Rancher Agents

There are two different agent resources deployed on Rancher managed clusters:

• cattle-cluster-agent
• rancher-system-agent

For a conceptual overview of how the Rancher server provisions clusters and communicates with them, refer to the architecture.

cattle-cluster-agent

The cattle-cluster-agent is used to connect to the Kubernetes API of Rancher Launched Kubernetes clusters. The cattle-cluster-agent is deployed using a Deployment resource.

rancher-system-agent

The rancher-system-agent is a daemon used to manage nodes in a Rancher provisioned RKE2/K3s Kubernetes cluster when performing cluster lifecycle operations. Examples of cluster operations include upgrading the Kubernetes version and creating/restoring etcd snapshots. The rancher-system-agent is designed to apply plans to the Rancher system and can support both local and remote plans.

Requests

The cattle-cluster-agent pod does not define the default CPU and memory request values. As a baseline, we recommend setting the CPU request at 50m and memory request at 100Mi. However, it is important that you assess your use case appropriately and that you allocate the correct resources to your cluster for your needs.

To configure request values through the UI:

1. When you create or edit an existing cluster, go to the Cluster Configuration.
2. Select the Cluster Agent subsection.
3. Configure your request values using the CPU Reservation and Memory Reservation fields as needed.

If you prefer to configure via YAML, add the following snippet to your configuration file:

spec:
  clusterAgentDeploymentCustomization:
    overrideResourceRequirements:
      requests:
        cpu: 50m
        memory: 100Mi 

Scheduling rules

The cattle-cluster-agent uses either a fixed set of tolerations, or dynamically-added tolerations based on taints applied to the control plane nodes. This structure allows Taint based Evictions to work properly for cattle-cluster-agent.

If control plane nodes are present in the cluster, the default tolerations will be replaced with tolerations matching the taints on the control plane nodes. The default set of tolerations are described below.

Component	nodeAffinity nodeSelectorTerms	nodeSelector	Tolerations
cattle-cluster-agent	beta.kubernetes.io/os:NotIn:windows	none	Note: These are the default tolerations, and will be replaced by tolerations matching taints applied to controlplane nodes. effect:NoSchedule key:node-role.kubernetes.io/controlplane value:true effect:NoSchedule key:node-role.kubernetes.io/control-plane operator:Exists effect:NoSchedule key:node-role.kubernetes.io/master operator:Exists

The cattle-cluster-agent Deployment has preferred scheduling rules using preferredDuringSchedulingIgnoredDuringExecution, favoring to be scheduled on nodes with the controlplane node. When there are no controlplane nodes visible in the cluster (this is usually the case when using Clusters from Hosted Kubernetes Providers), you can add the label cattle.io/cluster-agent=true on a node to prefer scheduling the cattle-cluster-agent pod to that node.

See Kubernetes: Assigning Pods to Nodes to find more information about scheduling rules.

The preferredDuringSchedulingIgnoredDuringExecution configuration is shown in the table below:

Weight	Expression
100	node-role.kubernetes.io/controlplane:In:"true"
100	node-role.kubernetes.io/control-plane:In:"true"
100	node-role.kubernetes.io/master:In:"true"
1	cattle.io/cluster-agent:In:"true"