Commits on Oct 6, 2020

1. Add numaid and cpus into PodResources interface …

   This change necessary for resource with topology exporting daemon,
   which used in topology aware scheduling.
   
   Information about CPU is keeping in cpu_ids, since it's  enough to
   represent both quantity and numaid. NUMAid can be obtained from
   cadvisor MachineInfo, since id in cpus_ids is a thread_id.
   This API doesn't provide cpu fraction, since it could be obtainded from
   Pod's request/limits and in case of non-integer CPU quantity and
   non-guaranteed QoS cpu assigned is not exclusive and NUMA id is not
   interesting.
   
   Device assignment on the NUMA node is representing by Topology
   structure. The structure was chosen because of several reason:
    more extensibility (with keeping backward compatibility)
    more compact representation of case when we have device aligned on
   several NUMA nodes (compared to just numa_id field in ContainerDevices)
   
   Signed-off-by: Alexey Perevalov <alexey.perevalov@huawei.com>

   

   AlexeyPerevalov committed Oct 6, 2020
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2. podresources: add endpoint to query all resources …

   To enable topology aware scheduling, the reporting agent wants
   to learn about the available resources on the worker node, in
   order to then let the scheduler know and do an informed decision.
   
   As it is now, the kubelet is the only authoritative source for
   the resource accounting, for example because it manages the devices
   plugin. Thus we need to extract this information from the kubelet.
   
   A good fit for this task is the podresources API, and we add here
   a new endpoint to let clients enumerate the resources.
   
   Signed-off-by: Francesco Romani <fromani@redhat.com>

   

   ffromani authored and AlexeyPerevalov committed Oct 6, 2020
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3. node: podresources: address review comments …

   Signed-off-by: Francesco Romani <fromani@redhat.com>
   Signed-off-by: Alexey Perevalov <alexey.perevalov@huawei.com>

   

   ffromani authored and AlexeyPerevalov committed Oct 6, 2020
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4. podresources: add Watch API …

   Extend the protocol with a simple implementation of ListAndWatch
   to enable monitoring agents to be notified of resource allocation
   changes.
   
   A separate Watch endpoint presents the issue of
   enabling client applications to not lose any updates
   when both APIs are used.
   
   The straightforward option is to follow the generic k8s approach (see
   link below) and let kubelet keep a historical window of
   the last recent changes, so client applications have the chance to
   issue `List` and shortly after `Watch`, starting from the
   resourceVersion returned in `List`.
   The underlying assumption is indeed that `Watch` happens "shortly" after `List`,
   otherwise the system cannot guarantee the lack of gaps.
   
   However implementing this support requires to keep the aforementioned
   sliding window of changes, which however requires careful implementation
   to address scalability and safety guarantees.
   
   However, the `podresources` API is a specific API, so, while is good to
   follow as much as possible the generic API concepts, it also allows some
   possible little differences which can help keep the implementation
   simple and safe.
   
   This patch proposes a simplest possible approach to reconcile the
   `List` and `Watch` responses, providing the `resource_version` field and
   suggesting a little change in the client applications programming model.
   
   Inspired by the concepts found on
   https://kubernetes.io/docs/reference/using-api/api-concepts/#efficient-detection-of-changes
   
   Signed-off-by: Francesco Romani <fromani@redhat.com>

   

   ffromani authored and AlexeyPerevalov committed Oct 6, 2020
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5. podresources: fix markdown …

   align section with TOC
   
   Signed-off-by: Francesco Romani <fromani@redhat.com>

   

   ffromani authored and AlexeyPerevalov committed Oct 6, 2020
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6. address review comments …

   Signed-off-by: Francesco Romani <fromani@redhat.com>

   

   ffromani authored and AlexeyPerevalov committed Oct 6, 2020
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