Integrant methods for running functions periodically in a thread pool. Part of the Duct framework, but can be used in any application that uses Integrant.

Add the following dependency to your deps.edn file:

org.duct-framework/scheduler.simple {:mvn/version "0.2.1"}

Or to your Leiningen project file:

[org.duct-framework/server.http.jetty "0.2.1"]

The scheduler runs jobs, which are zero-argument functions, at periodic intervals. A configuration might look something like this:

{:duct.scheduler/simple
 {:jobs [{:interval 60   :run #ig/ref :example.job/every-minute}
         {:interval 3600 :run #ig/ref :example.job/every-hour]}

 :example.job/every-minute {}
 :example.job/every-hour   {}}

Where the example jobs are defined:

(require '[integrant.core :as ig])

(defmethod ig/init-key :example.job/every-minute [_ _]
  #(println "A minute passed."))

(defmethod ig/init-key :example.job/every-hour [_ _]
  #(println "An hour passed."))

The :duct.schedule/simple key takes a collection of :jobs, and optionally the :thread-pool-size, which defaults to 32.

Jobs are maps that have three keys:

• :delay (optional) - how long in seconds to delay before the first job
• :interval - how long in seconds between the start of each job
• :run - a zero-argument function run at each interval

This scheduler isn't suitable for more complex cron-like scheduling, but is useful if you just want to periodically run cleanup, indexing or other processing scripts at regular intervals.

Copyright © 2025 James Reeves

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.