private void pollNewRequests(List<RequestInfo> requestsToSend, Set<Integer> requestsToDrop) {
    putManager.poll(requestsToSend, requestsToDrop);
    getManager.poll(requestsToSend, requestsToDrop);
    nonBlockingRouter.initiateBackgroundDeletes(getBackGroundDeleteRequests());
    clearBackGroundDeleteRequests();
    deleteManager.poll(requestsToSend, requestsToDrop);
    ttlUpdateManager.poll(requestsToSend, requestsToDrop);
    undeleteManager.poll(requestsToSend, requestsToDrop);
    replicateBlobManager.poll(requestsToSend, requestsToDrop);
  }
Poll for new requests from each of the operation managers, and initiate background deletes.
@param requestsToSend a list of {@link RequestInfo} that will contain the new requests to be sent out.
@param requestsToDrop a list of correlation IDs that will contain the IDs for requests that the network layer
                      should drop.
ambry-router/src/main/java/com/github/ambry/router/QuotaAwareOperationController.java