The pod pod-s2 cannot be scheduled on the same node as pod-s1. See Inter-pod affinity and anti-affinity in the Kubernetes documentation for details. See nodeSelector in the Kubernetes documentation for details. The node that with highest weight is preferred. If labels on a node change at runtime such that the affinity rules on a pod are no longer met, the pod continues to run on the node. The following diagram illustrates pod anti-affinity flow: Pod affinity is similar to pod anti-affinity with the differences of the topologyKey not being limited to only kubernetes.io/hostname since it can be any label that consistently is placed on all pods. Specifies a weight for a preferred rule. The cluster administrator adds the next layer of constraints by creating one or more provisioners. Learn about scheduling workloads with Karpenter, requiredDuringSchedulingIgnoredDuringExecution, Well-Known Labels, Annotations and Taints, Specify a memory request and a memory limit. The following example demonstrates pod affinity for pods without matching labels and label selectors. containers: - name: ocp If they all fail, Karpenter will fail to provision the pod. In practice tainted nodes will be more like pseudo-reserved nodes, since taints and tolerations wont exclude undesired pods in certain circumstances: Ive set up a 3 node EKS cluster with Pipeline. When the pod is created, Karpenter follows references from the Pod to PersistentVolumeClaim to StorageClass and identifies that this pod requires storage in us-west-2a and us-west-2b. requirements. If there is no other pod with that label, the new pod remains in a pending state: requiredDuringSchedulingIgnoredDuringExecution, preferredDuringSchedulingIgnoredDuringExecution, apiVersion: v1 security: s1 This Kubernetes feature allows users to mark a node (taint the node) so that no pods can be scheduled to it, unless a pod explicitly tolerates the taint. There are two normal pods kube-dns-7cc87d595-wbs7x and tiller-deploy-777677b45c-m9n27 the former running in node ip-192-168-101-21.us-west-2.compute.internal and the latter on ip-192-168-96-47.us-west-2.compute.internal. Pod anti-affinity requires topologyKey to be set and all pods to have labels referenced by topologyKey. docs: fixed inaccurate note about pod affinity (#2074) (c172de00), Needing to run in zones where dependent applications or storage are available, Requiring certain kinds of processors or other hardware, Wanting to use techniques like topology spread to help insure high availability, Pods being spread across zones, hosts, and capacity-type (, No more than one pod difference in the number of pods on each host (. All examples below assume that the provisioner doesnt have constraints to prevent those zones from being used. E.g. In a follow up post we will go into the details of how the Pipeline platform uses these and allows use of the underlying infrastructure in an efficient, automated way. Pods may require nodes with special hardware, isolation, or colocation with other pods running in the system. metadata: Specify a key and value for the label. The following example demonstrates pod anti-affinity for pods with matching labels and label selectors. Since the kube-dns pod is created through a deployment we are going to place the following toleration into the deployments spec: As we can see, the kube-dns pod is still running on node ip-192-168-165-61.us-west-2.compute.internal instead of the tainted ip-192-168-101-21.us-west-2.compute.internal even though we set the appropriate toleration for it. We can see that the kube-dns pod was stopped and started on a different node ip-192-168-165-61.us-west-2.compute.internal: Now if we want to make the kube-dns pod to be schedulable on the tainted ip-192-168-101-21.us-west-2.compute.internal node we need to place the appropriate toleration on the pod. kind: Pod The first constraint says you could use us-west-2a or us-west-2b, the second constraint makes it so only us-west-2b can be used. This leads to pods with label my-label: test being placed on different nodes. The CSI driver creates a PersistentVolume according to the PersistentVolumeClaim and gives it a node affinity rule for us-west-2a. By using the Kubernetes topologySpreadConstraints you can ask the provisioner to have pods push away from each other to limit the blast radius of an outage. First, we change the kube-dns deployment to produce two replicas and remove the earlier set node affinity. In this post we discuss how taints and tolerations, node affinity and pod affinity, anti-affinity work and can be used to instruct the Kubernetes scheduler to place pods on nodes that fulfill their special needs. name: pod-s2 image: docker.io/ocpqe/hello-pod, NAME READY STATUS RESTARTS AGE IP NODE, pod-s2 0/1 Pending 0 32s , Controlling pod placement onto nodes (scheduling), Selecting an installation method and preparing a cluster, Mirroring images for a disconnected installation, Installing a cluster on AWS with customizations, Installing a cluster on AWS with network customizations, Installing a cluster on AWS in a restricted network, Installing a cluster on AWS into an existing VPC, Installing a cluster on AWS into a government or secret region, Installing a cluster on AWS into a China region, Installing a cluster on AWS using CloudFormation templates, Installing a cluster on AWS in a restricted network with user-provisioned infrastructure, Installing a cluster on Azure with customizations, Installing a cluster on Azure with network customizations, Installing a cluster on Azure into an existing VNet, Installing a cluster on Azure into a government region, Installing a cluster on Azure using ARM templates, Manually creating IAM for Azure Stack Hub, Installing a cluster on Azure Stack Hub using ARM templates, Installing a cluster on GCP with customizations, Installing a cluster on GCP with network customizations, Installing a cluster on GCP in a restricted network, Installing a cluster on GCP into an existing VPC, Installing a cluster on GCP using Deployment Manager templates, Installing a cluster into a shared VPC on GCP using Deployment Manager templates, Installing a cluster on GCP in a restricted network with user-provisioned infrastructure, Installing a user-provisioned cluster on bare metal, Installing a user-provisioned bare metal cluster with network customizations, Installing a user-provisioned bare metal cluster on a restricted network, Setting up the environment for an OpenShift installation, Installing a cluster on OpenStack with customizations, Installing a cluster on OpenStack with Kuryr, Installing a cluster that supports SR-IOV compute machines on OpenStack, Installing a cluster on OpenStack on your own infrastructure, Installing a cluster on OpenStack with Kuryr on your own infrastructure, Installing a cluster on OpenStack on your own SR-IOV infrastructure, Installing a cluster on OpenStack in a restricted network, Uninstalling a cluster on OpenStack from your own infrastructure, Installing a cluster on oVirt with customizations, Installing a cluster on oVirt with user-provisioned infrastructure, Installing a cluster on RHV in a restricted network, Installing a cluster on vSphere with customizations, Installing a cluster on vSphere with network customizations, Installing a cluster on vSphere with user-provisioned infrastructure, Installing a cluster on vSphere with user-provisioned infrastructure and network customizations, Installing a cluster on vSphere in a restricted network, Installing a cluster on vSphere in a restricted network with user-provisioned infrastructure, Uninstalling a cluster on vSphere that uses installer-provisioned infrastructure, Using the vSphere Problem Detector Operator, Installing a cluster on VMC with customizations, Installing a cluster on VMC with network customizations, Installing a cluster on VMC in a restricted network, Installing a cluster on VMC with user-provisioned infrastructure, Installing a cluster on VMC with user-provisioned infrastructure and network customizations, Installing a cluster on VMC in a restricted network with user-provisioned infrastructure, Converting a connected cluster to a disconnected cluster, Preparing to perform an EUS-to-EUS update, Performing update using canary rollout strategy, Updating hardware on nodes running on vSphere, Showing data collected by remote health monitoring, Using Insights to identify issues with your cluster, Using remote health reporting in a restricted network, Importing simple content access certificates with Insights Operator, Troubleshooting CRI-O container runtime issues, Troubleshooting the Source-to-Image process, Troubleshooting Windows container workload issues, Extending the OpenShift CLI with plug-ins, OpenShift CLI developer command reference, OpenShift CLI administrator command reference, Knative CLI (kn) for use with OpenShift Serverless, Replacing the default ingress certificate, Securing service traffic using service serving certificates, User-provided certificates for the API server, User-provided certificates for default ingress, Monitoring and cluster logging Operator component certificates, Retrieving Compliance Operator raw results, Performing advanced Compliance Operator tasks, Understanding the Custom Resource Definitions, Understanding the File Integrity Operator, Performing advanced File Integrity Operator tasks, Troubleshooting the File Integrity Operator, Allowing JavaScript-based access to the API server from additional hosts, Authentication and authorization overview, Understanding identity provider configuration, Configuring an HTPasswd identity provider, Configuring a basic authentication identity provider, Configuring a request header identity provider, Configuring a GitHub or GitHub Enterprise identity provider, Configuring an OpenID Connect identity provider, Using RBAC to define and apply permissions, Understanding and creating service accounts, Using a service account as an OAuth client, Understanding the Cluster Network Operator, Defining a default network policy for projects, Removing a pod from an additional network, About Single Root I/O Virtualization (SR-IOV) hardware networks, Configuring an SR-IOV Ethernet network attachment, Configuring an SR-IOV InfiniBand network attachment, About the OpenShift SDN default CNI network provider, Configuring an egress firewall for a project, Removing an egress firewall from a project, Considerations for the use of an egress router pod, Deploying an egress router pod in redirect mode, Deploying an egress router pod in HTTP proxy mode, Deploying an egress router pod in DNS proxy mode, Configuring an egress router pod destination list from a config map, About the OVN-Kubernetes network provider, Migrating from the OpenShift SDN cluster network provider, Rolling back to the OpenShift SDN cluster network provider, Converting to IPv4/IPv6 dual stack networking, Configuring ingress cluster traffic using an Ingress Controller, Configuring ingress cluster traffic using a load balancer, Configuring ingress cluster traffic on AWS using a Network Load Balancer, Configuring ingress cluster traffic using a service external IP, Configuring ingress cluster traffic using a NodePort, Troubleshooting node network configuration, Associating secondary interfaces metrics to network attachments, Persistent storage using AWS Elastic Block Store, Persistent storage using GCE Persistent Disk, Persistent storage using Red Hat OpenShift Container Storage, AWS Elastic Block Store CSI Driver Operator, AWS Elastic File Service CSI Driver Operator, Red Hat Virtualization CSI Driver Operator, Configuring the registry for AWS user-provisioned infrastructure, Configuring the registry for GCP user-provisioned infrastructure, Configuring the registry for Azure user-provisioned infrastructure, Creating applications from installed Operators, Allowing non-cluster administrators to install Operators, Upgrading projects for newer Operator SDK versions, High-availability or single-node cluster detection and support, Configuring built-in monitoring with Prometheus, Migrating package manifest projects to bundle format, Setting up additional trusted certificate authorities for builds, Using the Cluster Samples Operator with an alternate registry, Using image streams with Kubernetes resources, Triggering updates on image stream changes, Creating applications using the Developer perspective, Viewing application composition using the Topology view, Getting started with service binding on IBM Power, IBM Z, and LinuxONE, Binding workloads using Service Binding Operator, Connecting an application to a service using the Developer perspective, Configuring custom Helm chart repositories, Understanding Deployments and DeploymentConfigs, Monitoring project and application metrics using the Developer perspective, Adding compute machines to user-provisioned infrastructure clusters, Adding compute machines to AWS using CloudFormation templates, Automatically scaling pods with the horizontal pod autoscaler, Automatically adjust pod resource levels with the vertical pod autoscaler, Using Device Manager to make devices available to nodes, Including pod priority in pod scheduling decisions, Placing pods on specific nodes using node selectors, Configuring the default scheduler to control pod placement, Scheduling pods using a scheduler profile, Placing pods relative to other pods using pod affinity and anti-affinity rules, Controlling pod placement on nodes using node affinity rules, Controlling pod placement using node taints, Controlling pod placement using pod topology spread constraints, Running background tasks on nodes automatically with daemonsets, Viewing and listing the nodes in your cluster, Managing the maximum number of pods per node, Remediating nodes with the Poison Pill Operator, Deploying node health checks by using the Node Health Check Operator, Freeing node resources using garbage collection, Allocating specific CPUs for nodes in a cluster, Configuring the TLS security profile for the kubelet, Using Init Containers to perform tasks before a pod is deployed, Allowing containers to consume API objects, Using port forwarding to access applications in a container, Viewing system event information in a cluster, Configuring cluster memory to meet container memory and risk requirements, Configuring your cluster to place pods on overcommited nodes, Red Hat OpenShift support for Windows Containers overview, Red Hat OpenShift support for Windows Containers release notes, Understanding Windows container workloads, Creating a Windows MachineSet object on AWS, Creating a Windows MachineSet object on Azure, Creating a Windows MachineSet object on vSphere, Using Bring-Your-Own-Host Windows instances as nodes, About the Cluster Logging custom resource, Configuring CPU and memory limits for Logging components, Using tolerations to control Logging pod placement, Moving the Logging resources with node selectors, Collecting logging data for Red Hat Support, Enabling monitoring for user-defined projects, Planning your environment according to object maximums, What huge pages do and how they are consumed by apps, Performance Addon Operator for low latency nodes, Deploying distributed units manually on single-node OpenShift, Workload partitioning on single-node OpenShift, Deploying distributed units at scale in a disconnected environment, About specialized hardware and driver enablement, Overview of backup and restore operations, Installing and configuring OADP with Azure, Recovering from expired control plane certificates, Installing MTC in a restricted network environment, Editing kubelet log level verbosity and gathering logs, LocalResourceAccessReview [authorization.openshift.io/v1], LocalSubjectAccessReview [authorization.openshift.io/v1], ResourceAccessReview [authorization.openshift.io/v1], SelfSubjectRulesReview [authorization.openshift.io/v1], SubjectAccessReview [authorization.openshift.io/v1], SubjectRulesReview [authorization.openshift.io/v1], LocalSubjectAccessReview [authorization.k8s.io/v1], SelfSubjectAccessReview [authorization.k8s.io/v1], SelfSubjectRulesReview [authorization.k8s.io/v1], SubjectAccessReview [authorization.k8s.io/v1], ClusterAutoscaler [autoscaling.openshift.io/v1], MachineAutoscaler [autoscaling.openshift.io/v1beta1], HelmChartRepository [helm.openshift.io/v1beta1], ConsoleCLIDownload [console.openshift.io/v1], ConsoleExternalLogLink [console.openshift.io/v1], ConsoleNotification [console.openshift.io/v1], ConsolePlugin [console.openshift.io/v1alpha1], ConsoleQuickStart [console.openshift.io/v1], ConsoleYAMLSample [console.openshift.io/v1], CustomResourceDefinition [apiextensions.k8s.io/v1], MutatingWebhookConfiguration [admissionregistration.k8s.io/v1], ValidatingWebhookConfiguration [admissionregistration.k8s.io/v1], ImageStreamImport [image.openshift.io/v1], ImageStreamMapping [image.openshift.io/v1], ContainerRuntimeConfig [machineconfiguration.openshift.io/v1], ControllerConfig [machineconfiguration.openshift.io/v1], KubeletConfig [machineconfiguration.openshift.io/v1], MachineConfigPool [machineconfiguration.openshift.io/v1], MachineConfig [machineconfiguration.openshift.io/v1], MachineHealthCheck [machine.openshift.io/v1beta1], MachineSet [machine.openshift.io/v1beta1], APIRequestCount [apiserver.openshift.io/v1], AlertmanagerConfig [monitoring.coreos.com/v1alpha1], PrometheusRule [monitoring.coreos.com/v1], ServiceMonitor [monitoring.coreos.com/v1], EgressNetworkPolicy [network.openshift.io/v1], EgressRouter [network.operator.openshift.io/v1], IPPool [whereabouts.cni.cncf.io/v1alpha1], NetworkAttachmentDefinition [k8s.cni.cncf.io/v1], PodNetworkConnectivityCheck [controlplane.operator.openshift.io/v1alpha1], OAuthAuthorizeToken [oauth.openshift.io/v1], OAuthClientAuthorization [oauth.openshift.io/v1], UserOAuthAccessToken [oauth.openshift.io/v1], Authentication [operator.openshift.io/v1], CloudCredential [operator.openshift.io/v1], ClusterCSIDriver [operator.openshift.io/v1], Config [imageregistry.operator.openshift.io/v1], Config [samples.operator.openshift.io/v1], CSISnapshotController [operator.openshift.io/v1], DNSRecord [ingress.operator.openshift.io/v1], ImageContentSourcePolicy [operator.openshift.io/v1alpha1], ImagePruner [imageregistry.operator.openshift.io/v1], IngressController [operator.openshift.io/v1], KubeControllerManager [operator.openshift.io/v1], KubeStorageVersionMigrator [operator.openshift.io/v1], OpenShiftAPIServer [operator.openshift.io/v1], OpenShiftControllerManager [operator.openshift.io/v1], OperatorPKI [network.operator.openshift.io/v1], CatalogSource [operators.coreos.com/v1alpha1], ClusterServiceVersion [operators.coreos.com/v1alpha1], InstallPlan [operators.coreos.com/v1alpha1], OperatorCondition [operators.coreos.com/v2], PackageManifest [packages.operators.coreos.com/v1], Subscription [operators.coreos.com/v1alpha1], ClusterRoleBinding [rbac.authorization.k8s.io/v1], ClusterRole [rbac.authorization.k8s.io/v1], RoleBinding [rbac.authorization.k8s.io/v1], ClusterRoleBinding [authorization.openshift.io/v1], ClusterRole [authorization.openshift.io/v1], RoleBindingRestriction [authorization.openshift.io/v1], RoleBinding [authorization.openshift.io/v1], AppliedClusterResourceQuota [quota.openshift.io/v1], ClusterResourceQuota [quota.openshift.io/v1], FlowSchema [flowcontrol.apiserver.k8s.io/v1beta1], PriorityLevelConfiguration [flowcontrol.apiserver.k8s.io/v1beta1], CertificateSigningRequest [certificates.k8s.io/v1], CredentialsRequest [cloudcredential.openshift.io/v1], PodSecurityPolicyReview [security.openshift.io/v1], PodSecurityPolicySelfSubjectReview [security.openshift.io/v1], PodSecurityPolicySubjectReview [security.openshift.io/v1], RangeAllocation [security.openshift.io/v1], SecurityContextConstraints [security.openshift.io/v1], CSIStorageCapacity [storage.k8s.io/v1beta1], StorageVersionMigration [migration.k8s.io/v1alpha1], VolumeSnapshot [snapshot.storage.k8s.io/v1], VolumeSnapshotClass [snapshot.storage.k8s.io/v1], VolumeSnapshotContent [snapshot.storage.k8s.io/v1], BrokerTemplateInstance [template.openshift.io/v1], TemplateInstance [template.openshift.io/v1], UserIdentityMapping [user.openshift.io/v1], Preparing your OKD cluster for OKD Virtualization, Specifying nodes for OKD Virtualization components, Installing OKD Virtualization using the web console, Installing OKD Virtualization using the CLI, Uninstalling OKD Virtualization using the web console, Uninstalling OKD Virtualization using the CLI, Additional security privileges granted for kubevirt-controller and virt-launcher, Triggering virtual machine failover by resolving a failed node, Installing the QEMU guest agent on virtual machines, Viewing the QEMU guest agent information for virtual machines, Managing config maps, secrets, and service accounts in virtual machines, Installing VirtIO driver on an existing Windows virtual machine, Installing VirtIO driver on a new Windows virtual machine, Configuring PXE booting for virtual machines, Enabling dedicated resources for a virtual machine, Importing virtual machine images with data volumes, Importing virtual machine images to block storage with data volumes, Enabling user permissions to clone data volumes across namespaces, Cloning a virtual machine disk into a new data volume, Cloning a virtual machine by using a data volume template, Cloning a virtual machine disk into a new block storage data volume, Configuring the virtual machine for the default pod network with OKD Virtualization, Attaching a virtual machine to a Linux bridge network, Configuring IP addresses for virtual machines, Configuring an SR-IOV network device for virtual machines, Attaching a virtual machine to an SR-IOV network, Viewing the IP address of NICs on a virtual machine, Using a MAC address pool for virtual machines, Configuring local storage for virtual machines, Reserving PVC space for file system overhead, Configuring CDI to work with namespaces that have a compute resource quota, Uploading local disk images by using the web console, Uploading local disk images by using the virtctl tool, Uploading a local disk image to a block storage data volume, Moving a local virtual machine disk to a different node, Expanding virtual storage by adding blank disk images, Cloning a data volume using smart-cloning, Using container disks with virtual machines, Re-using statically provisioned persistent volumes, Enabling dedicated resources for a virtual machine template, Migrating a virtual machine instance to another node, Monitoring live migration of a virtual machine instance, Cancelling the live migration of a virtual machine instance, Configuring virtual machine eviction strategy, Managing node labeling for obsolete CPU models, Diagnosing data volumes using events and conditions, Viewing information about virtual machine workloads, Reviewing resource usage by virtual machines, OpenShift cluster monitoring, logging, and Telemetry, Sample pod affinity and anti-affinity rules. For example: In this example, the container is requesting 128MiB of memory and .5 CPU. requiredDuringSchedulingIgnoredDuringExecution: kube-dns-669db795bb-5blv2 3/3 Running, kube-dns-55ccbc9fc-8xjfg 3/3 Running, kube-dns-55ccbc9fc-ms577 3/3 Running, kube-dns-85945db57c-kk288 3/3 Running, kube-dns-85945db57c-pzw2b 3/3 Running. kind: Pod This is by design, as system pods are required by the Kubernetes infrastructure (e.g. In the next post we will describe the features that Pipeline provides to our user and how these rely on taints and tolerations, node affinity and pod affinity/anti-affinity, so stay tuned. The following steps demonstrate a simple two-pod configuration that creates pod with a label and a pod that uses an anti-affinity preferred rule to attempt to prevent scheduling with that pod. name: pod-s1 This time, Karpenter identifies that a PersistentVolume already exists for the PersistentVolumeClaim, and includes its zone us-west-2a in the pods scheduling requirements. The question of which node is up to the Kubernetes scheduler (in this case its ip-192-168-165-61.us-west-2.compute.internal).
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