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at-at

Simple ahead-of-time function scheduler. Allows you to schedule the execution of an anonymous function for a point in the future.

Installation

To use the latest release, add the following to your deps.edn (Clojure CLI)

overtone/at-at {:mvn/version "1.4.65"}

or add the following to your project.clj (Leiningen)

[overtone/at-at "1.4.65"]

Basic Usage

First pull in the lib:

(require '[overtone.at-at :as at])

at-at uses ScheduledThreadPoolExecutors behind the scenes which use a thread pool to run the scheduled tasks. You therefore need create a pool before you can get going:

(def my-pool (at/mk-pool))

It is possible to pass in extra options :cpu-count, :stop-delayed? and :stop-periodic? to further configure your pool. See mk-pool's docstring for further info.

Next, schedule the function of your dreams. Here we schedule the function to execute in 1000 ms from now (i.e. 1 second):

(at/at (+ 1000 (at/now)) #(println "hello from the past!") my-pool)

You may also specify a description for the scheduled task with the optional :desc key.

Another way of achieving the same result is to use after which takes a delaty time in ms from now:

(at/after 1000 #(println "hello from the past!") my-pool)

You can also schedule functions to occur periodically. Here we schedule the function to execute every second:

(at/every 1000 #(println "I am cool!") my-pool)

This returns a scheduled-fn which may easily be stopped stop:

(at/stop *1)

Or more forcefully killed with kill.

It's also possible to start a periodic repeating fn with an initial delay:

(at/every 1000 #(println "I am cool!") my-pool :initial-delay 2000)

Finally, you can also schedule tasks for a fixed delay (vs a rate):

(at/interspaced 1000 #(println "I am cool!") my-pool)

This means that it will wait 1000 ms after the task is completed before starting the next one.

Resetting a pool.

When necessary it's possible to stop and reset a given pool:

(at/stop-and-reset-pool! my-pool)

You may forcefully reset the pool using the :kill strategy:

(at/stop-and-reset-pool! my-pool :strategy :kill)

Viewing running scheduled tasks.

at-at keeps an eye on all the tasks you've scheduled. You can get a set of the current jobs (both scheduled and recurring) using scheduled-jobs and you can pretty-print a list of these job using show-schedule. The ids shown in the output of show-schedule are also accepted in kill and stop, provided you also specify the associated pool. See the kill and stop docstrings for more information.

(def tp (at/mk-pool))
(at/after 10000 #(println "hello") tp :desc "Hello printer")
(at/every 5000 #(println "I am still alive!") tp :desc "Alive task")
(at/show-schedule tp)
;; [6][RECUR] created: Thu 12:03:35s, period: 5000ms,  desc: "Alive task"
;; [5][SCHED] created: Thu 12:03:32s, starts at: Thu 12:03:42s, desc: "Hello printer"

History

at-at was extracted from the awesome music making wonder that is Overtone (http://github.com/overtone/overtone)

Release Tooling

This project uses the Lambda Island release tooling. See bin/proj --help for options. To release a new version to Clojars:

bin/proj release

Authors

• Sam Aaron
• Jeff Rose
• Michael Neale
• Alexander Oloo
• Arne Brasseur
• Daniel MacDougall
• Josh Comer

(Ascii art borrowed from http://www.sanitarium.net/jokes/getjoke.cgi?132)

License

Copyright © 2011-2023 Sam Aaron, Jeff Rose, and contributors

Available under the terms of the Eclipse Public License 1.0, see LICENSE.txt