README.md

Advanced Pod Allocation

Scheduling - Assigning pods to nodes' kubelet can run them. Scheduler - Control plane component that handles scheduling.

Before that it checks

• Resource requests and available node resources.
• Configs that affect scheduling using node labels.

Node Selector - We can configure a nodeSelector for your pods to limit which Node(s) the Pod can be scheduled on. Node selctor use node lables to filter nodes.

Using node name

apiVersion: v1
kind: Pod
metadata:
    name: nginx
spec:
    containers:
    - name: nginx
      image: nginx
    nodeSelector: 
      mylabel: myvalue

nodeName

apiVersion: v1
kind: Pod
metadata:
    name: nginx
spec:
    containers:
    - name: nginx
      image: nginx
    nodeName: k8s-worker1

To label a node

kubectl label nodes <NODE_NAME> <LABEL_NAME>=<LABLE_VALUE>

kubectl label nodes gke-chamod-default-pool-7c9d38c3-89wt special=true

Then the pod looks like below

apiVersion: v1
kind: Pod
metadata:
  name: nodeselector-pod
  labels:
    name: nodeselector-pod
  namespace: dev
spec:
  nodeSelector:
    special: 'true'
  containers:
  - name: nginx
    image: nginx
    resources:
      limits:
        memory: "128Mi"
        cpu: "500m"

Using Node name

apiVersion: v1
kind: Pod
metadata:
  name: nodename-pod
  labels:
    name: nodename-pod
  namespace: dev
spec:
  nodeName: gke-chamod-default-pool-7c9d38c3-89wt
  containers:
  - name: nginx
    image: nginx
    resources:
      limits:
        memory: "128Mi"
        cpu: "500m"

Using DaemonSets

DaemonSet - Automatically runs a copy of a Pod on each node. also run copy of Pod on new nodes as they are added to the cluster.

DaemonSets and Scheduling

We can combine DaemonSet with Scheduling

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: my-daemonset
  namespace: dev
spec:
  selector:
    matchLabels:
      app: my-daemonset
  template:
    metadata:
      labels:
        app: my-daemonset
    spec:
      containers:
        - name: nginx
          image: nginx   

Using Static Pods

Static Pod - A pod that is managed by directly by the kubelet on a node, not by the K8s API server. They can run even if there is no K8s API server present.

Mirror Pod - Kubelet will create a mirror Pod for each static Pod. Mirror allow you to see the status of the static Pod via K8s API. But you cannot change or manage them via API.

sudo vi /etc/kubernetes/manifests/my-static-poy.yaml

apiVersion: v1
kind: Pod
metadata:
  name: my-static-pod
  labels:
    name: my-static-pod
  namespace: dev
spec:
  containers:
  - name: nginx
    image: nginx

Wait till kubernetes detect the file change or simply restart the kubelet

sudo systemctl restart kubelet