Megatest

   (else 
    (let ((res (* 50 (exp (- x targ)))))
      (cond
       ((and (> res 0)(< res 0.01)) 0.01)
       ((> res 45)                  45) ;; cap at 45 seconds
       (else res))))))

;; x input value (current number in the queue)
;; targ is the desired queue length
;;
(define (piecewise-droop-calc x targ)
  (let ((top 50))
    (cond
     ((> (- x targ) 0)
      top) ;; top off at top seconds
     ((> x (- targ top))
      (+ (* 1 (- x (- targ top)))
	 (/ (- top targ) targ)))
     (else (let ((res (/ x targ)))
	     (if (< res 0.01)
		 0.01
		 res))))))

(define (server soc)
  (print "server starting")

(define *current-delay-mutex* (make-mutex))

;; update the *current-delay* value every minute or QUEUE_CHK_DELAY seconds
(thread-start! (make-thread (lambda ()
			      (let ((delay-time (string->number (or (get-environment-variable "QUEUE_CHK_DELAY") "30"))))
				(let loop ()
				  (with-input-from-pipe 
				   cmd  ;;; my query to get queue length
				   (lambda ()
				     (let* ((val       (read))
					    (droop-val (if (number? val)(piecewise-droop-calc val queuelen) #f)))
				       ;; val is number of jobs in queue. Use a linear droop of val/40
				       (mutex-lock! *current-delay-mutex*)
				       (set! *current-delay* (or droop-val 30)) ;; (/ (or droop-val 100) 50))
				       (mutex-unlock! *current-delay-mutex*)

(let ((signature (make-signature)))
  
  (thread-start! (lambda ()
		   (thread-sleep! 60)
		   (print "Give up on waiting for the server")
		   ;; (nn-close req)
		   ;; (exit)
		   ))
  (thread-join! (thread-start! (lambda ()
				 (let-values 
				  (((delay-time msg)(get-delay signature)))
				  (print "INFO: sleeping " delay-time " seconds per request of queuefeeder server")
				  (thread-sleep! delay-time)
				  (print "INFO: done waiting, now executing requested task.")))))
  (nn-close req))

(process-execute (car cmd) (cdr cmd))