As davidopp@ mentioned a pod is the unit of scheduling. So to find a suitable node for a pod, the scheduler has to identify a node that sum(all container requests) available.
It is also used by the node to enforce overall resource usage across all containers. Not all memory is reclaimed when a container dies or restarts and so we need an isolation sandbox that spans across all the containers. It's not a "concept", but more of an implementation detail. Maybe we can clarify that more explicitly until we introduce it as a concept in the future? On Fri, May 5, 2017 at 12:35 AM, 'David Oppenheimer' via Kubernetes user discussion and Q&A <kubernetes-users@googlegroups.com> wrote: > > > On Wed, May 3, 2017 at 12:10 PM, 'Ahmet Alp Balkan' via Kubernetes user > discussion and Q&A <kubernetes-users@googlegroups.com> wrote: > >> I am afraid it still does not make sense to me. >> >> Why is there even a concept of "Pod-level request/limit" if it is not >> used anywhere? >> > > It is used by the scheduler. Pod is the atomic unit of scheduling. > > >> As a user, this is confusing me. As far as I can tell, I can configure >> limits on the Container and if I go beyond that my *Pod* will be killed >> altogether. This part is clear. However I can't tell what a Pod-level >> request/limit (just a sum of things which I can't configure directly) does >> on my cluster today? >> >> On Wed, May 3, 2017 at 11:30 AM, 'David Oppenheimer' via Kubernetes user >> discussion and Q&A <kubernetes-users@googlegroups.com> wrote: >> >>> >>> >>> On Wed, May 3, 2017 at 10:47 AM, 'Ahmet Alp Balkan' via Kubernetes user >>> discussion and Q&A <kubernetes-users@googlegroups.com> wrote: >>> >>>> Hello, I am trying to understand the Resource Limits/Requests for Pods >>>> and Containers >>>> <https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/> >>>> document. >>>> In multiple places, the document implies that users can specify >>>> ResourceRequirements *at pod-level**. *(I don't mean >>>> pod.spec.containers.resources.) Most relevantly the doc says: >>>> >>>> A Pod resource request/limit for a particular resource type* is the >>>>> sum *of the resource requests/limits of that type for each Container >>>>> in the Pod. >>>> >>>> >>> Request and limit are specified only at the per-container level. The >>> system computes pod-level request and limit by adding up the request and >>> limit of the containers that are inside the pod. But you can't specify it >>> at the pod level yourself. >>> >>> Does that make sense? >>> >>> >>> >>>> >>>> However I can’t find any examples or any fields on the API (kubectl >>>> explain pod.spec) to specify resource requirements on the pod level. >>>> >>>> Any ideas if this is possible at all? This particular document is >>>> particularly gives the strong impression that this feature exists today. I >>>> opened this docs issue >>>> <https://github.com/kubernetes/kubernetes.github.io/issues/3608> to >>>> track this. >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "Kubernetes user discussion and Q&A" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to kubernetes-users+unsubscr...@googlegroups.com. >>>> To post to this group, send email to kubernetes-users@googlegroups.com. >>>> Visit this group at https://groups.google.com/group/kubernetes-users. >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Kubernetes user discussion and Q&A" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to kubernetes-users+unsubscr...@googlegroups.com. >>> To post to this group, send email to kubernetes-users@googlegroups.com. >>> Visit this group at https://groups.google.com/group/kubernetes-users. >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Kubernetes user discussion and Q&A" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to kubernetes-users+unsubscr...@googlegroups.com. >> To post to this group, send email to kubernetes-users@googlegroups.com. >> Visit this group at https://groups.google.com/group/kubernetes-users. >> For more options, visit https://groups.google.com/d/optout. >> > > -- > You received this message because you are subscribed to the Google Groups > "Kubernetes user discussion and Q&A" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to kubernetes-users+unsubscr...@googlegroups.com. > To post to this group, send email to kubernetes-users@googlegroups.com. > Visit this group at https://groups.google.com/group/kubernetes-users. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Kubernetes user discussion and Q&A" group. 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