private Callback<Void> securityProcessRequestCallback() {
      return buildCallback(frontendMetrics.listDatasetsSecurityProcessRequestMetrics,
          securityCheckResult -> securityService.postProcessRequest(restRequest, securityPostProcessRequestCallback()),
          uri, LOGGER, finalCallback);
    }
Start the chain by calling {@link SecurityService#preProcessRequest}.
ambry-frontend/src/main/java/com/github/ambry/frontend/ListDatasetsHandler.java