Kubernetes- DaemonSet

  A DaemonSet ensures that all (or some) Nodes run a copy of a Pod. As nodes are added to the cluster, Pods are added to them. As nodes are removed from the cluster, those Pods are garbage collected. Deleting a DaemonSet will clean up the Pods it created.

Some typical uses of a DaemonSet are:

  • running a cluster storage daemon on every node
  • running a logs collection daemon on every node
  • running a node monitoring daemon on every node

In a simple case, one DaemonSet, covering all nodes, would be used for each type of daemon. A more complex setup might use multiple DaemonSets for a single type of daemon, but with different flags and/or different memory and cpu requests for different hardware types.


1. Deploy Pod on "all" worker nodes inside k8s cluster using DaemonSet


1a. YAML File:

--------------

# fluentd-ds-allnodes.yaml
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: fluentd-ds
spec:
  template:
    metadata:
      labels:
        name: fluentd
    spec:
      containers:
      - name: fluentd
        image: gcr.io/google-containers/fluentd-elasticsearch:1.20
  selector:
    matchLabels:
      name: fluentd


---------------------------------------------------------------------


1b. Create | Display | Validate


kubectl create -f fluentd-ds-allnodes.yaml

kubectl get po -o wide

kubectl get ds

kubectl describe ds fluentd-ds


*************************************************************************************************************************************************


2. Deploy Pod on "Subset" of worker nodes inside k8s cluster using DaemonSet


----------------------------------------


2a. Attach label to the nodes


kubectl get nodes

kubectl label nodes worker1 worker2 disktype=ssd

kubectl get nodes --show-labels


----------------------------------------


2b. YAML


# nginx-ds-subsetnodes.yaml
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: nginx-ds
spec:
  template:
    metadata:
      labels:
        name: nginx
    spec:
      containers:
      - name: nginx-container
        image: nginx
      nodeSelector:
        disktype: ssd
  selector:
    matchLabels:
      name: nginx



----------------------------------------


2c. Create | Display | Validate


kubectl create -f nginx-ds-subsetnodes.yaml

kubectl get po -o wide

kubectl get ds

kubectl describe ds nginx-ds


********************************************************************************


3. Cleanup


kubectl delete ds fluentd-ds

kubectl delete ds nginx-ds

kubectl get po

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