More
author |
Steve Losh <steve@stevelosh.com> |
date |
Fri, 06 Nov 2020 11:01:07 -0500 |
parents |
ff8f7c88a814 |
children |
(none) |
(eval-when (:compile-toplevel :load-toplevel :execute)
(ql:quickload
'(:adopt :iterate :external-program :parse-number :alexandria :with-user-abort)
:silent t))
(defpackage :retry
(:use :cl :iterate)
(:export :toplevel :*ui*))
(in-package :retry)
;;;; Configuration ------------------------------------------------------------
(defparameter *version* "0.0.1")
;;;; Functionality ------------------------------------------------------------
(defun backoff-immediate ()
(lambda (try) (declare (ignore try))))
(defun backoff-constant (seconds)
(lambda (try)
(declare (ignore try))
(sleep seconds)))
(defun backoff-exponential (seconds)
(lambda (try)
(sleep (* try seconds))))
(defun retry (command &key backoff tries)
(iterate
(with (program . args) = command)
(for try :from 1)
(for (values nil code) =
(external-program:run program args :input t :output t :error t))
(finding code :such-that #'zerop :on-failure 1)
(while (or (null tries) (< try tries)))
(when backoff
(funcall backoff try))))
;;;; Run ----------------------------------------------------------------------
(defun run (arguments options)
(retry (let ((shell (gethash 'shell options)))
(if shell
`("sh" "-c" ,shell)
arguments))
:tries (gethash 'tries options)
:backoff (gethash 'backoff options)))
;;;; User Interface -----------------------------------------------------------
(adopt:define-string *help*
"retry runs another command, retrying it if it returns a non-zero exit code.~@
~@
Options are available for configuring the number of retries and how long ~
to wait before retrying. If the command eventually succeeds, retry will ~
return an exit code of 0, otherwise it will return an exit code of 1.")
(adopt:define-string *help-command*
"By default, any non-option arguments to retry will designate the command ~
to be run. If the command itself has options, you'll need to use -- to tell ~
retry which options belong to the command, e.g.:~@
~@
~:
retry --backoff 5 -- ping -c 1 -w 1 example.com~@
~@
You can use the --shell option to specify the command to run as a single ~
string, which can be handy if you need to redirect its output:~@
~@
~:
retry -t5 -b1 --shell 'curl -Lsf stevelosh.com | grep -q Hello'")
(defparameter *examples*
'(("Retry flashing a cheap EEPROM a few times before giving up:"
. "retry --tries 3 -- minipro -p AT28C256 -w rom.bin")
("Try to curl a healthcheck endpoint with exponential backoff:"
. "retry --backoff 1 --tries 5 --shell \"curl -Lsf 'http://example.com/healthcheck/' >/dev/null\"")))
(defparameter *option-shell*
(adopt:make-option 'shell
:help "Execute `sh -c \"$CMD\"`, instead of passing the command as separate arguments to retry."
:long "shell"
:short #\s
:parameter "CMD"
:reduce #'adopt:last))
(defparameter *option-no-shell*
(adopt:make-option 'no-shell
:result-key 'shell
:help "Execute the non-option arguments to retry as the command (the default)."
:long "no-shell"
:short #\S
:reduce (constantly nil)))
(defparameter *option-immediate*
(adopt:make-option 'immediate
:result-key 'backoff
:help "Retry the command immediately on failure (the default)."
:long "immediate"
:short #\i
:reduce (constantly (backoff-immediate))))
(defparameter *option-wait*
(adopt:make-option 'wait
:result-key 'backoff
:help "Wait N seconds before retrying a failed command."
:long "wait"
:short #\w
:parameter "N"
:key (alexandria:compose #'backoff-constant #'parse-number:parse-number)
:reduce #'adopt:last))
(defparameter *option-backoff*
(adopt:make-option 'backoff
:result-key 'backoff
:help "Backoff (N * try) seconds before retrying a failed command."
:long "backoff"
:short #\b
:parameter "N"
:key (alexandria:compose #'backoff-exponential #'parse-number:parse-number)
:reduce #'adopt:last))
(defparameter *option-tries*
(adopt:make-option 'tries
:help "Maximum number of tries to attempt."
:long "tries"
:short #\t
:parameter "N"
:initial-value nil
:key #'parse-integer
:reduce #'adopt:last))
(defparameter *option-try-forever*
(adopt:make-option 'try-forever
:result-key 'tries
:help "Try forever (the default)."
:long "try-forever"
:short #\T
:reduce (constantly nil)))
(defparameter *option-help*
(adopt:make-option 'help
:help "Display help and exit."
:long "help"
:short #\h
:reduce (constantly t)))
(defparameter *option-version*
(adopt:make-option 'version
:help "Display version information and exit."
:long "version"
:reduce (constantly t)))
(defparameter *ui*
(adopt:make-interface
:name "retry"
:usage "[OPTIONS] -- COMMAND [ARG...]"
:summary "retry running a command"
:help *help*
:examples *examples*
:contents (list
(adopt:make-group
'tries
:title "Number of Tries"
:options (list
*option-tries*
*option-try-forever*))
(adopt:make-group
'backoff-policy
:title "Backoff Policy"
:options (list
*option-immediate*
*option-wait*
*option-backoff*))
(adopt:make-group
'command
:title "Specifying a Command"
:help *help-command*
:options (list
*option-shell*
*option-no-shell*))
*option-help*
*option-version*)))
(defun parse-options-or-exit (ui)
(handler-case (adopt:parse-options ui)
(error (c) (adopt:print-error-and-exit c))))
(defun toplevel ()
#+sbcl (sb-ext:disable-debugger)
(handler-case
(with-user-abort:with-user-abort
(multiple-value-bind (arguments options)
(parse-options-or-exit *ui*)
(cond
((gethash 'help options) (adopt:print-help-and-exit *ui*))
((gethash 'version options) (write-line *version*) (adopt:exit))
(t (adopt:exit (run arguments options))))))
(with-user-abort:user-abort () (adopt:exit 130))))