Resourcelimitrequestquota

🔑 What Are `requests` and `limits`?

requests
limits
resource quotas
limit ranges

Each with practical YAML examples and common use cases.

Term	Description
`requests`	Minimum resources a container is guaranteed
`limits`	Maximum resources a container can use

If a container exceeds limits, it may be throttled (cpu) or killed (memory).

🧪 Real-World Example: Pod with Requests and Limits

apiVersion: v1
kind: Pod
metadata:
  name: app-with-resources
spec:
  containers:
  - name: app
    image: nginx
    resources:
      requests:
        memory: "128Mi"
        cpu: "250m"
      limits:
        memory: "256Mi"
        cpu: "500m"

✅ What this means:

Pod is guaranteed 128Mi memory & 250m CPU.
It can use up to 256Mi memory and 500m CPU.
If it uses more memory → it gets OOMKilled.

⚖️ Use Case: Resource Control on Shared Cluster

In multi-tenant clusters, you want:

Predictable resource usage
Prevent one team from starving others
Apply limits to all pods

🔐 1. ResourceQuota (Namespace-level enforcement)

apiVersion: v1
kind: ResourceQuota
metadata:
  name: team-a-quota
  namespace: team-a
spec:
  hard:
    requests.cpu: "2"
    requests.memory: "4Gi"
    limits.cpu: "4"
    limits.memory: "8Gi"
    pods: "10"

✅ Effect: In the team-a namespace:

Max of 10 pods
Total requests.cpu must not exceed 2 cores
Total limits.memory must not exceed 8Gi

🚧 2. LimitRange (Enforce defaults and max/min per pod/container)

apiVersion: v1
kind: LimitRange
metadata:
  name: container-defaults
  namespace: dev
spec:
  limits:
  - default:
      cpu: 500m
      memory: 512Mi
    defaultRequest:
      cpu: 200m
      memory: 256Mi
    max:
      cpu: 1
      memory: 1Gi
    min:
      cpu: 100m
      memory: 128Mi
    type: Container

✅ Effect:

If pod does not specify resources → gets defaults (500m, 512Mi)
Cannot request more than 1 CPU or less than 100m
Helps standardize resource use

🧩 Example Use Case Summary

Use Case	Feature	Example
Guarantee app gets minimum resources	`requests`	`cpu: 200m`
Prevent app from hogging resources	`limits`	`memory: 1Gi`
Restrict total resource usage	`ResourceQuota`	`limits.cpu: 4`
Enforce per-pod default/max values	`LimitRange`	`default: 500m`
Avoid defining requests manually	`LimitRange` with `defaultRequest`	Auto-applies

🔍 View Resource Usage

Check namespace quota:

kubectl describe quota -n team-a

Check LimitRanges:

kubectl get limitrange -n dev

📦 Full Example: LimitRange + Quota + Pod

# 1. Resource Quota
apiVersion: v1
kind: ResourceQuota
metadata:
  name: my-quota
  namespace: myspace
spec:
  hard:
    pods: "5"
    requests.cpu: "1"
    requests.memory: "1Gi"
    limits.cpu: "2"
    limits.memory: "2Gi"
---
# 2. Limit Range
apiVersion: v1
kind: LimitRange
metadata:
  name: defaults
  namespace: myspace
spec:
  limits:
  - default:
      cpu: 500m
      memory: 512Mi
    defaultRequest:
      cpu: 200m
      memory: 256Mi
    type: Container
---
# 3. Pod (No resources set — will use defaults)
apiVersion: v1
kind: Pod
metadata:
  name: app
  namespace: myspace
spec:
  containers:
  - name: nginx
    image: nginx

✅ Result:

Pod will auto inherit 200m request and 500m limit from LimitRange.
Quota ensures you don’t exceed total 2 CPU / 2Gi.

🧠 Tips

Tip	Description
💡 Always define `requests` and `limits`	Helps scheduler make better decisions
📊 Use `kubectl top` to check usage	Install Metrics Server
✅ Use LimitRanges in dev namespaces	Prevent accidental resource abuse
🔐 Use Quotas in production namespaces	Protect cluster-wide limits

Probes Taintstoleration

🔑 What Are requests and limits?