Kubernetes DaemonSets in KubeSphere

A DaemonSet manages groups of replicated Pods while it ensures that all (or some) nodes run a copy of a Pod. As nodes are added to the cluster, DaemonSets automatically add Pods to the new nodes as needed.

For more information, see the official documentation of Kubernetes.

Use Kubernetes DaemonSets

DaemonSets are very helpful in cases where you want to deploy ongoing background tasks that run on all or certain nodes without any user intervention. For example:

  • Run a log collection daemon on every node, such as Fluentd or Logstash.
  • Run a node monitoring daemon on every node, such as Prometheus Node Exporter, collectd, and AppDynamics Agent.
  • Run a cluster storage daemon and system program on every node, such as Glusterd, Ceph, kube-dns, and kube-proxy.

Prerequisites

You need to create a workspace, a project and a user (project-regular). The user must be invited to the project with the role of operator. For more information, see Create Workspaces, Projects, Users and Roles.

Create a DaemonSet

Step 1: Open the dashboard

Log in to the console as project-regular. Go to Application Workloads of a project, select Workloads, and click Create under the tab DaemonSets.

Step 2: Enter basic information

Specify a name for the DaemonSet (for example, demo-daemonset), select a project, and click Next.

Step 3: Set a Pod

  1. Click Add Container.

  2. Enter an image name from public Docker Hub or from a private repository you specified. For example, enter fluentd in the search box and press Enter.

    Note

    • Remember to press Enter on your keyboard after you enter an image name in the search box.
    • If you want to use your private image repository, you should create an Image Registry Secret first in Secrets under Configuration.

  3. Set requests and limits for CPU and memory resources based on your needs. For more information, see Resource Request and Resource Limit in Container Image Settings.

  4. Click Use Default Ports for Port Settings or you can customize Protocol, Name and Container Port.

  5. Select a policy for image pulling from the drop-down menu. For more information, see Image Pull Policy in Container Image Settings.

  6. For other settings (Health Check, Start Command, Environment Variables, Container Security Context and Synchronize Host Timezone), you can configure them on the dashboard as well. For more information, see detailed explanations of these properties in Pod Settings. When you finish, click √ in the lower-right corner to continue.

  7. Select an update strategy from the drop-down menu. It is recommended you choose Rolling Update. For more information, see Update Strategy.

  8. Select a Pod scheduling rule. For more information, see Pod Scheduling Rules.

  9. Click Next to continue when you finish setting the container image.

Step 4: Mount volumes

You can add a volume directly or mount a ConfigMap or Secret. Alternatively, click Next directly to skip this step. For more information about volumes, visit Volumes.

Note

DaemonSets can’t use a volume template, which is used by StatefulSets.

Step 5: Configure advanced settings

You can add metadata in this section. When you finish, click Create to complete the whole process of creating a DaemonSet.

  • Add Metadata

    Additional metadata settings for resources such as Labels and Annotations.

Check Kubernetes DaemonSet Details

Details page

  1. After a DaemonSet is created, it will be displayed in the list. You can click icon on the right and select the options from the menu to modify a DaemonSet.

    • Edit Information: View and edit the basic information.
    • Edit YAML: View, upload, download, or update the YAML file.
    • Re-create: Re-create the DaemonSet.
    • Delete: Delete the DaemonSet.

  2. Click the name of the DaemonSet and you can go to its details page.

  3. Click More to display what operations about this DaemonSet you can do.

    • Roll Back: Select the revision to roll back.
    • Edit Settings: Configure update strategies, containers and volumes.
    • Edit YAML: View, upload, download, or update the YAML file.
    • Re-create: Re-create this DaemonSet.
    • Delete: Delete the DaemonSet, and return to the DaemonSet list page.

  4. Click the Resource Status tab to view the port and Pod information of a DaemonSet.

    • Replica Status: You cannot change the number of Pod replicas for a DaemonSet.

    • Pods

      • The Pod list provides detailed information of the Pod (status, node, Pod IP and resource usage).
      • You can view the container information by clicking a Pod item.
      • Click the container log icon to view output logs of the container.
      • You can view the Pod details page by clicking the Pod name.

Revision records

After the resource template of workload is changed, a new log will be generated and Pods will be rescheduled for a version update. The latest 10 versions will be saved by default. You can implement a redeployment based on the change log.

Metadata

Click the Metadata tab to view the labels and annotations of the DaemonSet.

Monitoring

  1. Click the Monitoring tab to view the CPU usage, memory usage, outbound traffic, and inbound traffic of the DaemonSet.

  2. Click the drop-down menu in the upper-right corner to customize the time range and sampling interval.

  3. Click icon/icon in the upper-right corner to start/stop automatic data refreshing.

  4. Click icon in the upper-right corner to manually refresh the data.

Environment variables

Click the Environment Variables tab to view the environment variables of the DaemonSet.

Events

Click the Events tab to view the events of the DaemonSet.

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