private void start() {
      try {
        accountAndContainerInjector.injectAccountContainerForNamedBlob(restRequest,
            frontendMetrics.s3MultipartAbortMetricsGroup);
        restRequest.getMetricsTracker()
            .injectMetrics(
                frontendMetrics.s3MultipartAbortMetricsGroup.getRestRequestMetrics(restRequest.isSslUsed(), false));
        securityService.processRequest(restRequest, securityProcessRequestCallback());
      } catch (Exception e) {
        finalCallback.onCompletion(null, e);
      }
    }
Start the chain by calling {@link SecurityService#processRequest}.
ambry-frontend/src/main/java/com/github/ambry/frontend/s3/S3MultipartAbortUploadHandler.java