> ## Documentation Index > Fetch the complete documentation index at: https://cockroachlabs.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Pod Scheduling with the CockroachDB Operator export const InternalLink = ({version, path = "", children, ...props}) => { let detectedVersion = version || "stable"; if (typeof window !== 'undefined' && !version) { const match = window.location.pathname.match(/\/docs\/([^/]+)/); if (match) { detectedVersion = match[1]; } } const normalizedPath = path.startsWith("/") ? path.slice(1) : path; return {children} ; }; This page describes how to configure pod scheduling settings. These settings control how CockroachDB pods should be identified or scheduled onto worker nodes, which are then proxied to the Kubernetes scheduler. The CockroachDB operator is in Preview. ## Node selectors A pod with a *node selector* will be scheduled onto a worker node that has matching [labels](https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/), or key-value pairs. Specify the labels in `cockroachdb.crdbCluster.podTemplate.spec.nodeSelector` in the values file used to deploy the cluster. If you specify multiple `nodeSelector` labels, the node must match all of them. The following configuration causes CockroachDB pods to be scheduled onto worker nodes that have *both* the labels `worker-pool-name=crdb-workers` and `kubernetes.io/arch=amd64`: ```yaml theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} cockroachdb: crdbCluster: podTemplate: spec: nodeSelector: worker-pool-name: crdb-workers kubernetes.io/arch: amd64 ``` For an example of labeling nodes, see [Scheduling CockroachDB onto labeled nodes](#example-scheduling-cockroachdb-onto-labeled-nodes). ## Affinities and anti-affinities A pod with a *node affinity* seeks out worker nodes that have matching [labels](https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/). A pod with a *pod affinity* seeks out pods that have matching labels. A pod with a *pod anti-affinity* avoids pods that have matching labels. Affinities and anti-affinities can be used together with `operator` fields to: * Require CockroachDB pods to be scheduled onto a labeled worker node. * Require CockroachDB pods to be co-located with labeled pods (e.g., on a node or region). * Prevent CockroachDB pods from being scheduled onto a labeled worker node. * Prevent CockroachDB pods from being co-located with labeled pods (e.g., on a node or region). For an example, see [Scheduling CockroachDB onto labeled nodes](#example-scheduling-cockroachdb-onto-labeled-nodes). ### Add a node affinity Specify node affinities in `cockroachdb.crdbCluster.podTemplate.spec.affinity.nodeAffinity` in the values file used to deploy the cluster. If you specify multiple `matchExpressions` labels, the node must match all of them. If you specify multiple `values` for a label, the node can match any of the values. The following configuration requires that CockroachDB pods are scheduled onto worker nodes running a Linux operating system, with a preference against worker nodes in the `us-east4-b` availability zone. ```yaml theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} cockroachdb: crdbCluster: podTemplate: spec: affinity: nodeAffinity: requiredDuringSchedulingIgnoredDuringExecution: nodeSelectorTerms: - matchExpressions: - key: kubernetes.io/os operator: In values: - linux preferredDuringSchedulingIgnoredDuringExecution: - weight: 100 preference: matchExpressions: - key: topology.kubernetes.io/zone operator: NotIn values: - us-east4-b ``` The `requiredDuringSchedulingIgnoredDuringExecution` node affinity rule, using the `In` operator, requires CockroachDB pods to be scheduled onto nodes with the matching label `kubernetes.io/os=linux`. It will not evict pods that are already running on nodes that do not match the affinity requirements. The `preferredDuringSchedulingIgnoredDuringExecution` node affinity rule, using the `NotIn` operator and specified `weight`, discourages (but does not disallow) CockroachDB pods from being scheduled onto nodes with the label `topology.kubernetes.io/zone=us-east4-b`. This achieves a similar effect as a `PreferNoSchedule` [taint](#taints-and-tolerations). For more context on how these rules work, see the [Kubernetes documentation](https://kubernetes.io/docs/concepts/scheduling-eviction/assign-pod-node/). The [custom resource definition](https://github.com/cockroachdb/helm-charts/blob/master/cockroachdb-parent/charts/cockroachdb/values.yaml) details the fields supported by the operator. ### Add a pod affinity or anti-affinity Specify pod affinities and node anti-affinities in `cockroachdb.crdbCluster.podTemplate.spec.affinity.podAffinity` and `cockroachdb.crdbCluster.podTemplate.spec.affinity.podAntiAffinity` in the values file used to deploy the cluster. If you specify multiple `matchExpressions` labels, the node must match all of them. If you specify multiple `values` for a label, the node can match any of the values. The hard-codes the pod template to only allow one pod per Kubernetes node. If you need to override this value, you can override the pod template. The following configuration attempts to schedule CockroachDB pods in the same zones as the pods that run our example load generator app. It disallows CockroachDB pods from being co-located on the same worker node. ```yaml theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} cockroachdb: crdbCluster: podTemplate: spec: affinity: podAffinity: preferredDuringSchedulingIgnoredDuringExecution: - weight: 100 podAffinityTerm: labelSelector: matchExpressions: - key: app operator: In values: - loadgen topologyKey: topology.kubernetes.io/zone podAntiAffinity: requiredDuringSchedulingIgnoredDuringExecution: - labelSelector: matchExpressions: - key: app.kubernetes.io/instance operator: In values: - cockroachdb topologyKey: kubernetes.io/hostname ``` The `preferredDuringSchedulingIgnoredDuringExecution` pod affinity rule, using the `In` operator and specified `weight`, encourages (but does not require) CockroachDB pods to be co-located with pods labeled `app=loadgen` already running in the same zone, as specified with `topologyKey`. The `requiredDuringSchedulingIgnoredDuringExecution` pod anti-affinity rule, using the `In` operator, requires CockroachDB pods not to be co-located on a worker node, as specified with `topologyKey`. For more context on how these rules work, see the [Kubernetes documentation](https://kubernetes.io/docs/concepts/scheduling-eviction/assign-pod-node/). The [custom resource definition](https://github.com/cockroachdb/helm-charts/blob/master/cockroachdb-parent/charts/cockroachdb/values.yaml) details the fields supported by the operator. ### Example: Scheduling CockroachDB onto labeled nodes In this example, CockroachDB has not yet been deployed to a running Kubernetes cluster. Use a combination of node affinity and pod anti-affinity rules to schedule 3 CockroachDB pods onto three labeled worker nodes. 1. List the worker nodes on the running Kubernetes cluster: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} kubectl get nodes ``` ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} NAME STATUS ROLES AGE VERSION gke-cockroachdb-default-pool-263138a5-kp3v Ready 3m56s v1.20.10-gke.301 gke-cockroachdb-default-pool-263138a5-nn62 Ready 3m56s v1.20.10-gke.301 gke-cockroachdb-default-pool-41796213-75c9 Ready 3m56s v1.20.10-gke.301 gke-cockroachdb-default-pool-41796213-bw3z Ready 3m54s v1.20.10-gke.301 gke-cockroachdb-default-pool-ccd74623-dghs Ready 3m54s v1.20.10-gke.301 gke-cockroachdb-default-pool-ccd74623-p5mf Ready 3m55s v1.20.10-gke.301 ``` 2. Add a `node=crdb` label to three of the running worker nodes. ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} kubectl label nodes gke-cockroachdb-default-pool-263138a5-kp3v gke-cockroachdb-default-pool-41796213-75c9 gke-cockroachdb-default-pool-ccd74623-dghs node=crdb ``` ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} node/gke-cockroachdb-default-pool-5726e554-77r7 labeled node/gke-cockroachdb-default-pool-ee4d4d67-0922 labeled node/gke-cockroachdb-default-pool-ee4d4d67-w18b labeled ``` In this example, 6 GKE nodes are deployed in 3 [node pools](https://cloud.google.com/kubernetes-engine/docs/concepts/node-pools), and each node pool resides in a separate availability zone. To maintain an even distribution of CockroachDB pods as specified in our topology recommendations, each of the 3 labeled worker nodes must belong to a different node pool. This also ensures that the CockroachDB pods, which will be bound to persistent volumes in the same three availability zones, can be scheduled onto worker nodes in their respective zones. 1. Add the following rules to the values file used to deploy the cluster: ```yaml theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} cockroachdb: crdbCluster: podTemplate: spec: affinity: nodeAffinity: requiredDuringSchedulingIgnoredDuringExecution: nodeSelectorTerms: - matchExpressions: - key: node operator: In values: - crdb podAntiAffinity: requiredDuringSchedulingIgnoredDuringExecution: - labelSelector: matchExpressions: - key: app.kubernetes.io/instance operator: In values: - cockroachdb topologyKey: kubernetes.io/hostname ``` The `nodeAffinity` rule requires CockroachDB pods to be scheduled onto worker nodes with the label `node=crdb`. The `podAntiAffinity` rule requires CockroachDB pods not to be co-located on a worker node, as specified with `topologyKey`. 2. Apply the settings to the cluster: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} helm upgrade --reuse-values $CRDBCLUSTER ./cockroachdb-parent/charts/cockroachdb --values ./cockroachdb-parent/charts/cockroachdb/values.yaml -n $NAMESPACE ``` 3. The CockroachDB pods will be deployed to the 3 labeled nodes. To observe this, run: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} kubectl get pods -o wide ``` ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES cockroach-operator-bfdbfc9c7-tbpsw 1/1 Running 0 171m 10.32.2.4 gke-cockroachdb-default-pool-263138a5-kp3v cockroachdb-0 1/1 Running 0 100s 10.32.4.10 gke-cockroachdb-default-pool-ccd74623-dghs cockroachdb-1 1/1 Running 0 100s 10.32.2.6 gke-cockroachdb-default-pool-263138a5-kp3v cockroachdb-2 1/1 Running 0 100s 10.32.0.5 gke-cockroachdb-default-pool-41796213-75c9 ``` ## Taints and tolerations When a *taint* is added to a Kubernetes worker node, pods are prevented from being scheduled onto that node. This effect is ignored by adding a *toleration* to a pod that specifies a matching taint. Taints and tolerations are useful if you want to: * Prevent CockroachDB pods from being scheduled onto a labeled worker node. * Evict CockroachDB pods from a labeled worker node on which they are currently running. For an example, see [Evicting CockroachDB from a running worker node](#example-evicting-cockroachdb-from-a-running-worker-node). ### Add a toleration Specify pod tolerations in the `cockroachdb.crdbCluster.podTemplate.spec.tolerations` object in the values file used to deploy the cluster. The following toleration matches a taint with the specified key, value, and `NoSchedule` effect, using the `Equal` operator. A toleration that uses the `Equal` operator must include a `value` field: ```yaml theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} cockroachdb: crdbCluster: podTemplate: spec: tolerations: - key: "test" operator: "Equal" value: "example" effect: "NoSchedule" ``` A `NoSchedule` taint on a node prevents pods from being scheduled onto the node. The matching toleration allows a pod to be scheduled onto the node. A `NoSchedule` toleration is therefore best included before deploying the cluster. A `PreferNoSchedule` taint discourages, but does not disallow, pods from being scheduled onto the node. The following toleration matches every taint with the specified key and `NoExecute` effect, using the `Exists` operator. A toleration that uses the `Exists` operator must exclude a `value` field: ```yaml theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} cockroachdb: crdbCluster: podTemplate: spec: tolerations: - key: "test" operator: "Exists" effect: "NoExecute" tolerationSeconds: 3600 ``` A `NoExecute` taint on a node prevents pods from being scheduled onto the node, and evicts pods from the node if they are already running on the node. The matching toleration allows a pod to be scheduled onto the node, and to continue running on the node if `tolerationSeconds` is not specified. If `tolerationSeconds` is specified, the pod is evicted after this number of seconds. For more information on using taints and tolerations, see the [Kubernetes documentation](https://kubernetes.io/docs/concepts/scheduling-eviction/taint-and-toleration/). The [custom resource definition](https://github.com/cockroachdb/helm-charts/blob/master/cockroachdb-parent/charts/cockroachdb/values.yaml) details the fields supported by the operator. ### Example: Evicting CockroachDB from a running worker node In this example, CockroachDB has already been deployed on a Kubernetes cluster. Use the `NoExecute` effect to evict one of the CockroachDB pods from its worker node. 1. List the worker nodes on the running Kubernetes cluster: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} kubectl get nodes ``` ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} NAME STATUS ROLES AGE VERSION gke-cockroachdb-default-pool-4e5ce539-68p5 Ready 56m v1.20.9-gke.1001 gke-cockroachdb-default-pool-4e5ce539-j1h1 Ready 56m v1.20.9-gke.1001 gke-cockroachdb-default-pool-95fde00d-173d Ready 56m v1.20.9-gke.1001 gke-cockroachdb-default-pool-95fde00d-hw04 Ready 56m v1.20.9-gke.1001 gke-cockroachdb-default-pool-eb2b2889-q15v Ready 56m v1.20.9-gke.1001 gke-cockroachdb-default-pool-eb2b2889-q704 Ready 56m v1.20.9-gke.1001 ``` 2. Add a taint to a running worker node: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} kubectl taint nodes gke-cockroachdb-default-pool-4e5ce539-j1h1 test=example:NoExecute ``` ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} node/gke-cockroachdb-default-pool-4e5ce539-j1h1 tainted ``` 3. Add a matching tolerations object in the values file used to deploy the cluster. ```yaml theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} cockroachdb: crdbCluster: podTemplate: spec: tolerations: - key: "test" operator: "Exists" effect: "NoExecute" ``` Because no tolerationSeconds is specified, CockroachDB will be evicted immediately from the tainted worker node. 4. Apply the new settings to the cluster: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} helm upgrade --reuse-values $CRDBCLUSTER ./cockroachdb-parent/charts/cockroachdb --values ./cockroachdb-parent/charts/cockroachdb/values.yaml -n $NAMESPACE ``` 5. The CockroachDB pod running on the tainted node (in this case, cockroachdb-2) will be evicted and started on a different worker node. To observe this: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} kubectl get pods -o wide ``` ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES cockroach-operator-c9fc6cb5c-bl6rs 1/1 Running 0 44m 10.32.2.4 gke-cockroachdb-default-pool-4e5ce539-68p5 cockroachdb-0 1/1 Running 0 9m21s 10.32.4.10 gke-cockroachdb-default-pool-95fde00d-173d cockroachdb-1 1/1 Running 0 9m21s 10.32.2.6 gke-cockroachdb-default-pool-eb2b2889-q15v cockroachdb-2 0/1 Running 0 6s 10.32.0.5 gke-cockroachdb-default-pool-4e5ce539-68p5 ``` `cockroachdb-2` is now scheduled onto the `gke-cockroachdb-default-pool-4e5ce539-68p5` node. ## Topology spread constraints A pod with a *topology spread constraint* must satisfy its conditions when being deployed to a given topology. This is used to control the degree to which pods are unevenly distributed across failure domains. ### Add a topology spread constraint Specify pod topology spread constraints in the `cockroachdb.crdbCluster.podTemplate.spec.topologySpreadConstraints` object of the values file used to deploy the cluster. If you specify multiple `topologySpreadConstraints` objects, the matching pods must satisfy all of the constraints. The following topology spread constraint ensures that CockroachDB pods deployed with the label `environment=production` will not be unevenly distributed across zones by more than `1` pod: ```yaml theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} cockroachdb: crdbCluster: podTemplate: spec: topologySpreadConstraints: - maxSkew: 1 topologyKey: topology.kubernetes.io/zone whenUnsatisfiable: DoNotSchedule labelSelector: matchLabels: environment: production ``` The `DoNotSchedule` condition prevents labeled pods from being scheduled onto Kubernetes worker nodes when doing so would fail to meet the spread and topology constraints specified with `maxSkew` and `topologyKey`, respectively. For more context on how these rules work, see the [Kubernetes documentation](https://kubernetes.io/docs/concepts/workloads/pods/pod-topology-spread-constraints/). The [custom resource definition](https://github.com/cockroachdb/helm-charts/blob/master/cockroachdb-parent/charts/cockroachdb/values.yaml) details the fields supported by the operator. ## Resource labels and annotations To assist in working with your cluster, you can add labels and annotations to your resources. Specify labels in `cockroachdb.crdbCluster.podTemplate.metadata.labels` and annotations in `cockroachdb.crdbCluster.podTemplate.metadata.annotations` in the values file used to deploy the cluster: ```yaml theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} cockroachdb: crdbCluster: podTemplate: metadata: labels: app.kubernetes.io/name: "cockroachdb" annotations: kubernetes.io/description: "This is a CockroachDB pod." ``` To verify that the labels and annotations were applied to a pod, for example, run `kubectl describe pod {pod-name}`. For more information about [labels](https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/) and [annotations](https://kubernetes.io/docs/concepts/overview/working-with-objects/annotations/), see the Kubernetes documentation.