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Creating a DaemonSet

Scenario

CCE provides deployment and management capabilities for multiple types of containers and supports features of container workloads, including creation, configuration, monitoring, scaling, upgrade, uninstall, service discovery, and load balancing.

DaemonSet ensures that only one pod runs on all or some nodes. When a node is added to a cluster, a new pod is also added for the node. When a node is removed from a cluster, the pod is also reclaimed. If a DaemonSet is deleted, all pods created by it will be deleted.

The typical application scenarios of a DaemonSet are as follows:

  • Run the cluster storage daemon, such as glusterd or Ceph, on each node.
  • Run the log collection daemon, such as Fluentd or Logstash, on each node.
  • Run the monitoring daemon, such as Prometheus Node Exporter, collectd, Datadog agent, New Relic agent, or Ganglia (gmond), on each node.

You can deploy a DaemonSet for each type of daemons on all nodes, or deploy multiple DaemonSets for the same type of daemons. In the second case, DaemonSets have different flags and different requirements on memory and CPU for different hardware types.

Prerequisites

You must have one cluster available before creating a DaemonSet. For details on how to create a cluster, see Buying a CCE Cluster.

Creating from Image

  1. Log in to the CCE console.
  2. Click the cluster name to access its details page, choose Workloads on the left, and click the Create from Image tab in the upper right corner.
  3. Set basic information about the workload.

    Basic Info
    • Workload Type: Select DaemonSet. For details about workload types, see Overview.
    • Workload Name: Enter the name of the workload.
    • 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.
    • Container Runtime: A CCE cluster uses runC by default, whereas a CCE Turbo cluster supports both runC and Kata. For details about the differences between runC and Kata, see Secure Containers and Common Containers.
    • 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.
    • 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. For details about default-secret, see default-secret.

    Service Settings

    A Service is used for pod access. With a fixed IP address, a Service forwards access traffic to pods and performs load balancing for these pods.

    You can also create a Service after creating a workload. For details about the Service, see Overview.

    Advanced Settings

  4. Click Create Workload in the lower right corner.

Using kubectl

The following procedure uses Nginx as an example to describe how to create a workload using kubectl.

  1. Use kubectl to connect to the cluster. For details, see Connecting to a Cluster Using kubectl.
  2. Create and edit the nginx-daemonset.yaml file. nginx-daemonset.yaml is an example file name, and you can change it as required.

    vi nginx-daemonset.yaml

    The content of the description file is as follows: The following provides an example. For more information on DaemonSets, see Kubernetes documents.

    apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: nginx-daemonset
  labels:
    app: nginx-daemonset
spec:
  selector:
    matchLabels:
      app: nginx-daemonset
  template:
    metadata:
      labels:
        app: nginx-daemonset
    spec:
      nodeSelector:                 # Node selection. A pod is created on a node only when the node meets daemon=need.
        daemon: need
      containers:
      - name: nginx-daemonset
        image: nginx:alpine
        resources:
          limits:
            cpu: 250m
            memory: 512Mi
          requests:
            cpu: 250m
            memory: 512Mi
      imagePullSecrets:
      - name: default-secret

    The replicas parameter used in defining a Deployment or StatefulSet does not exist in the above configuration for a DaemonSet, because each node has only one replica. It is fixed.

    The nodeSelector in the preceding pod template specifies that a pod is created only on the nodes that meet daemon=need, as shown in the following figure. If you want to create a pod on each node, delete the label.

  3. Create a DaemonSet.

    kubectl create -f nginx-daemonset.yaml

    If the following information is displayed, the DaemonSet is being created.

    daemonset.apps/nginx-daemonset created

  4. Query the DaemonSet status.

    kubectl get ds

    $ kubectl get ds
NAME              DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR   AGE
nginx-daemonset   1         1         0       1            0           daemon=need     116s

  5. If the workload will be accessed through a ClusterIP or NodePort Service, set the corresponding workload access type. For details, see Networking.
Parent topic: Workloads