I am using Elastic Search(v7.6.1) on a Kubernetes(v1.19) cluster.

The docs suggests to disable swapping:

https://www.elastic.co/guide/en/elasticsearch/reference/current/setup-configuration-memory.html

My yaml:

apiVersion: elasticsearch.k8s.elastic.co/v1
kind: Elasticsearch
metadata:
  name: elastic-cluster-1
spec:
  version: 7.6.1
  image: docker.elastic.co/elasticsearch/elasticsearch:7.6.1
  nodeSets:
  - name: default
    count: 3
    config:
      node.master: true
      node.data: true
      node.ingest: true
    podTemplate:
      metadata:
        labels:
          # additional labels for pods
          type: elastic-master-node
      spec:
        nodeSelector:
          node-pool: <NODE_POOL>
        initContainers:
        # Increase linux map count to allow elastic to store large memory maps
        - name: sysctl
          securityContext:
            privileged: true
          command: ['sh', '-c', 'sysctl -w vm.max_map_count=262144']
        containers:
        - name: elasticsearch
          # specify resource limits and requests
          resources:
            limits:
              memory: 11.2Gi
            requests:
              cpu: 3200m
          env:
          - name: ES_JAVA_OPTS
            value: "-Xms6g -Xmx6g"
    # Request persistent data storage for pods
    volumeClaimTemplates:
    - metadata:
        name: elasticsearch-data
      spec:
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 50Gi
        storageClassName: ssd
  - name: data
    count: 2
    config:
      node.master: false
      node.data: true
      node.ingest: true
    podTemplate:
      metadata:
        labels:
          # additional labels for pods
          type: elastic-data-node
      spec:
        nodeSelector:
          node-pool: <NODE_POOL>
        initContainers:
        # Increase linux map count to allow elastic to store large memory maps
        - name: sysctl
          securityContext:
            privileged: true
          command: ['sh', '-c', 'sysctl -w vm.max_map_count=262144']
        containers:
        - name: elasticsearch
          # specify resource limits and requests
          resources:
            limits:
              memory: 11.2Gi
            requests:
              cpu: 3200m
          env:
          - name: ES_JAVA_OPTS
            value: "-Xms6g -Xmx6g"
    # Request persistent data storage for pods
    volumeClaimTemplates:
    - metadata:
        name: elasticsearch-data
      spec:
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 50Gi
        storageClassName: ssd
  # Google cloud storage credentials
  secureSettings:
  - secretName: "gcs-credentials"
  http:
    service:
      spec:
        # expose this cluster Service with a LoadBalancer
        type: LoadBalancer
    tls:
      certificate:
        secretName: elasticsearch-certificate

It's not clear to me how to change this yaml in order to disable swapping correctly. Changing each manually is not an option because in every restart the configuration will be lost.

How can I do this?

CodePudding user response：

First of all k8s cluster by default will have swap disabled, this is actually a mandatory requirement. For most cases; especially cloud managed cluster which follows the requirement, you do not need to worry about swapping issue. Even for 1.22, enabling swap is only an alpha feature.

If for whatever reason you need to deal with this, you can consider setting bootstrap.memory_lock to true.

...
containers:
- name: elasticsearch
  env:
  - name: bootstrap.memory_lock
    value: "true"
...

CodePudding user response：

Up until recently, Kubernetes had no control over swapping.

As of 1.22, there's a new alpha feature to do this. The CRI spec does allow for swap allocations. I didn't find anything new in that regard, in the Pod specification: as far as I understand, currently, you could either allow your containers to use as much swap as they can (UnlimitedSwap), or limit swap memory usage to whatever memory limit you set on your container (LimitedSwap).

Since you're running 1.19, this shouldn't concern you right now. A good practice while deploying your cluster would have been to make sure there is no swap at all on your nodes, or set swapiness to 0 or 1. Checking Kubespray playbooks, we can see they would still unconditionally disable swap.

You can connect your nodes (ssh), make sure there's no swap -- or disable it otherwise. There's nothing you can do in that ElasticSearch object directly.