void ensureZeppelinProxyUserConfigs() throws AmbariException {
    Clusters clusters = injector.getInstance(Clusters.class);
    Map<String, Cluster> clusterMap = getCheckedClusterMap(clusters);

    if ((clusterMap != null) && !clusterMap.isEmpty()) {
      for (final Cluster cluster : clusterMap.values()) {
        Config zeppelinEnvConfig = cluster.getDesiredConfigByType("zeppelin-env");

        if (zeppelinEnvConfig != null) {
          // If zeppelin-env exists, than it is assumed that Zeppelin is installed
          Map<String, String> zeppelinEnvProperties = zeppelinEnvConfig.getProperties();

          String zeppelinUser = null;
          if (zeppelinEnvProperties != null) {
            zeppelinUser = zeppelinEnvProperties.get("zeppelin_user");
          }

          if (!StringUtils.isEmpty(zeppelinUser)) {
            // If the zeppelin user is set, see if the proxyuser configs need to be set

            Config coreSiteConfig = cluster.getDesiredConfigByType(CORE_SITE);
            if (coreSiteConfig != null) {
              // If core-site exists, ensure the proxyuser configurations for Zeppelin are set.
              // If they are not already set, set them to their default value.
              String proxyUserHostsName = String.format("hadoop.proxyuser.%s.hosts", zeppelinUser);
              String proxyUserGroupsName = String.format("hadoop.proxyuser.%s.groups", zeppelinUser);

              Map<String, String> proxyUserProperties = new HashMap<>();
              proxyUserProperties.put(proxyUserHostsName, "*");
              proxyUserProperties.put(proxyUserGroupsName, "*");

              Map<String, String> coreSiteConfigProperties = coreSiteConfig.getProperties();

              if (coreSiteConfigProperties != null) {
                if (coreSiteConfigProperties.containsKey(proxyUserHostsName)) {
                  proxyUserProperties.remove(proxyUserHostsName);
                }

                if (coreSiteConfigProperties.containsKey(proxyUserGroupsName)) {
                  proxyUserProperties.remove(proxyUserGroupsName);
                }
              }

              if (!proxyUserProperties.isEmpty()) {
                updateConfigurationPropertiesForCluster(cluster, CORE_SITE, proxyUserProperties, true, false);
              }
            }
          }
        }
      }
    }
  }
If Zeppelin is installed, ensure that the proxyuser configurations are set in <code>core-site</code>.
<p>
The following configurations will be added, if core-site exists and the properties are not in the
set of core-site properties:
<ul>
<li><code>"hadoop.proxyuser.{zeppelin-env/zeppelin_user}.groups": "*"</code></li>
<li><code>"hadoop.proxyuser.{zeppelin-env/zeppelin_user}.hosts": "*"</code></li>
</ul>
ambari-server/src/main/java/org/apache/ambari/server/upgrade/UpgradeCatalog260.java