Add test for reload config

Signed-off-by: Yuta Iwama <[email protected]>

lib/fluent/engine.rb

@@ -23,6 +23,7 @@
 require 'fluent/system_config'
 require 'fluent/plugin'
 require 'fluent/fluent_log_event_router'
+require 'fluent/static_config_analysis'
 
 module Fluent
   class EngineClass
@@ -166,16 +167,27 @@ def run
     def reload_config(conf, supervisor: false)
       # configure first to reduce down time while restarting
       new_agent = RootAgent.new(log: log, system_config: @system_config)
-      if (plugin = new_agent.find_unreloadable_plugin)
-        raise Fluent::ConfigError, "Unreloadable plugin: #{plugin.class}"
+      ret = Fluent::StaticConfigAnalysis.call(conf, workers: system_config.workers)
+
+      ret.all_plugins.each do |plugin|
+        if plugin.respond_to?(:reloadable_plugin?) && !plugin.reloadable_plugin?
+          raise Fluent::ConfigError, "Unreloadable plugin: #{plugin.class}"
+        end
       end
 
-      new_agent.configure(conf)
       unless @suppress_config_dump
         $log.info :supervisor, "using configuration file: #{conf.to_s.rstrip}"
       end
 
+      # Assign @root_agent to new root_agent
+      # for https://github.com/fluent/fluentd/blob/fcef949ce40472547fde295ddd2cfe297e1eddd6/lib/fluent/plugin_helper/event_emitter.rb#L50
       old_agent, @root_agent = @root_agent, new_agent
+      begin
+        @root_agent.configure(conf)
+      rescue
+        @root_agent = old_agent
+        raise
+      end
 
       # supervisor doesn't handle actual data. so the following code is unnecessary.
       if supervisor

lib/fluent/root_agent.rb

@@ -63,16 +63,6 @@ def initialize(log:, system_config: SystemConfig.new)
     attr_reader :inputs
     attr_reader :labels
 
-    def find_unreloadable_plugin
-      lifecycle do |instance|
-        if instance.respond_to?(:reloadable_plugin?) && !instance.reloadable_plugin?
-          return instance
-        end
-      end
-
-      nil
-    end
-
     def configure(conf)
       used_worker_ids = []
       available_worker_ids = (0..Fluent::Engine.system_config.workers - 1).to_a