils.touch(path) # prevent autocreate messages in log
-
-        @default_logger =  ::Logger.new(path)
-      end
-
-      @default_logger
-    end
   end
 end