OpenShift DaemonSet Operations

External

• https://docs.openshift.com/container-platform/3.5/dev_guide/daemonsets.html

Internal

• OpenShift Operations
• OpenShift Concepts - DaemonSets

Obtaining Information about DaemonSets

The name of the DaemonSet that manages a pod is available in pod's "oc describe pod" output, as value for the "Controllers:" label. That value can be used to get the DaemonSet definition:

 oc describe DaemonSet/<daemon-set-name>

Example:

 oc describe DaemonSet/logging-fluentd

Name:		logging-fluentd
Image(s):	registry.access.redhat.com/openshift3/logging-fluentd:3.5.0
Selector:	component=fluentd,provider=openshift
Node-Selector:	logging-infra-fluentd=true
Labels:		component=fluentd
		logging-infra=fluentd
		provider=openshift
Desired Number of Nodes Scheduled: 7
Current Number of Nodes Scheduled: 7
Number of Nodes Misscheduled: 0
Pods Status:	2 Running / 0 Waiting / 0 Succeeded / 5 Failed
No events.

Creating Daemon Sets

TODO: https://docs.openshift.com/container-platform/3.5/dev_guide/daemonsets.html#dev-guide-creating-daemonsets

Updating Pods Managed by DaemonSets

As long as a pod managed by a DaemonSet is running, it is impervious to changes in its own template: the DaemonSet won't react and attempt to stop it and recreate it. This behavior is consistent with the static nature of running pods. Moreover, if the definition of a DaemonSet-managed pod is completely deleted, and then recreated based on a new template, but the same label selector, the DaemonSet will recognize any running pod replicas as having matching labels and thus will not update them or create new replicas despite a mismatch in the pod template.

To update the pods managed by a DaemonSet, update the pod's template, and force new pod replica creation by deleting the existing replicas.

Updating the DaemonSet Definition

oc edit daemonset/<daemon-set-name>

Procedure

1. Update the DaemonSet definition, if needed.

2. Update the pod definition, if needed.

3. Delete the existing pods, they will be recreated by the DaemonSet:

 oc delete pod/logging-fluentd-3kz30
 oc delete pod/logging-fluentd-d150b
 ...