Rancher Agents
There are two different agent resources deployed on Rancher managed clusters:
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.
cattle-node-agent
The cattle-node-agent
is used to interact with nodes in a Rancher Launched Kubernetes cluster when performing cluster operations. Examples of cluster operations are upgrading Kubernetes version and creating/restoring etcd snapshots. The cattle-node-agent
is deployed using a DaemonSet resource to make sure it runs on every node. The cattle-node-agent
is used as fallback option to connect to the Kubernetes API of Rancher Launched Kubernetes clusters when cattle-cluster-agent
is unavailable.
Note: In Rancher v2.2.4 and lower, the
cattle-node-agent
pods did not tolerate all taints, causing Kubernetes upgrades to fail on these nodes. The fix for this has been included in Rancher v2.2.5 and higher.
Scheduling rules
Applies to v2.3.0 up to v2.5.3
Component | nodeAffinity nodeSelectorTerms | nodeSelector | Tolerations |
---|---|---|---|
cattle-cluster-agent | beta.kubernetes.io/os:NotIn:windows | none | operator:Exists |
cattle-node-agent | beta.kubernetes.io/os:NotIn:windows | none | operator:Exists |
The cattle-cluster-agent
Deployment has preferred scheduling rules using preferredDuringSchedulingIgnoredDuringExecution
, favoring to be scheduled on nodes with the controlplane
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" |
1 | node-role.kubernetes.io/etcd:In:"true" |