Creating a StatefulSet

Scenario

Notes and Constraints

• When you delete or scale a StatefulSet, the system does not delete the storage volumes associated with the StatefulSet to ensure data security.
• When you delete a StatefulSet, reduce the number of replicas to 0 before deleting the StatefulSet so that pods in the StatefulSet can be stopped in order.
• When you create a StatefulSet, a headless Service is required for pod access. For details, see Headless Services.
• When a node is unavailable, pods become Unready. In this case, manually delete the pods of the StatefulSet so that the pods can be migrated to a normal node.

Prerequisites

• Before creating a workload, you must have an available cluster. For details on how to create a cluster, see Buying a CCE Standard/Turbo Cluster.
• To enable public access to a workload, ensure that an EIP or load balancer has been bound to at least one node in the cluster.
  Note

  If a pod has multiple containers, ensure that the ports used by the containers do not conflict with each other. Otherwise, creating the StatefulSet will fail.

Using the CCE Console

1. Log in to the CCE console.
2. Click the cluster name to go to the cluster console, choose Workloads in the navigation pane, and click the Create Workload in the upper right corner.
3. Set basic information about the workload.

   Basic Info

   • Workload Type: Select StatefulSet. For details about workload types, see Overview.
   • Workload Name: Enter the name of the workload. Enter 1 to 63 characters starting with a lowercase letter and ending with a lowercase letter or digit. Only lowercase letters, digits, and hyphens (-) are allowed.
   • Namespace: Select the namespace of the workload. The default value is default. You can also click Create Namespace to create one. For details, see Creating a Namespace.
   • Pods: Enter the number of pods of the workload.
   • Container Runtime: A CCE standard cluster uses a common runtime by default, whereas a CCE Turbo cluster supports both common and secure runtimes. For details about the differences, see Secure Runtime and Common Runtime.
   • Time Zone Synchronization: Specify whether to enable time zone synchronization. After time zone synchronization is enabled, the container and node use the same time zone. The time zone synchronization function depends on the local disk mounted to the container. Do not modify or delete the time zone. For details, see Configuring Time Zone Synchronization.

   Container Settings

   • Container Information

     Multiple containers can be configured in a pod. You can click Add Container on the right to configure multiple containers for the pod.

     • Basic Info: Configure basic information about the container.

       Parameter	Description
       Container Name	Name the container.
       Pull Policy	Image update or pull policy. If you select Always, the image is pulled from the image repository each time. If you do not select Always, the existing image of the node is preferentially used. If the image does not exist, the image is pulled from the image repository.
       Image Name	Click Select Image and select the image used by the container. To use a third-party image, directly enter image path. Ensure that the image access credential can be used to access the image repository. For details, see Using Third-Party Images.
       Image Tag	Select the image tag to be deployed.
       CPU Quota	Request: minimum number of CPU cores required by a container. The default value is 0.25 cores. Limit: maximum number of CPU cores that can be used by a container. This prevents containers from using excessive resources. If Request and Limit are not specified, the quota is not limited. For more information and suggestions about Request and Limit, see Configuring Container Specifications.
       Memory Quota	Request: minimum amount of memory required by a container. The default value is 512 MiB. Limit: maximum amount of memory available for a container. When memory usage exceeds the specified memory limit, the container will be terminated. If Request and Limit are not specified, the quota is not limited. For more information and suggestions about Request and Limit, see Configuring Container Specifications.
       (Optional) GPU Quota	Configurable only when the cluster contains GPU nodes and the CCE AI Suite (NVIDIA GPU) add-on has been installed. Do not use: No GPU will be used. GPU card: The GPU is dedicated for the container. GPU Virtualization: percentage of GPU resources used by the container. For example, if this parameter is set to 10%, the container will use 10% of GPU resources. For details about how to use GPUs in the cluster, see Default GPU Scheduling in Kubernetes.
       (Optional) Privileged Container	Programs in a privileged container have certain privileges. If Privileged Container is enabled, the container is assigned privileges. For example, privileged containers can manipulate network devices on the host machine and modify kernel parameters.
       (Optional) Init Container	Whether to use the container as an init container. An init container does not support health check. An init container is a special container that runs before other app containers in a pod are started. Each pod can contain multiple containers. In addition, a pod can contain one or more init containers. Application containers in a pod are started and run only after the running of all init containers completes. For details, see Init Containers.
       (Optional) Run Option	Add run options for the container. For details, see Pod. CCE supports the following run options: stdin: allows containers to receive input from external sources, such as terminals or other input streams. tty: allocates a pseudo terminal to containers, allowing you to send commands to them as if you were using a local terminal. In most cases, tty is enabled along with stdin, indicating that the terminal (tty) is associated with the standard input (stdin) of the container. This allows for interactive operations, similar to the kubectl exec -i -t command. The difference is that this parameter has been configured when the pod is launched.

     • (Optional) Lifecycle: Configure operations to be performed in a specific phase of the container lifecycle, such as Startup Command, Post-Start, and Pre-Stop. For details, see Configuring Container Lifecycle Parameters.
     • (Optional) Health Check: Set the liveness probe, ready probe, and startup probe as required. For details, see Configuring Container Health Check.
     • (Optional) Environment Variables: Configure variables for the container running environment using key-value pairs. These variables transfer external information to containers running in pods and can be flexibly modified after application deployment. For details, see Configuring Environment Variables.
     • (Optional) Data Storage: Mount local storage or cloud storage to the container. The application scenarios and mounting modes vary with the storage type. For details, see Storage.
       Note

       • StatefulSets support dynamic attachment of EVS disks. For details, see Dynamically Mounting an EVS Disk to a StatefulSet or Dynamically Mounting a Local PV to a StatefulSet.

         Dynamic mounting is achieved by using the volumeClaimTemplates field and depends on the dynamic creation capability of StorageClass. A StatefulSet associates each pod with a PVC using the volumeClaimTemplates field, and the PVC is bound to the corresponding PV. Therefore, after the pod is rescheduled, the original data can still be mounted based on the PVC name.

       • After a workload is created, the storage that is dynamically mounted cannot be updated.
     • (Optional) Security Context: Assign container permissions to protect the system and other containers from being affected. Enter the user ID to assign container permissions and prevent systems and other containers from being affected.
     • (Optional) Logging: Report standard container output logs to AOM by default, without requiring manual settings. You can manually configure the log collection path. For details, see Collecting Container Logs Using ICAgent.

       To disable the standard output of the current workload, add the annotation kubernetes.AOM.log.stdout: [] in Labels and Annotations. For details about how to use this annotation, see Table 1.

   • Image Access Credential: Select the credential used for accessing the image repository. The default value is default-secret. You can use default-secret to access images in SWR Shared Edition. For details about default-secret, see default-secret.
   • (Optional) GPU: All is selected by default. The workload instance will be scheduled to the node of the specified GPU type.

   Headless Service Parameters

   A headless Service is used to solve the problem of mutual access between pods in a StatefulSet. The headless Service provides a fixed access domain name for each pod. For details, see Headless Services.

   (Optional) Service Settings

   A Service provides external access for pods. With a static IP address, a Service forwards access traffic to pods and automatically balances load for these pods.

   You can also create a Service after creating a workload. For details about Services of different types, see Overview.

   (Optional) Advanced Settings

   • Upgrade: Specify the upgrade mode and parameters of the workload. Rolling upgrade and Replace upgrade are available. For details, see Configuring Workload Upgrade Policies.
   • Pod Management Policies

     For some distributed systems, the StatefulSet sequence is unnecessary and/or should not occur. These systems require only uniqueness and identifiers.

     • OrderedReady: The StatefulSet will deploy, delete, or scale pods in order and one by one. (The StatefulSet continues only after the previous pod is ready or deleted.) This is the default policy.
     • Parallel: The StatefulSet will create pods in parallel to match the desired scale without waiting, and will delete all pods at once.
   • Scheduling: Configure affinity and anti-affinity policies for flexible workload scheduling. Load affinity and node affinity are provided.
     • Load Affinity: Common load affinity policies are offered for quick load affinity deployment.
       • Not configured: No load affinity policy is configured.
       • Multi-AZ deployment preferred: Workload pods are preferentially scheduled to nodes in different AZs through pod anti-affinity.
       • Forcible multi-AZ deployment: Workload pods are forcibly scheduled to nodes in different AZs through pod anti-affinity (podAntiAffinity). If there are fewer AZs than pods, the extra pods will fail to run.
       • Customize affinity: Affinity and anti-affinity policies can be customized. For details, see Configuring Workload Affinity or Anti-affinity Scheduling (podAffinity or podAntiAffinity).
     • Node Affinity: Common node affinity policies are offered for quick load affinity deployment.
       • Not configured: No node affinity policy is configured.
       • Specify node: Workload pods can be deployed on specified nodes through node affinity (nodeAffinity). If no node is specified, the pods will be randomly scheduled based on the default scheduling policy of the cluster.
       • Specify node pool: Workload pods can be deployed in a specified node pool through node affinity (nodeAffinity). If no node pool is specified, the pods will be randomly scheduled based on the default scheduling policy of the cluster.
       • Customize affinity: Affinity and anti-affinity policies can be customized. For details, see Configuring Node Affinity Scheduling (nodeAffinity).
   • Toleration: Using both taints and tolerations allows (not forcibly) the pod to be scheduled to a node with the matching taints, and controls the pod eviction policies after the node where the pod is located is tainted. For details, see Configuring Tolerance Policies.
   • Labels and Annotations: Add labels or annotations for pods using key-value pairs. After entering the key and value, click Confirm. For details about how to use and configure labels and annotations, see Configuring Labels and Annotations.
   • DNS: Configure a separate DNS policy for the workload. For details, see DNS Configuration.
   • Network Configuration
     • Pod ingress/egress bandwidth limitation: You can set ingress/egress bandwidth limitation for pods. For details, see Configuring QoS for a Pod.
     • Whether to enable a specified container network configuration: available only for clusters that support this function. After you enable a specified container network configuration, the workload will be created using the container subnet and security group in the configuration. For details, see Binding a Subnet and Security Group to a Namespace or Workload Using a Container Network Configuration.
     • Specify the container network configuration name: Only the custom container network configuration whose associated resource type is workload can be selected.
     • IPv6 shared bandwidth: available only for clusters that support this function. After this function is enabled, you can configure a shared bandwidth for a pod with IPv6 dual-stack ENIs. For details, see Configuring Shared Bandwidth for a Pod with IPv6 Dual-Stack ENIs.

4. Click Create Workload in the lower right corner. After a period of time, the workload enters the Running state.

Using kubectl

1. Use kubectl to access the cluster. For details, see Accessing a Cluster Using kubectl.
2. Create and edit the nginx-statefulset.yaml file.

   nginx-statefulset.yaml is an example file name, and you can change it as required.

   vi nginx-statefulset.yaml
   
   

   The following provides an example of the file contents. For more information on StatefulSet, see the Kubernetes documentation.

   apiVersion: apps/v1
   kind: StatefulSet
   metadata:
     name: nginx
   spec:
     selector:
       matchLabels:
         app: nginx
     template:
       metadata:
         labels:
           app: nginx
       spec:
         containers:
           - name: container-1
             image: nginx:latest
             imagePullPolicy: IfNotPresent
             resources:
               requests:
                 cpu: 250m
                 memory: 512Mi
               limits:
                 cpu: 250m
                 memory: 512Mi
             volumeMounts:
               - name: test
                 readOnly: false
                 mountPath: /usr/share/nginx/html
                 subPath: ''
         imagePullSecrets:
           - name: default-secret
         dnsPolicy: ClusterFirst
         volumes: []
     serviceName: nginx-svc
     replicas: 2
     volumeClaimTemplates:  # Dynamically mounts the EVS volume to the workload.
       - apiVersion: v1
         kind: PersistentVolumeClaim
         metadata:
           name: test
           namespace: default
           annotations:
             everest.io/disk-volume-type: SAS  # SAS EVS volume type.
           labels:
             failure-domain.beta.kubernetes.io/region: ru-moscow-1  # region where the EVS volume is created.
             failure-domain.beta.kubernetes.io/zone:    # AZ where the EVS volume is created. It must be the same as the AZ of the node.
         spec:
           accessModes:
             - ReadWriteOnce  # The value must be ReadWriteOnce for the EVS volume.
           resources:
             requests:
               storage: 10Gi
           storageClassName: csi-disk # StorageClass name. The value is csi-disk for the EVS volume.
     updateStrategy:
       type: RollingUpdate
   
   

   Create and edit the nginx-headless.yaml file.

   vi nginx-headless.yaml
   
   

   The content is as follows:

   apiVersion: v1
   kind: Service
   metadata:
     name: nginx-svc
     namespace: default
     labels:
       app: nginx
   spec:
     selector:
       app: nginx
       version: v1
     clusterIP: None
     ports:
       - name: nginx
         targetPort: 80
         nodePort: 0
         port: 80
         protocol: TCP
     type: ClusterIP
   
   

3. Create the workload.

   kubectl create -f nginx-statefulset.yaml
   
   

   If the following information is displayed, the StatefulSet has been successfully created.

   statefulset.apps/nginx created
   
   

   Create a headless Service.

   kubectl create -f nginx-headless.yaml
   
   

   If the following information is displayed, the headless service has been successfully created.

   service/nginx-svc created
   
   

4. If the workload will be accessed through a ClusterIP or NodePort Service, configure the access mode. For details, see Network.