title: Use ignore_unavailable parameter in ElasticSearch Java client
body: <p>I'm using ElasticSearch java client as a Maven dependency:</p>
  
  <pre><code>    &lt;dependency&gt;
          &lt;groupId&gt;org.elasticsearch&lt;/groupId&gt;
          &lt;artifactId&gt;elasticsearch&lt;/artifactId&gt;
          &lt;version&gt;1.7.1&lt;/version&gt;
      &lt;/dependency&gt;
  </code></pre>
  
  <p>I am doing search with multi-index, and I'm getting <code>IndexMissingException</code> and I want to ignore it using the parameter: '<strong>ignore_unavailable</strong>' but I don't know how to use it, and don't found documentation about this.</p>
  
  <p><a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/multi-index.html" rel="nofollow">https://www.elastic.co/guide/en/elasticsearch/reference/current/multi-index.html</a> (link about ignore_unavailable)</p>
  
  <p>I'm creating the search like this:</p>
  
  <pre><code>    SearchRequestBuilder srb = ess.getClient()
          .prepareSearch(generateIndex(query)) //generateIndex returns a array
          .setTypes("mytype")
          .setSearchType(SearchType.DFS_QUERY_AND_FETCH)
          .setPostFilter(FilterBuilders.rangeFilter("Time")
                  .from(time1.toInstant(ZoneOffset.UTC))
                  .to(time2.toInstant(ZoneOffset.UTC))
          )   
          .setFrom(0).setSize(RESULT_MAX).setExplain(true)
          //putHeader don't work...
         .putHeader("ignore_unavailable", true);   
  </code></pre>
  
  <p><strong>How do I use ignore_unavalilable here?</strong></p>