We have elixir application deployed on two servers. The application has been configured with some quantum jobs which execute from both servers at the same time. We want to limit execution of the quantum jobs to a single server. As per documentation, we could see the following options,

1. Add global?: true to the job configuration
2. run_strategy: {Quantum.RunStrategy.Random, :cluster}

We tried option (1), it didnt work. The job still executed from both servers. Do both (1) and (2) need to be set at the same time in a job? or there something else missing in the configuration

config :titan, Titan.Scheduler,
  timeout: 20_000,
  global?: true,
  jobs: [
    job_schedule: [
      schedule: "20 6 * * *",
      task: {Titan.ContentSchedule, :schedule_updates, []}
    ],
]

How does this clustering work? Even without giving the list of nodes, how do the two servers communicate among themselves to co-ordinate the job execution?