Configuration Example 2 (Replicated Mode)

Running a Custom Cronjob with Swarm Cronjob

This guide demonstrates how to set up a cronjob using Swarm Cronjob. The example focuses on running a task periodically based on a defined schedule.

Prerequisites

• Swarm Cronjob instance is already up and running.

Step 1: Create a Docker Compose YAML

Create a Docker Compose file to define the cronjob:

version: "3.2"

services:
  test:
    image: busybox
    command: date
    deploy:
      mode: replicated
      replicas: 0
      labels:
        - "swarm.cronjob.enable=true"
        - "swarm.cronjob.schedule=* * * * *"
        - "swarm.cronjob.skip-running=false"
      restart_policy:
        condition: none

Step 2: Deploy the Stack

Deploy the stack to your Docker Swarm cluster:

docker stack deploy -c test.yml test

Explanation of Configuration

• command: Runs the task defined by the command field (in this case, the date command).
• mode: replicated: Ensures the task runs only when scheduled.
• replicas: 0: Prevents the task from running immediately upon deployment.
• swarm.cronjob.schedule=* * * * *: Schedules the task to run every minute.
• restart_policy.condition=none: Ensures the task does not restart automatically after completion.

Logs

Check the logs to verify task execution:

docker service logs swarm_cronjob_app

Example Logs:

swarm_cronjob_app.1.nvsjbhdhiagl@default    | Thu, 13 Dec 2018 20:04:37 UTC INF Starting swarm-cronjob v1.2.0
swarm_cronjob_app.1.nvsjbhdhiagl@default    | Thu, 13 Dec 2018 20:04:37 UTC INF Add cronjob with schedule * * * * * service=test
swarm_cronjob_app.1.nvsjbhdhiagl@default    | Thu, 13 Dec 2018 20:05:00 UTC INF Start job last_status=n/a service=test
swarm_cronjob_app.1.nvsjbhdhiagl@default    | Thu, 13 Dec 2018 20:06:00 UTC INF Start job last_status=n/a service=test
swarm_cronjob_app.1.nvsjbhdhiagl@default    | Thu, 13 Dec 2018 20:07:00 UTC INF Start job last_status=n/a service=test
swarm_cronjob_app.1.nvsjbhdhiagl@default    | Thu, 13 Dec 2018 20:08:00 UTC INF Start job last_status=n/a service=test

Once deployed, the cronjob will execute the defined task at the specified schedule.