memcached-persistent.yaml

apiVersion: v1
kind: Service
metadata:
  name: pmem-memcached
  namespace: default
spec:
  ports:
  - name: db
    port: 11211
    protocol: TCP
    targetPort: db
  selector:
    app.kubernetes.io/kind: memcached
    app.kubernetes.io/name: pmem-memcached
  type: ClusterIP
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: pmem-memcached
  namespace: default
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/kind: memcached
      app.kubernetes.io/name: pmem-memcached
  serviceName: pmem-memcached
  template:
    metadata:
      labels:
        app.kubernetes.io/kind: memcached
        app.kubernetes.io/name: pmem-memcached
    spec:
      initContainers:
      - name: data-volume-init
        # This first creates a file that is as large as root can make it (larger
        # than a normal user because of reserved blocks). Size is rounded down to
        # MiB because that is what memcached expects and 50 MiB are substracted
        # for filesystem overhead and the memcached state files.
        #
        # Then it changes the ownership of the data volume so that the memcached user
        # can read and write files there. The exact UID varies between
        # memcached image versions (therefore we cannot use Kubernetes to change
        # the ownership for us as that relies on a numeric value), but the "memcache"
        # name is the same, so by running in the same image as memcached we can set
        # the owner by name.
        command:
        - sh
        - -c
        - |
          fallocate --length=$(( $(stat --file-system --format='%b * %s / 1024 / 1024 - 50' /data) ))MiB /data/memcached-memory-file &&
          chown -R memcache /data
        image: memcached:1.5.22
        securityContext:
          privileged: true
          runAsUser: 0
        volumeMounts:
        - mountPath: /data
          name: memcached-data-volume
      containers:
      - name: memcached
        image: memcached:1.5.22
        command:
        - sh
        - -c
        - |
          set -x
          memcached --memory-limit=$(( $(stat --format='%s / 1024 / 1024' /data/memcached-memory-file) )) --memory-file=/data/memcached-memory-file $(MEMCACHED_ARGS) &
          pid=$$!
          trap 'kill -USR1 $$pid; wait $$pid' TERM
          wait $$pid
        ports:
        - containerPort: 11211
          name: db
          protocol: TCP
        volumeMounts:
        - mountPath: /data
          name: memcached-data-volume
        env:
        - name: MEMCACHED_ARGS
          value:
      terminationGracePeriodSeconds: 30
  volumeClaimTemplates:
    - metadata:
        name: memcached-data-volume
      spec:
        accessModes: [ "ReadWriteOnce" ]
        storageClassName: pmem-csi-sc-ext4
        resources:
          requests:
            storage: 200Mi