Install `node_exporter` when finding a newer version.

cookbooks/prometheus/node_exporter_install.rb

@@ -1,6 +1,9 @@
 node_exporter_url = ''
 node_exporter_bin = ''
 
+tag               = ''
+vtag              = ''
+
 # Calculate the Download URL:
 begin
   require 'net/http'
@@ -21,6 +24,9 @@ rescue
   raise 'Cannot connect to http://github.com.'
 end
 
+# バージョン確認して、アップデート必要かどうか確認
+result = run_command("node_exporter --version 2>&1 | grep #{tag}", error: false)
+if result.exit_status != 0
   # Download:
   TMP = "/tmp/#{node_exporter_bin}"
 
@@ -46,3 +52,4 @@ end
   link "#{node['node_exporter']['location']}node_exporter" do
     to "#{node['node_exporter']['storage']}node_exporter"
   end
+end