Help Center/ Ubiquitous Cloud Native Service/ User Guide/ Cluster Federation/ Workloads/ Container Settings/ Configuring Scheduling and Differentiation
Updated on 2024-09-19 GMT+08:00
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Configuring Scheduling and Differentiation

Scheduling Policies

Currently, there are two scheduling policies: cluster weights and automatic balancing.

Configuring a Scheduling Policy on the Console

  1. Log in to the UCS console.
  2. When creating a workload, click Next: Scheduling and Differentiation.
  3. Add a scheduling policy.

    Table 1 Scheduling policies

    Policy

    Description

    Cluster weights

    You need to select clusters and configure their weights. Pods are allocated to clusters based on the cluster weights.

    Auto balancing

    The system automatically selects clusters to allocate pods based on the number of remaining pods. No extra configuration is required.

Calculation Method Based on Cluster Weights

Calculation Method

After you set the weight of each cluster, the number of pods allocated to each cluster is calculated as follows:

  1. Formula for calculating the number of pods allocated to each cluster by cluster weight (The calculation result is rounded down.)

    Number of pods allocated to each cluster = (Total number of pods × Weight of a cluster)/Total weight of clusters

  2. Formula for calculating the number of remaining pods

    Number of remaining pods = Total number of pods - Total number of pods allocated to each cluster

  3. If there are any pods remaining, they will continue to be allocated by cluster weight in ascending order (one pod allocated at a time). If any clusters have the same weight, a cluster will be selected at random.

Example

There are seven pods that are assigned to three clusters named member1, member2, and member3. The clusters have weights of 2, 1, and 1, respectively.

  1. The number of pods allocated to each cluster is calculated as follows:

    Number of pods allocated to member1 = 7 × 2/4 (rounded down to 3)

    Number of pods allocated to member2 = 7 × 1/4 (rounded down to 1)

    Number of pods allocated to member3 = 7 × 1/4 (rounded down to 1)

    In this initial allocation, three pods are allocated to member1, one pod to member2, and one pod to member3.

  2. The number of remaining pods is calculated as follows:

    Number of remaining pods = 7 - 3 - 1 - 1 = 2

  3. The remaining pods are allocated by cluster weight in ascending order.

    One pod is first allocated to member1 and the remaining pod to member2 or member3 at random.

Tolerance Policies

A tolerance policy allows the scheduler to schedule pods to clusters with corresponding taints. This policy must be used together with cluster taints.

Using the Default Tolerance Policy

When you create a workload, UCS configures a default tolerance policy for your workload. The default tolerance policy adds taints listed in Table 2 to a faulty cluster. If the tolerance duration is exceeded, all pods in the cluster will be automatically evicted.

After all pods in the faulty cluster are evicted, UCS does not migrate the pods back to the cluster based on the original scheduling policy after the cluster recovers. If you want to continue with the original scheduling policy configuration, you can reschedule the workload.

Table 2 Taints for faulty clusters

Taint Key

Tolerance Policy

cluster.karmada.io/not-ready

When the cluster is not ready, this taint is automatically added. If the tolerance duration is exceeded, all pods in the cluster will be automatically evicted.

cluster.karmada.io/unreachable

When the cluster is unavailable, this taint is automatically added. If the tolerance duration is exceeded, all pods in the cluster will be automatically evicted.

Configuring a Tolerance Policy on the Console

  1. Log in to the UCS console.
  2. When creating a workload, click Next: Scheduling and Differentiation.
  3. Add a tolerance policy.

    Parameter

    Description

    Taint Key

    Taint key of the cluster.

    Operator
    • Equal: matches the nodes with the specified taint key (mandatory) and value. If the taint value is left blank, all taints with the key the same as the specified taint key will be matched.
    • Exists: matches the nodes with the specified taint key. In this case, the taint value cannot be specified. If the taint key is left blank, all taints will be tolerated.

    Taint Value
    • If the value of Operator is Exists, the value attribute can be omitted.
    • If the value of Operator is Equal, the relationship between the key and value is Equal.
    • If Operator is not specified, the default value is Equal.

    Taint Policy
    • All: All taint policies are matched.
    • NoSchedule: Only the NoSchedule taint is matched.
    • NoExecute: Only the NoExecute taint is matched.

    Toleration Time Window

    tolerationSeconds, which is configurable only when Taint Policy is set to NoExecute.

    Within the tolerance time window, pods still run on the node with taints. After the time expires, the pods will be evicted. If the tolerance time window is not configured, the pods will never be evicted.

Parent topic: Container Settings