on_write.ex

def handle_call({:add, event}, _from, worker) do
  logEntry = %LogEntry{
    origin: worker.name,
    time: worker.clock,
    event: event
  }
  newWorkerState = %{ worker |
    clock: worker.clock + 1,
    eventLog: [logEntry | worker.eventLog]
  }
  PubSub.broadcast(@log_replication_topic, {:replication_log, logEntry})
  {:reply, :ok, newWorkerState }
end