[Kubernetes] Multiple Schedulers & Scheduler Profiles

📌 1. Multiple Schedulers in Kubernetes

Normally, a Kubernetes cluster uses one scheduler: the default kube-scheduler.

 

But Kubernetes allows multiple schedulers to coexist!

Meaning, you can deploy and run custom schedulers alongside the default one.

 

🔹 How it works:

• A Pod can specify which scheduler it wants by setting the schedulerName field in its spec.
• Based on the schedulerName, Kubernetes dispatches the Pod to the appropriate scheduler.

🔹 Use cases:

• Specialized workloads (e.g., AI jobs needing GPU scheduling)
• Multi-tenancy (different teams use different scheduling rules)
• Testing new scheduling algorithms without disrupting existing workloads

🔹 Example:

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

→ Here, only `my-custom-scheduler` will attempt to schedule this pod.

 

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📌 2. Scheduler Profiles (within the Default Scheduler)

Scheduler Profiles allow you to configure multiple scheduling behaviors within one single kube-scheduler instance (not spinning up multiple processes).

 

Since Kubernetes v1.19, you can define multiple profiles under the same kube-scheduler configuration.

🔹 How it works:

• Each profile has its own scheduling policies (e.g., plugins enabled/disabled, weights set differently).
• A Pod selects a profile by setting the schedulerName field.
• One kube-scheduler process handles all the profiles internally.

🔹 Why use profiles?

• Reduce resource overhead (single scheduler process, multiple behaviors)
• Fine-tune scheduling logic for different classes of workloads
• Support various SLA (Service Level Agreement) requirements

🔹 Example configuration (kube-scheduler config file):

apiVersion: kubescheduler.config.k8s.io/v1
kind: KubeSchedulerConfiguration
profiles:
- schedulerName: default-scheduler
  plugins:
    score:
      enabled:
      - name: NodeResourcesBalancedAllocation
- schedulerName: high-priority-scheduler
  plugins:
    score:
      enabled:
      - name: NodeResourcesLeastAllocated

i. Pods with schedulerName: `default-scheduler` use NodeResourcesBalancedAllocation.

ii. Pods with schedulerName: `high-priority-scheduler` use NodeResourcesLeastAllocated.

 

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✨ Quick Visual Summary

Concept	Multiple Scheduler	Scheduler Profiles
Definition	Run separate scheduler binaries	One scheduler binary, multiple behaviors
Pod Field	spec.schedulerName	spec.schedulerName
Resource Usage	Higher (multiple processes)	Lower (single process)
Typical Use	Custom algorithms, experiments	Different scheduling rules for workload classes
Config location	Separate binaries/deployments	Single kube-scheduler config

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참고 자료

 - Configure Multiple Schedulers | Kubernetes

 

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