public String getTimelineServerUrl() {
    String url = context.getCluster() != null ? getATSUrlFromCluster() : getATSUrlFromCustom();
    return removeTrailingSlash(url);
  }
@return The timeline server url. If the view instance is cluster associated, the value is taken from the
yarn-site.xml else it is retrieved from the view configuration.
contrib/views/utils/src/main/java/org/apache/ambari/view/utils/ambari/Services.java