<p>As per the <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/setup-configuration-memory.html#setup-configuration-memory" rel="nofollow noreferrer">official es docs</a>, disabling swapping is one of the best performance boosts available to Elasticsearch.</p>

<p>However, it's proving to be difficult to configure. I've spent a number of hours researching and attempting different methods to disable swapping using the official ES docker image on Kubernetes.</p>

<p>When setting <code>bootstrap.memory_lock: true</code> as an env variable, the image fails to boot up with the error: <code>Unable to lock JVM Memory: error=12, reason=Cannot allocate memory. This can result in part of the JVM being swapped out. Increase RLIMIT_MEMLOCK, soft limit: 65536, hard limit: 65536</code>. As the docs point out, this is kind of expected. I've even mounted a custom <code>/etc/security/limits.conf</code> with the settings, but that's failed.</p>

<p>What is the recommended way to disable swapping when using the official es image on k8s?</p>

<p>And, here are the relevant sections of my yaml</p>

<pre><code>apiVersion: apps/v1beta1
kind: StatefulSet
metadata:
  name: elastic-data
spec:
  serviceName: elastic-data
  replicas: 1
  template:
    spec:
      securityContext:
        runAsUser: 0
        fsGroup: 0
      containers:
      - name: elastic-data
        image: docker.elastic.co/elasticsearch/elasticsearch-oss:6.4.0
        env:
        - name: ES_JAVA_OPTS
          value: "-Xms2g -Xmx2g"
        - name: cluster.name
          value: "elastic-devs"
        - name: node.name
          valueFrom:
            fieldRef:
              fieldPath: metadata.name
        - name: discovery.zen.ping.unicast.hosts
          value: "elastic-master.default.svc.cluster.local"
        - name: node.master
          value: "false"
        - name: node.ingest
          value: "false"
        - name: node.data
          value: "true"
        - name: network.host
          value: "0.0.0.0"
        - name: path.data
          value: /usr/share/elasticsearch/data
        - name: indices.memory.index_buffer_size
          value: "512MB"
        - name: bootstrap.memory_lock
          value: "true"
        resources:
          requests:
            memory: "3Gi"
          limits:
            memory: "3Gi"
        ports:
        - containerPort: 9300
          name: transport
        - containerPort: 9200
          name: http
        volumeMounts:
        - name: data-volume
          mountPath: /usr/share/elasticsearch/data
        - name: swappiness-config
          mountPath: /etc/security/limits.conf
          subPath: limits.conf
      volumes:
      - name: data-volume
        persistentVolumeClaim:
          claimName: pvc-es
     - name: swappiness-config
       configMap:
         name: swappiness-config
         items:
          - key: limits.conf
             path: limits.conf
</code></pre>

<p>limits.conf</p>

<pre><code>elasticsearch soft memlock unlimited
elasticsearch hard memlock unlimited
elasticsearch hard nofile 65536
elasticsearch soft nofile 65536
</code></pre>

<p>I think, the ulimits in my yaml weren't being recognized, so I followed <a href="https://github.com/kubernetes/kubernetes/issues/3595" rel="nofollow noreferrer">this post</a> and created an image with a custom entrypoint that set the settings.</p>
