diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 990dff9..16a0f1f 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -27,9 +27,7 @@ class ApplicationController < ActionController::Base
   end
 
   def installing_gems
-    Plugin::WORKING.find_all do |data|
-      data[:type] == :install && data[:state] == :running
-    end.map{|data| data[:plugin]}
+    Plugin.installing
   end
 
   def uninstalling_gem?
@@ -37,9 +35,7 @@ class ApplicationController < ActionController::Base
   end
 
   def uninstalling_gems
-    Plugin::WORKING.find_all do |data|
-      data[:type] == :uninstall && data[:state] == :running
-    end.map{|data| data[:plugin]}
+    Plugin.uninstalling
   end
 
   private
diff --git a/app/models/plugin.rb b/app/models/plugin.rb
index 2a752a9..a27829e 100644
--- a/app/models/plugin.rb
+++ b/app/models/plugin.rb
@@ -100,6 +100,20 @@ class Plugin
     end
   end
 
+  def self.processing
+    WORKING.find_all do |data|
+      data[:state] == :running
+    end
+  end
+
+  def self.installing
+    processing.find_all{|data| data[:type] == :install }.map{|data| data[:plugin] }
+  end
+
+  def self.uninstalling
+    processing.find_all{|data| data[:type] == :uninstall }.map{|data| data[:plugin] }
+  end
+
   def self.gemfile_path
     Rails.root + "Gemfile.plugins"
   end
@@ -129,11 +143,21 @@ class Plugin
   end
 
   def gem_install
+    data = { plugin: self, state: :running, type: :install }
+    return if WORKING.grep(data).present?
+    WORKING.push(data)
     fluent_gem("install", gem_name, "-v", version)
+  ensure
+    WORKING.delete(data)
   end
 
   def gem_uninstall
+    data = { plugin: self, state: :running, type: :uninstall }
+    return if WORKING.grep(data).present?
+    WORKING.push(data)
     fluent_gem("uninstall", gem_name, "-x", "-a")
+  ensure
+    WORKING.delete(data)
   end
 
   def fluent_gem(*commands)
diff --git a/app/workers/gem_installer.rb b/app/workers/gem_installer.rb
index 826d0fa..3a9991d 100644
--- a/app/workers/gem_installer.rb
+++ b/app/workers/gem_installer.rb
@@ -5,16 +5,8 @@ class GemInstaller
   def perform(gem_name, version = nil)
     SuckerPunch.logger.info "install #{gem_name} #{version}"
     pl = Plugin.new(gem_name: gem_name, version: version)
-    data = { plugin: pl, type: :install, state: :running }
-    if Plugin::WORKING.grep(data).blank?
-      Plugin::WORKING.push(data)
-      begin
-        pl.uninstall! if pl.installed?
-        pl.install!
-      ensure
-        Plugin::WORKING.delete(data)
-      end
-    end
+    pl.uninstall! if pl.installed?
+    pl.install!
     SuckerPunch.logger.info "installed #{gem_name} #{version}"
   end
 end
diff --git a/app/workers/gem_uninstaller.rb b/app/workers/gem_uninstaller.rb
index d5d4f8d..c51d73c 100644
--- a/app/workers/gem_uninstaller.rb
+++ b/app/workers/gem_uninstaller.rb
@@ -5,15 +5,7 @@ class GemUninstaller
   def perform(gem_name)
     SuckerPunch.logger.info "uninstall #{gem_name}"
     pl = Plugin.new(gem_name: gem_name)
-    data = { plugin: pl, type: :uninstall, state: :running }
-    if Plugin::WORKING.grep(data).blank?
-      Plugin::WORKING.push(data)
-      begin
-        pl.uninstall!
-      ensure
-        Plugin::WORKING.delete(data)
-      end
-    end
+    pl.uninstall!
     SuckerPunch.logger.info "uninstalled #{gem_name}"
   end
 end