private void buildConfigUpdateTypes(Multimap<AbstractUpgradeCatalog.ConfigUpdateType, Entry<String, String>> propertiesToLog,
                                      JsonObject configJson) {
    for (AbstractUpgradeCatalog.ConfigUpdateType configUpdateType : propertiesToLog.keySet()) {
      JsonElement currentConfigUpdateType = configJson.get(configUpdateType.getDescription());
      JsonObject currentConfigUpdateTypeJsonObject = null;
      if (currentConfigUpdateType != null) {
        currentConfigUpdateTypeJsonObject = currentConfigUpdateType.getAsJsonObject();
      } else {
        currentConfigUpdateTypeJsonObject = new JsonObject();
      }
      for (Entry<String, String> property : propertiesToLog.get(configUpdateType)) {
        currentConfigUpdateTypeJsonObject.add(property.getKey(), new JsonPrimitive(property.getValue()));
      }
      configJson.add(configUpdateType.getDescription(), currentConfigUpdateTypeJsonObject);
    }
  }
Find, read, and parse the log4j.properties file.
@return the properties that were found or empty if no file was found
ambari-server/src/main/java/org/apache/ambari/server/configuration/Configuration.java