Kubernetes 1.25: PodHasNetwork Condition for Pods
Author: Deep Debroy (Apple)
Kubernetes 1.25 introduces Alpha support for a new kubelet-managed pod condition
in the status field of a pod:
PodHasNetwork. The kubelet, for a worker node,
will use the
PodHasNetwork condition to accurately surface the initialization
state of a pod from the perspective of pod sandbox creation and network
configuration by a container runtime (typically in coordination with CNI
plugins). The kubelet starts to pull container images and start individual
containers (including init containers) after the status of the
condition is set to
"True". Metrics collection services that report latency of
pod initialization from a cluster infrastructural perspective (i.e. agnostic of
per container characteristics like image size or payload) can utilize the
PodHasNetwork condition to accurately generate Service Level Indicators
(SLIs). Certain operators or controllers that manage underlying pods may utilize
PodHasNetwork condition to optimize the set of actions performed when pods
repeatedly fail to come up.
How is this different from the existing Initialized condition reported for pods?
The kubelet sets the status of the existing
Initialized condition reported in
the status field of a pod depending on the presence of init containers in a pod.
If a pod specifies init containers, the status of the
Initialized condition in
the pod status will not be set to
"True" until all init containers for the pod
have succeeded. However, init containers, configured by users, may have errors
(payload crashing, invalid image, etc) and the number of init containers
configured in a pod may vary across different workloads. Therefore,
cluster-wide, infrastructural SLIs around pod initialization cannot depend on
Initialized condition of pods.
If a pod does not specify init containers, the status of the
condition in the pod status is set to
"True" very early in the lifecycle of
the pod. This occurs before the kubelet initiates any pod runtime sandbox
creation and network configuration steps. As a result, a pod without init
containers will report the status of the
Initialized condition as
even if the container runtime is not able to successfully initialize the pod
Relative to either situation above, the
PodHasNetwork condition surfaces more
accurate data around when the pod runtime sandbox was initialized with
networking configured so that the kubelet can proceed to launch user-configured
containers (including init containers) in the pod.
If a pod specifies
PodHasNetwork condition is
"True" based on successful creation of the pod sandbox while the
network configuration state of the pod sandbox is ignored. This is because the
CRI implementation typically skips any pod sandbox network configuration when
hostNetwork is set to
"True" for a pod.
A node agent may dynamically re-configure network interface(s) for a pod by
watching changes in pod annotations that specify additional networking
k8s.v1.cni.cncf.io/networks). Dynamic updates of pod
networking configuration after the pod sandbox is initialized by Kubelet (in
coordination with a container runtime) are not reflected by the
Try out the PodHasNetwork condition for pods
In order to have the kubelet report the
PodHasNetwork condition in the status
field of a pod, please enable the
PodHasNetworkCondition feature gate on the
For a pod whose runtime sandbox has been successfully created and has networking
configured, the kubelet will report the
PodHasNetwork condition with status set to
$ kubectl describe pod nginx1 Name: nginx1 Namespace: default ... Conditions: Type Status PodHasNetwork True Initialized True Ready True ContainersReady True PodScheduled True
For a pod whose runtime sandbox has not been created yet (and networking not
configured either), the kubelet will report the
PodHasNetwork condition with
status set to
$ kubectl describe pod nginx2 Name: nginx2 Namespace: default ... Conditions: Type Status PodHasNetwork False Initialized True Ready False ContainersReady False PodScheduled True
Depending on feedback and adoption, the Kubernetes team plans to push the
reporting of the
PodHasNetwork condition to Beta in 1.26 or 1.27.
How can I learn more?
Please check out the
documentation for the
PodHasNetwork condition to learn more about it and how it fits in relation to
other pod conditions.
How to get involved?
This feature is driven by the SIG Node community. Please join us to connect with the community and share your ideas and feedback around the above feature and beyond. We look forward to hearing from you!
We want to thank the following people for their insightful and helpful reviews of the KEP and PRs around this feature: Derek Carr (@derekwaynecarr), Mrunal Patel (@mrunalp), Dawn Chen (@dchen1107), Qiutong Song (@qiutongs), Ruiwen Zhao (@ruiwen-zhao), Tim Bannister (@sftim), Danielle Lancashire (@endocrimes) and Agam Dua (@agamdua).