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2.12 Configuring Scheduler Profiles

Kubernetes Scheduler Profiles let you run multiple logical schedulers inside a single scheduler binary. Each profile behaves like an independent scheduler but shares the same process — reducing operational overhead and avoiding race conditions between multiple scheduler instances.

Info

Scheduler Profiles were introduced in Kubernetes v1.18+.

Why Scheduler Profiles

Before Scheduler Profiles, running multiple schedulers required:

  • Separate scheduler binaries
  • Separate configuration files
  • Separate running processes

This led to:

  • Higher maintenance overhead
  • More resource usage
  • Possible race conditions between schedulers

Note

Scheduler Profiles allow multiple scheduler behaviors inside one scheduler process instead of running multiple scheduler services.

What Is a Scheduler Profile

A Scheduler Profile is a configuration block inside the scheduler configuration file that defines:

  • A unique scheduler name
  • Plugin configuration
  • Extension point behavior

Each profile:

  • Acts like a separate logical scheduler
  • Uses the same kube-scheduler binary
  • Can behave differently through plugin settings

How Pods Choose a Scheduler Profile

Pods select which scheduler profile to use with the schedulerName field.

apiVersion: v1
kind: Pod
metadata:
  name: example-pod
spec:
  schedulerName: my-scheduler-2
  containers:
    - name: nginx
      image: nginx

If schedulerName is not specified, the default profile (default-scheduler) is used.

Scheduler Profiles — Concept Diagram

                    ┌──────────────────────────────┐
                    │        kube-scheduler        │
                    │        (single binary)       │
                    └──────────────┬───────────────┘
                                   │
        ┌──────────────────────────┼──────────────────────────┐
        │                          │                          │
        ▼                          ▼                          ▼

┌──────────────────┐     ┌──────────────────┐     ┌──────────────────┐
│ Profile A        │     │ Profile B        │     │ Profile C        │
│ schedulerName:   │     │ schedulerName:   │     │ schedulerName:   │
│ default-scheduler│     │ my-scheduler-2   │     │ my-scheduler-3   │
│                  │     │                  │     │                  │
│ Default plugins  │     │ Custom plugins   │     │ Scoring disabled │
└──────────────────┘     └──────────────────┘     └──────────────────┘

        │                          │                          │
        ▼                          ▼                          ▼

 Pods without              Pods with                   Pods with
 schedulerName      schedulerName=my-scheduler-2  schedulerName=my-scheduler-3

Configuring Multiple Profiles

Multiple profiles are defined under the profiles section in the scheduler configuration.

Example Configuration

apiVersion: kubescheduler.config.k8s.io/v1
kind: KubeSchedulerConfiguration

profiles:

  - schedulerName: my-scheduler-2
    plugins:
      score:
        disabled:
          - name: TaintToleration
        enabled:
          - name: MyCustomPluginA
          - name: MyCustomPluginB

  - schedulerName: my-scheduler-3
    plugins:
      preScore:
        disabled:
          - name: "*"
      score:
        disabled:
          - name: "*"

  - schedulerName: my-scheduler-4

Tip

Each profile can enable or disable plugins independently to change scheduling behavior.

Scheduler Extension Points

Scheduler plugins run at different extension points during the scheduling cycle.

Scheduling Flow Diagram

Pod Enters Queue
      │
      ▼
┌──────────────┐
│ Queue Sort   │  → Example: PrioritySort
└──────┬───────┘
       ▼
┌──────────────┐
│ Filtering    │  → NodeResourcesFit, NodeAffinity, TaintToleration
└──────┬───────┘
       ▼
┌──────────────┐
│ Scoring      │  → ImageLocality, NodeResourcesFit
└──────┬───────┘
       ▼
┌──────────────┐
│ Binding      │  → DefaultBinder
└──────────────┘

Major Extension Points

  • queueSort
  • Controls Pod ordering
  • Example: PrioritySort
  • preFilter, filter, postFilter
  • Removes unsuitable nodes
  • Examples: NodeResourcesFit, NodeAffinity, TaintToleration
  • preScore, score, reserve
  • Ranks remaining nodes
  • Examples: ImageLocality, NodeResourcesFit
  • permit, preBind, bind, postBind
  • Final node assignment
  • Example: DefaultBinder

Plugin Customization Per Profile

Each scheduler profile can customize plugins independently.

You can:

  • Enable specific plugins
  • Disable specific plugins
  • Disable all plugins using "*"
  • Use custom plugins
  • Change filtering and scoring behavior

Tip

Profiles mainly differ by plugin configuration, not just scheduler name.

Key Takeaways

Summary

  • Scheduler Profiles run multiple logical schedulers in one binary
  • Each profile has a unique schedulerName
  • Pods select profiles using schedulerName
  • Profiles customize plugin behavior
  • Reduces operational overhead
  • Avoids multi-scheduler race conditions