We have Celery Beat set up using the following deployment.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: celery-beat
  labels:
    deployment: celery-beat
spec:
  replicas: 1
  minReadySeconds: 120
  selector:
    matchLabels:
      app: celery-beat
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 0 # Would rather have downtime than an additional instance in service?
      maxUnavailable: 1
  template:
    metadata:
      labels:
        app: celery-beat
    spec:
      containers:
        - name: celery-beat
          image: image_url
          command: ["/var/app/scripts/kube_worker_beat_start.sh"]
          imagePullPolicy: Always
          ports:
            - containerPort: 8000
              name: http-server
          livenessProbe: #From https://github.com/celery/celery/issues/4079#issuecomment-437415370
            exec:
              command:
                - /bin/sh
                - -c
                - celery -A app_name status | grep ".*OK"
            initialDelaySeconds: 3600 
            periodSeconds: 3600
          readinessProbe:
            exec:
              command:
                - /bin/sh
                - -c
                - celery -A app_name status | grep ".*OK"
            initialDelaySeconds: 60
            periodSeconds: 30 
          resources:
            limits:
              cpu: "0.5" #500mcores - only really required on install
            requests:
              cpu: "30m"

I have found the RollingUpdate settings tricky because with Celery Beat you really don't want two instances, otherwise you might get duplicate tasks being completed. This is super important for us to avoid since we're using it to send out push notifications.

With the current settings, when a deployment rolls out there is 3-5mins of downtime, because the existing instance is terminated immediately and we have to wait for the new one to set itself up.

Is there a better way of configuring this reduce the downtime whilst ensuring a maximum of one service is ever in service?