diff --git a/app/models/fluentd.rb b/app/models/fluentd.rb
index cde0640..45bc802 100644
--- a/app/models/fluentd.rb
+++ b/app/models/fluentd.rb
@@ -46,13 +46,7 @@ class Fluentd
   end
 
   def self.json_path
-    if ENV["FLUENTD_UI_DATA_DIR"].present?
-      dir = ENV["FLUENTD_UI_DATA_DIR"]
-    else
-      dir = ENV["HOME"] + "/.fluentd-ui/core_data"
-    end
-    FileUtils.mkdir_p(dir)
-    dir + "/#{Rails.env}-fluentd.json"
+    FluentdUI.data_dir + "/#{Rails.env}-fluentd.json"
   end
 
   def fluentd?
diff --git a/lib/fluentd-ui.rb b/lib/fluentd-ui.rb
index 0dcb7ef..4fd0e72 100644
--- a/lib/fluentd-ui.rb
+++ b/lib/fluentd-ui.rb
@@ -19,4 +19,10 @@ module FluentdUI
     return nil unless setup_fluentd
     setup_fluentd.agent.version
   end
+
+  def self.data_dir
+    dir = ENV["FLUENTD_UI_DATA_DIR"].presence || ENV["HOME"] + "/.fluentd-ui/core_data"
+    FileUtils.mkdir_p(dir) # ensure directory exists
+    dir
+  end
 end