code: public static void reloadProperties() {
      synchronized (DEFAULT_PROPERTIES_LOCK) {
        // Step1: bootstrap the configuration. This is necessary because we need to resolve alluxio
        // .home (likely to be in system properties) to locate the conf dir to search for the site
        // property file.
        AlluxioProperties properties = new AlluxioProperties();
        InstancedConfiguration conf = new InstancedConfiguration(properties);
        properties.merge(System.getProperties(), Source.SYSTEM_PROPERTY);
  
        // Step2: Load site specific properties file if not in test mode. Note that we decide
        // whether in test mode by default properties and system properties (via getBoolean).
        if (conf.getBoolean(PropertyKey.TEST_MODE)) {
          conf.validate();
          sDefaultProperties = properties;
          return;
        }
  
        // we are not in test mode, load site properties
        String confPaths = conf.get(PropertyKey.SITE_CONF_DIR);
        String[] confPathList = confPaths.split(",");
        String sitePropertyFile = ConfigurationUtils
            .searchPropertiesFile(Constants.SITE_PROPERTIES, confPathList);
        Properties siteProps = null;
        if (sitePropertyFile != null) {
          siteProps = loadPropertiesFromFile(sitePropertyFile);
          sSourcePropertyFile = sitePropertyFile;
        } else {
          URL resource =
              ConfigurationUtils.class.getClassLoader().getResource(Constants.SITE_PROPERTIES);
          if (resource != null) {
            siteProps = loadPropertiesFromResource(resource);
            if (siteProps != null) {
              sSourcePropertyFile = resource.getPath();
            }
          }
        }
        properties.merge(siteProps, Source.siteProperty(sSourcePropertyFile));
        conf.validate();
        sDefaultProperties = properties;
      }
    }
docs: Reloads site properties from disk.