Configure workload separation in GKE

This page shows you how to tell Google Kubernetes Engine (GKE) to schedule your Pods together, separately, or in specific locations.

Workload separation lets you use taints and tolerations to tell GKE to separate Pods onto different nodes, place Pods on nodes that meet specific criteria, or to schedule specific workloads together. What you need to do to configure workload separation depends on your GKE cluster configuration. The following table describes the differences:

Workload separation configuration

Add a toleration for a specific key:value pair to your Pod specification, and select that key:value pair using a nodeSelector. GKE creates nodes, applies the corresponding node taint, and schedules the Pod on the node.

For instructions, refer to Separate workloads in Autopilot clusters on this page.
Standard without node auto-provisioning
  1. Create a node pool with a node taint and a node label
  2. Add a toleration for that taint to the Pod specification

For instructions, refer to Isolate your workloads in dedicated node pools.

This guide uses an example scenario in which you have two workloads, a batch job and a web server, that you want to separate from each other.

When to use workload separation in GKE

Workload separation is useful when you have workloads that perform different roles and shouldn't run on the same underlying machines. Some example scenarios include the following:

  • You have a batch coordinator workload that creates Jobs that you want to keep separate.
  • You run a game server with a matchmaking workload that you want to separate from session Pods.
  • You want to separate parts of your stack from each other, such as separating a server from a database.
  • You want to separate some workloads for compliance or policy reasons.

Pricing

In Autopilot clusters, you're billed for the resources that your Pods request while running. For details, refer to Autopilot pricing. Pods that use workload separation have higher minimum resource requests enforced than regular Pods.

In Standard clusters, you're billed based on the hardware configuration and size of each node, regardless of whether Pods are running on the nodes. For details, refer to Standard pricing.

Before you begin

Before you start, make sure you have performed the following tasks:

  • Enable the Google Kubernetes Engine API.
    • Enable Google Kubernetes Engine API
  • If you want to use the Google Cloud CLI for this task, install and then initialize the gcloud CLI. If you previously installed the gcloud CLI, get the latest version by running gcloud components update.

Separate workloads in Autopilot clusters

To separate workloads from each other, add a toleration and a node selector to each workload specification that defines the node on which the workload should run. This method also works on Standard clusters that have node auto-provisioning enabled.

  1. Save the following manifest as web-server.yaml:

    apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-server
spec:
  replicas: 6
  selector:
    matchLabels:
      pod: nginx-pod
  template:
    metadata:
      labels:
        pod: nginx-pod
    spec:
      tolerations:
      - key: group
        operator: Equal
        value: "servers"
        effect: NoSchedule
      nodeSelector:
        group: "servers"
      containers:
      - name: web-server
        image: nginx

    This manifest includes the following fields:

    • spec.tolerations: GKE can place the Pods on nodes that have the group=servers:NoSchedule taint. GKE can't schedule Pods that don't have this toleration on those nodes.
    • spec.nodeSelector: GKE must place the Pods on nodes that have the group: servers node label.

    GKE adds the corresponding labels and taints to nodes that GKE automatically provisions to run these Pods.

  2. Save the following manifest as batch-job.yaml:

    apiVersion: batch/v1
kind: Job
metadata:
  name: batch-job
spec:
  completions: 5
  backoffLimit: 3
  ttlSecondsAfterFinished: 120
  template:
    metadata:
      labels:
        pod: pi-pod
    spec:
      restartPolicy: Never
      tolerations:
      - key: group
        operator: Equal
        value: "jobs"
        effect: NoSchedule
      nodeSelector:
        group: "jobs"
      containers:
      - name: pi
        image: perl
        command: ["perl",  "-Mbignum=bpi", "-wle", "print bpi(2000)"]

    This manifest includes the following fields:

    • spec.tolerations: GKE can place the Pods on nodes that have the group=jobs:NoSchedule taint. GKE can't schedule Pods that don't have this toleration on those nodes.
    • spec.nodeSelector: GKE must place the Pods on nodes that have the group: jobs node label.

    GKE adds the corresponding labels and taints to nodes that GKE automatically provisions to run these Pods.

  3. Deploy the workloads:

    kubectl apply -f batch-job.yaml web-server.yaml

When you deploy the workloads, GKE does the following for each workload:

  1. GKE looks for existing nodes that have the corresponding node taint and node label specified in the manifest. If nodes exist and have available resources, GKE schedules the workload on the node.
  2. If GKE doesn't find an eligible existing node to schedule the workload, GKE creates a new node and applies the corresponding node taint and node label based on the manifest. GKE places the Pod on the new node.

The presence of the NoSchedule effect in the node taint ensures that workloads without a toleration don't get placed on the node.

Verify the workload separation

List your Pods to find the names of the nodes:

kubectl get pods --output=wide

The output is similar to the following:

NAME                          READY   ...   NODE
batch-job-28j9h               0/1     ...   gk3-sandbox-autopilot-nap-1hzelof0-ed737889-2m59
batch-job-78rcn               0/1     ...   gk3-sandbox-autopilot-nap-1hzelof0-ed737889-2m59
batch-job-gg4x2               0/1     ...   gk3-sandbox-autopilot-nap-1hzelof0-ed737889-2m59
batch-job-qgsxh               0/1     ...   gk3-sandbox-autopilot-nap-1hzelof0-ed737889-2m59
batch-job-v4ksf               0/1     ...   gk3-sandbox-autopilot-nap-1hzelof0-ed737889-2m59
web-server-6bb8cd79b5-dw4ds   1/1     ...   gk3-sandbox-autopilot-nap-1eurxgsq-f2f3c272-n6xm
web-server-6bb8cd79b5-g5ld6   1/1     ...   gk3-sandbox-autopilot-nap-1eurxgsq-9f447e18-275z
web-server-6bb8cd79b5-jcdx5   1/1     ...   gk3-sandbox-autopilot-nap-1eurxgsq-9f447e18-275z
web-server-6bb8cd79b5-pxdzw   1/1     ...   gk3-sandbox-autopilot-nap-1eurxgsq-ccd22fd9-qtfq
web-server-6bb8cd79b5-s66rw   1/1     ...   gk3-sandbox-autopilot-nap-1eurxgsq-ccd22fd9-qtfq
web-server-6bb8cd79b5-zq8hh   1/1     ...   gk3-sandbox-autopilot-nap-1eurxgsq-f2f3c272-n6xm

This output shows that the batch-job Pods and the web-server Pods always run on different nodes.

Limitations of workload separation with taints and tolerations

You can't use the following key prefixes for workload separation:

  • GKE and Kubernetes-specific keys
  • *cloud.google.com/
  • *kubelet.kubernetes.io/
  • *node.kubernetes.io/

You should use your own, unique keys for workload separation.

Separate workloads in Standard clusters without node auto-provisioning

Separating workloads in Standard clusters without node auto-provisioning requires that you manually create node pools with the appropriate node taints and node labels to accommodate your workloads. For instructions, refer to Isolate your workloads in dedicated node pools. Only use this approach if you have specific requirements that require you to manually manage your node pools.

Create a cluster with node taints

When you create a cluster in GKE, you can assign node taints to the cluster. This assigns the taints to all nodes created with the cluster.

If you create a node pool, the node pool does not inherit taints from the cluster. If you want taints on the node pool, you must use the --node-taints flag when you create the node pool.

If you create a Standard cluster with node taints that have the NoSchedule effect or the NoExecute effect, GKE can't schedule some GKE managed components, such as kube-dns or metrics-server on the default node pool that GKE creates when you create the cluster. GKE can't schedule these components because they don't have the corresponding tolerations for your node taints. You must add a new node pool that satisfies one of the following conditions:

  • No taints
  • A taint that has the PreferNoSchedule effect
  • The components.gke.io/gke-managed-components=true:NoSchedule taint

Any of these conditions allow GKE to schedule GKE managed components in the new node pool.

For instructions, refer to Isolate workloads on dedicated nodes.

gcloud

Create a cluster with node taints:

gcloud container clusters create CLUSTER_NAME \
    --node-taints KEY=VALUE:EFFECT

Replace the following:

  • CLUSTER_NAME: the name of the new cluster.
  • EFFECT: one of the following effects: PreferNoSchedule, NoSchedule, or NoExecute.
  • KEY=VALUE: a key-value pair associated with the EFFECT.

Console

Create a cluster with node taints:

  1. Go to the Google Kubernetes Engine page in the Google Cloud console.

    Go to Google Kubernetes Engine

  2. Click Create.

  3. Configure your cluster as desired.

  4. From the navigation pane, under Node Pools, expand the node pool you want to modify, and then click Metadata.

  5. In the Node taints section, click Add Taint.

  6. In the Effect drop-down list, select the desired effect.

  7. Enter the desired key-value pair in the Key and Value fields.

  8. Click Create.

API

When you use the API to create a cluster, include the nodeTaints field under `nodeConfig:

POST https://container.googleapis.com/v1/projects/PROJECT_ID/zones/COMPUTE_ZONE/clusters

{
  'cluster': {
    'name': 'example-cluster',
    'nodeConfig': {
      'nodeTaints': [
        {
          'key': 'special',
          'Value': 'gpu',
          'effect': 'PreferNoSchedule'
        }
      ]
      ...
    }
    ...
  }
}

Remove all taints from a node pool

To remove all taints from a node pool, run the following command:

gcloud beta container node-pools update POOL_NAME \
    --node-taints="" \
    --cluster=CLUSTER_NAME

Replace the following:

  • POOL_NAME: the name of the node pool to change.
  • CLUSTER_NAME: the name of the cluster of the node pool.

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