Use swarm-cronjob to launch Gantry at a specific time.
In this example, we only want to run Gantry at the specific time, therefore we set replicas to 0 on the Gantry service to avoid running it as soon as the service is deployed. We also need to set restart_policy.condition to none to prevent Gantry from restarting automatically after a cronjob. Refer to the swarm-cronjob document for more information.
service_to_be_updated is another service managed by the swarm-cronjob and updated by Gantry. The label gantry.update.options=--replicas=0 is set on the service so that only swarm-cronjob starts it. Updating the image does not start the service.