https://github.com/death/exponential-backoff.git
git clone 'https://github.com/death/exponential-backoff.git'
(ql:quickload :exponential-backoff)
An implementation of the exponential backoff algorithm in Common Lisp.
Inspired by the implementation found in Chromium. Read the header file to learn about each of the parameters.
If you like to SLEEP or otherwise block, and don't care to signal errors until giving up:
(defun noisy-sleep (seconds)
(format t "Sleeping for ~A seconds.~%" seconds)
(sleep seconds))
(exponential-backoff:with-exponential-backoff ((:initial-delay-ms 1000 :jitter-factor 0.1)
:max-retries 3 :sleep-function #'noisy-sleep)
(format t "Trying...~%")
(error "Something bad happened."))
;; Output:
;;
;; Trying...
;; Sleeping for 0.9575 seconds.
;; Trying...
;; Sleeping for 1.8265 seconds.
;; Trying...
;; Sleeping for 3.855 seconds.
;; Trying...
;; ; Evaluation aborted on #<SIMPLE-ERROR "Something bad happened." {1009EB9E83}>.A more involved example that uses the backoff information by itself:
(loop with b = (exponential-backoff:exponential-backoff
:num-failures-to-ignore 1
:initial-delay-ms (* 5 1000)
:jitter-factor 0.1
:max-backoff-ms (* 5 60 1000))
for time-to-wait = (exponential-backoff:time-until-release b)
for will-succeed in '(t nil nil nil t nil nil t t nil nil)
do (format t "Waiting for ~F ms before ~:[failing~;succeeding~]...~%" time-to-wait will-succeed)
do (sleep (/ time-to-wait 1000))
do (exponential-backoff:inform b will-succeed))
;; Output:
;;
;; Waiting for 0.0 ms before succeeding...
;; Waiting for 0.0 ms before failing...
;; Waiting for 0.0 ms before failing...
;; Waiting for 4647.0 ms before failing...
;; Waiting for 9893.5 ms before succeeding...
;; Waiting for 0.0 ms before failing...
;; Waiting for 9357.5 ms before failing...
;; Waiting for 18710.0 ms before succeeding...
;; Waiting for 0.0 ms before succeeding...
;; Waiting for 0.0 ms before failing...
;; Waiting for 9969.0 ms before failing...MIT