title: Elasticsearch update index template
body: <p>I have a question about elasticsearch index template, there is a scene of my question.</p>
  
  <p>Create a template for a series indices, named <code>templateA</code>, and there are some indices create from this template, named <code>Index-yyyy.mm.dd2</code> and <code>Index-yyyy.mm.dd2</code>. After a period of time, I need create some new fields in indice, and I update the <code>templateA</code>.</p>
  
  <p>SO, How to make the previously created indices use the new template? please give me some suggestion. Thanks a lot!</p>