README.md

athrun

Athrun Zala, pilot of ZGMF-X19A ∞ Justice Gundam.

Pun explaination: athRuns forever (infinite)

Simple scheduler Component based on j.u.c.ScheduledThreadPoolExecutor. Supports dependency injection, multiple scheduled tasks and second resolution for repeated execution. Best of all, you can use cron expressions to configure when your handlers will execute.

It's a spiritual successor to nomnom/eternity and very simplified version of QuartzScheduler.

Installation

[athrun "0.0.3-SNAPSHOT"]

Usage

Scheduler is represented as a singular component, which manages a set of tasks. Tasks are wrapped by the component and receive the subset of the scheduler component dependencies.

Configuration

Scheduler component:

• name (just for logging)
• tasks

Tasks:

Each task requires the following:

• handler - the scheduled function, receives a map of components it depends on
• dependencies - vector of keywords to select from the scheduler component's deps
• schedule - a Cron expression, with Quartz Scheduler extension allowing for specifying schedules down to a second (UNIX Cron can only schedule up to a minute)
• name - name for logging

Simple example:

(def tasks
  [{:name "inactive-accounts"
    ;; what does this task require?
    :dependencies [:publisher :redis]
    ;; run every 5m on 0th, 5th, 10th m of hour
    :schedule "0 /5  * * * ?"
    :handler (fn [{:keys [publisher redis]}]
               (publisher :check-accounts (get-data-from redis)))}
   {:name "email-queue"
    ;; 2am UTC
    :schedule "0 0 2 * * *"
    ;; note that dependencies are pulled out of the scheduler component
    :dependencies [:publisher :db-conn]
    :handler (fn [{:keys [publisher db-conn]}]
               (store-results db-conn (publisher :send-emails)))}])


(def system
  {:scheduler (component/using
               (athrun.core/create {:name "scheduler"
                                    :scheduled-tasks tasks})
               ;; some component for pushing messages to a background job queue, redis and db clients
               ;; the scheduler component has to depend on all dependencies of its tasks
               [:publisher :redis :db-conn])})

Middlewares

Similarly to Eternity, middlewares are supported and VERY simple. There are two provided:

• athrun.middleware/with-lock - based on LockJaw require's lock component in the system and dependencies list

• athrun.middleware/with-logging - simple logger based middleware, with DEBUG logs

Usage

Define your task like so:

(def scheduled-handler
  (athrun.middleware/with-lock
    (athunr.middleware/wthi-logging
     (fn []
       (println "i'll do some work, but only if I have the lock")))))

and use it in your task definition.

Roadmap

• better docs
• more testing

License

Copyright © 2018 - 2022 Lukasz Korecki

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