Elastic Container Instance:Modify the shm size of a pod by mounting an emptyDir volume to the pod

Scenario

The shared memory (shm) of pods created in Kubernetes is automatically set to 64 MiB in size and is mounted to the /dev/shm directory. The size cannot be modified.

Kubernetes does not provide a method to set the size of a shm. If you want to scale up the shm of a pod, you can mount an emptyDir volume whose storage media is memory to the /dev/shm directory of the pod.

Configuration example

1. Prepare a YAML file.

   vim emptydir-shm.yaml

   The following code provides the content of an example emprydir-shm.yaml file. In the example, the medium parameter of the emptyDir volume is set to Memory, the sizeLimit parameter is set to 256Mi, and the emptyDir volume is mounted to the /dev/shm directory. This way, the shm size of the pod is increased to 256 MiB.

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: test
     labels:
       app: test
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: nginx
     template:
       metadata:
         name: nginx-test
         labels:
           app: nginx
           alibabacloud.com/eci: "true" 
       spec:
         containers:
         - name: nginx
           image: registry.cn-shanghai.aliyuncs.com/eci_open/nginx:1.14.2
           ports:
           - containerPort: 80
           volumeMounts:
           - mountPath: /dev/shm
             name: cache-volume
         volumes:
         - emptyDir:
             medium: Memory
             sizeLimit: 256Mi
           name: cache-volume

2. Create a Deployment.

   kubectl create -f emptydir-shm.yaml

3. View the results.

   Log on to the container and run the df -h command to view the disk space. The size of the disk in the /dev/shm directory is scaled up to 256 MiB.