Understanding Kubernetes Requests & Limits 🚀🔧

🏙️ What's the Deal with Requests & Limits?

Think of your Kubernetes cluster as a bustling city and pods as tenants in an apartment building. Each tenant (pod) requires specific resources like CPU and memory to function:

• Requests: This is the minimum amount of resources a pod needs to operate smoothly. Think of it as a guaranteed reservation for the pod.

• Limits: This is the maximum amount of resources a pod can use. It acts as a safety cap to prevent any pod from consuming more than its fair share and disrupting others.

Why are Requests & Limits Important?

• Resource Control: By setting limits, you prevent a single pod from monopolizing resources, which can lead to issues like out-of-memory (OOM) kills or CPU starvation. ☠️ Why OOM can be a good thing? Because it kills the pod; otherwise, the container would have consumed all the memory and could kill the node. Killing the pod is a better option than killing a node itself.

• Predictability: Requests help the scheduler allocate resources efficiently and ensure pods have the necessary resources to run effectively.

1. Exceeding Available Memory: A pod requesting more memory than is available will be killed due to an OOM (Out of Memory) error.

apiVersion: v1
kind: Pod
metadata:
 name: memory-demo-2
 namespace: mem-example
spec:
 containers:
 - name: memory-demo-2-ctr
   image: polinux/stress
   resources:
     requests:
       memory: "50Mi"
     limits:
       memory: "100Mi"
   command: ["stress"]
   args: ["--vm", "1", "--vm-bytes", "250M", "--vm-hang", "1"]

2. The Below pod will be scheduled

apiVersion: v1
kind: Pod
metadata:
  name: memory-demo
  namespace: mem-example
spec:
  containers:
  - name: memory-demo-ctr
    image: polinux/stress
    resources:
      requests:
        memory: "100Mi"
      limits:
        memory: "200Mi"
    command: ["stress"]
    args: ["--vm", "1", "--vm-bytes", "150M", "--vm-hang", "1"]