Akka Cron Demo

A simple Cron Scheduler service using Akka Actors. Underneath its using Quartz Scheduler and sends messages to actors at the scheduled intervals for processing.

Requires JDK 11 and sbt 1.3+.

Start

1. Start the Akka Http server:

$ cd akka-cron-demo
$ sbt run

Send some requests

2. Open a new terminal and send a HTTP call to the API to create a cron job.

$ curl -X POST "127.0.0.1:8080/jobs" -H "Content-Type: text/plain" --data "*/10 * * ? * *"

View the logs

3. Monitor the logs to see jobs are scheduled and trigger according to their schedule given.

[info] running com.amdelamar.App 
20:34:38.155 [INFO ] Initialized Scheduler Signaller of type: class org.quartz.core.SchedulerSignalerImpl
20:34:38.157 [INFO ] Quartz Scheduler v.2.3.2 created.
20:34:38.159 [INFO ] RAMJobStore initialized.
20:34:38.160 [INFO ] Scheduler meta-data: Quartz Scheduler (v2.3.2) 'QuartzScheduler~my-app' with instanceId 'my-app'
  Scheduler class: 'org.quartz.core.QuartzScheduler' - running locally.
  NOT STARTED.
  Currently in standby mode.
  Number of jobs executed: 0
  Using thread pool 'org.quartz.simpl.SimpleThreadPool' - with 8 threads.
  Using job-store 'org.quartz.simpl.RAMJobStore' - which does not support persistence. and is not clustered.

20:34:38.160 [INFO ] Quartz scheduler 'QuartzScheduler~my-app'
20:34:38.160 [INFO ] Quartz scheduler version: 2.3.2
20:34:38.161 [INFO ] Scheduler QuartzScheduler~my-app_$_my-app started.
[INFO] [01/23/2021 20:34:38.166] [my-app-akka.actor.default-dispatcher-5] [[QuartzScheduler~my-app]] Initialized calendars: 
20:34:38.664 [INFO ] App is running at http://localhost:8080/
20:34:41.463 [INFO ] Received cron job: Cron(d9ad67ee-03aa-4321-9d51-4952dfd14ad0,*/10 * * ? * *)
20:34:41.463 [INFO ] Received a new cron job: Cron(d9ad67ee-03aa-4321-9d51-4952dfd14ad0,*/10 * * ? * *)
[INFO] [01/23/2021 20:34:41.465] [my-app-akka.actor.default-dispatcher-6] [[QuartzScheduler~my-app]] Setting up scheduled job 'd9ad67ee-03aa-4321-9d51-4952dfd14ad0', with 'com.typesafe.akka.extension.quartz.QuartzCronSchedule@51253a19'
20:34:41.476 [INFO ] Successfully scheduled new cron job: Cron(d9ad67ee-03aa-4321-9d51-4952dfd14ad0,*/10 * * ? * *)
20:34:50.016 [INFO ] Triggered! Cron(d9ad67ee-03aa-4321-9d51-4952dfd14ad0,*/10 * * ? * *)
20:35:00.004 [INFO ] Triggered! Cron(d9ad67ee-03aa-4321-9d51-4952dfd14ad0,*/10 * * ? * *)
20:35:10.002 [INFO ] Triggered! Cron(d9ad67ee-03aa-4321-9d51-4952dfd14ad0,*/10 * * ? * *)
20:35:20.003 [INFO ] Triggered! Cron(d9ad67ee-03aa-4321-9d51-4952dfd14ad0,*/10 * * ? * *)
20:35:30.002 [INFO ] Triggered! Cron(d9ad67ee-03aa-4321-9d51-4952dfd14ad0,*/10 * * ? * *)

Our job had */10 * * ? * * so it triggers every ten seconds. You can try out with other cron expressions, using hours, days, weeks, so you can imagine real work being done in production.

Combine this code with Akka Persistence to save the cron jobs in a database and easily continue cron execution after a sudden reboot, JVM crash or power outage.