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DNSAutoscaler

Terakhir diperbarui:2024-02-01 10:17:07

    Overview

    Add-on Description

    DNSAutoscaler is an add-on for DNS horizontal auto scaling. It obtains the number of nodes and cores of a cluster through a Deployment and then automatically scales the number of DNS replicas according to preset scaling policies. Two scaling modes are supported: Linear mode and Ladder mode.

    Linear Mode

    Sample ConfigMap configuration is as follows:
    data:
    linear: |-
    {
    "coresPerReplica": 2,
    "nodesPerReplica": 1,
    "min": 1,
    "max": 100,
    "preventSinglePointFailure": true
    }
    Formula for calculating the number of target replicas: replicas = max(ceil(cores × 1/coresPerReplica) , ceil(nodes × 1/nodesPerReplica))
    replicas = min(replicas, max)
    replicas = max(replicas, min)

    Ladder Mode

    Sample ConfigMap configuration is as follows:
    data:
    ladder: |-
    {
    "coresToReplicas":
    [
    [ 1, 1 ],
    [ 64, 3 ],
    [ 512, 5 ],
    [ 1024, 7 ],
    [ 2048, 10 ],
    [ 4096, 15 ]
    ],
    "nodesToReplicas":
    [
    [ 1, 1 ],
    [ 2, 2 ]
    ]
    }
    Calculating the quantity of target replicas: Assume that the above configuration is applied in a cluster with 100 nodes and 400 cores, then: nodesToReplicas = 2 (100>2), coresToReplicas = 3 (64<400<512), the greater value of the two is 3, so replica = 3.

    Kubernetes objects deployed in a cluster

    Kubernetes Object Name
    Requirement
    Requested Resource
    Namespace
    tke-dns-autoscaler
    Deployment
    20 M CPU and 10 Mi memory per node
    kube-system
    dns-autoscaler
    ConfigMap
    -
    kube-system
    tke-dns-autoscale
    ServiceAccount
    -
    kube-system
    tke-dns-autoscaler
    ClusterRole
    -
    kube-system
    tke-dns-autoscaler
    ClusterRoleBinding
    -
    kube-system

    Limits

    The add-on supports only clusters with Kubernetes version 1.8 and later.
    The workload of the DNS server in the cluster should be Deployment or CoreDNS.

    Notes

    During CoreDNS horizontal scaling, some CoreDNS replicas may be unavailable for a period of time. We recommend that you optimize related configurations to maximize the DNS service availability. For more information, see Configuring Smooth Upgrade.

    Component Permission Description

    Permission Description

    The permission of this component is the minimal dependency required for the current feature to operate.

    Permission Scenarios

    Feature
    Involved Object
    Involved Operation Permission
    Monitoring changes in node resources within the cluster
    node
    list/watch
    
    Modifying the number of coredns replicas deployed by the deployment
    replicationcontrollers/scale, deployments/scale, and replicasets/scale
    get/update
    
    Retrieving parameter configurations from the configmap. In the absence of configured parameters, a configmap with default parameters will be created.
    configmap
    get/create

    Permission Definition

    kind: ClusterRole
    apiVersion: rbac.authorization.k8s.io/v1
    metadata:
    name: tke-dns-autoscaler
    rules:
    - apiGroups:
    - ""
    resources:
    - nodes
    verbs:
    - list
    - watch
    - apiGroups:
    - ""
    resources:
    - replicationcontrollers/scale
    verbs:
    - get
    - update
    - apiGroups:
    - extensions
    - apps
    resources:
    - deployments/scale
    - replicasets/scale
    verbs:
    - get
    - update
    - apiGroups:
    - ""
    resources:
    - configmaps
    verbs:
    - get
    - create

    How to Use

    1. Log in to the TKE console and select Cluster in the left sidebar.
    2. On the Cluster management page, click the ID of the target cluster to go to the cluster details page.
    3. In the left sidebar, click Add-on management to go to the Add-on list page.
    4. On the Add-on list page, click Create. On the Create add-on page, select DNSAutoscaler. The default scaling configuration of this add-on is as follows:
    data:
    ladder: |-
    {
    "coresToReplicas":
    [
    [ 1, 1 ],
    [ 128, 3 ],
    [ 512, 4 ]
    ],
    "nodesToReplicas":
    [
    [ 1, 1 ],
    [ 2, 2 ]
    ]
    }
    After the add-on is created successfully, you can modify its configuration by modifying configmap/tke-dns-autoscaler under the kube-system namespace. For more information about the configuration, see the official documentation.
    5. Click Done.
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