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KEP-3695: extend pod resource API to for DRA
Signed-off-by: Moshe Levi <moshele@nvidia.com>
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| # KEP-3695: Extend the PodResources API to include resources allocated by DRA | ||
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| <!-- toc --> | ||
| - [Release Signoff Checklist](#release-signoff-checklist) | ||
| - [Summary](#summary) | ||
| - [Motivation](#motivation) | ||
| - [Goals](#goals) | ||
| - [Non-Goals](#non-goals) | ||
| - [Proposal](#proposal) | ||
| - [Risks and Mitigations](#risks-and-mitigations) | ||
| - [Design Details](#design-details) | ||
| - [Proposed API](#proposed-api) | ||
| - [Unit tests](#unit-tests) | ||
| - [Integration tests](#integration-tests) | ||
| - [e2e tests](#e2e-tests) | ||
| - [Graduation Criteria](#graduation-criteria) | ||
| - [Alpha](#alpha) | ||
| - [Beta](#beta) | ||
| - [GA](#ga) | ||
| - [Upgrade / Downgrade Strategy](#upgrade--downgrade-strategy) | ||
| - [Version Skew Strategy](#version-skew-strategy) | ||
| - [Production Readiness Review Questionnaire](#production-readiness-review-questionnaire) | ||
| - [Feature Enablement and Rollback](#feature-enablement-and-rollback) | ||
| - [Rollout, Upgrade and Rollback Planning](#rollout-upgrade-and-rollback-planning) | ||
| - [Monitoring Requirements](#monitoring-requirements) | ||
| - [Dependencies](#dependencies) | ||
| - [Scalability](#scalability) | ||
| - [Troubleshooting](#troubleshooting) | ||
| - [Implementation History](#implementation-history) | ||
| - [Drawbacks](#drawbacks) | ||
| - [Alternatives](#alternatives) | ||
| <!-- /toc --> | ||
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| ## Release Signoff Checklist | ||
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| Items marked with (R) are required *prior to targeting to a milestone / release*. | ||
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| - [x] (R) Enhancement issue in release milestone, which links to KEP dir in [kubernetes/enhancements] (not the initial KEP PR) | ||
| - [ ] (R) KEP approvers have approved the KEP status as `implementable` | ||
| - [ ] (R) Design details are appropriately documented | ||
| - [ ] (R) Test plan is in place, giving consideration to SIG Architecture and SIG Testing input (including test refactors) | ||
| - [ ] e2e Tests for all Beta API Operations (endpoints) | ||
| - [ ] (R) Ensure GA e2e tests meet requirements for [Conformance Tests](https://github.com/kubernetes/community/blob/master/contributors/devel/sig-architecture/conformance-tests.md) | ||
| - [ ] (R) Minimum Two Week Window for GA e2e tests to prove flake free | ||
| - [ ] (R) Graduation criteria is in place | ||
| - [ ] (R) [all GA Endpoints](https://github.com/kubernetes/community/pull/1806) must be hit by [Conformance Tests](https://github.com/kubernetes/community/blob/master/contributors/devel/sig-architecture/conformance-tests.md) | ||
| - [ ] (R) Production readiness review completed | ||
| - [ ] (R) Production readiness review approved | ||
| - [ ] "Implementation History" section is up-to-date for milestone | ||
| - [ ] User-facing documentation has been created in [kubernetes/website], for publication to [kubernetes.io] | ||
| - [ ] Supporting documentation—e.g., additional design documents, links to mailing list discussions/SIG meetings, relevant PRs/issues, release notes | ||
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| <!-- | ||
| **Note:** This checklist is iterative and should be reviewed and updated every time this enhancement is being considered for a milestone. | ||
| --> | ||
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| [kubernetes.io]: https://kubernetes.io/ | ||
| [kubernetes/enhancements]: https://git.k8s.io/enhancements | ||
| [kubernetes/kubernetes]: https://git.k8s.io/kubernetes | ||
| [kubernetes/website]: https://git.k8s.io/website | ||
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| ## Summary | ||
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| We propose an enhancement to the pod resource api to include resources allocated by [Dynamic Resource Allocation (DRA)](https://github.com/kubernetes/enhancements/tree/master/keps/sig-node/3063-dynamic-resource-allocation). We also propose to extend the API to be more friendly for consumption by CNI meta-plugins. | ||
| This kep is extends [2043-pod-resource-concrete-assigments](https://github.com/kubernetes/enhancements/tree/master/keps/sig-node/2043-pod-resource-concrete-assigments) and [2403-pod-resources-allocatable-resources](https://github.com/kubernetes/enhancements/tree/master/keps/sig-node/2403-pod-resources-allocatable-resources). | ||
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| ## Motivation | ||
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| The pod resource API is currently being used by CNI meta-plugins like [multus](https://github.com/k8snetworkplumbingwg/multus-cni) and [DANM](https://github.com/nokia/danm) to add resources allocated by Device Plugin as CNI arguments. The motivation is to allow the API to be used for resources allocated by DRA. Additionally, the porposed API will make it easier for CNI meta-plugins to access the resources allocated to a specific pod, rather than having to filter through resources for all pods on the node. Another use-case is to allow node monitoring agents to access information about allocated resources. | ||
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| ### Goals | ||
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| Enabling the DRA feature to work with CNIs that require complex network devices such as RDMA. The DRA will allocate the resources, and the meta-plugin will read the allocated [CDI Device](https://github.com/container-orchestrated-devices/container-device-interface) using the Pod resource API. The meta-plugin will then inject the device-id as CNI arguments and invoke other CNIs. | ||
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| ### Non-Goals | ||
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| To enhance pod resource API GetAllocatableResources for resources that managed by DRA. With DRA there is not standard | ||
| way to get resource captivity. | ||
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| ## Proposal | ||
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| ### Risks and Mitigations | ||
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| This API is read-only, which removes a large class of risks. The aspects that we consider below are as follows: | ||
| - What are the risks associated with the API service itself? | ||
| - What are the risks associated with the data itself? | ||
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| | Risk | Impact | Mitigation | | ||
| | --------------------------------------------------------- | ------------- | ---------- | | ||
| | Too many requests risk impacting the kubelet performances | High | Implement rate limiting and or passive caching, follow best practices for gRPC resource management. | | ||
| | Improper access to the data | Low | Server is listening on a root owned unix socket. This can be limited with proper pod security policies. | | ||
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| ## Design Details | ||
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| ### Proposed API | ||
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| Our proposal is to extend the existing pod resources gRPC service of the Kubelet by adding the CDIDevices field to the ContainerResources message. This new field will contain information about the DRA driver name, the DRA resource class, and a list of CDI Devices allocated by that DRA driver. It's important to note that this proposal focuses on retrieving CDI devices allocated by DRA. Other mechanisms that may utilize CDI, such as device plugin, are not included in the scope of this proposal. | ||
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| Additionally, we propose adding a Get method to the existing gRPC service to allow querying specific pods for their allocated resources. | ||
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| The extended interface is shown in proto below: | ||
| ```protobuf | ||
| // PodResourcesLister is a service provided by the kubelet that provides information about the | ||
| // node resources consumed by pods and containers on the node | ||
| service PodResourcesLister { | ||
| rpc List(ListPodResourcesRequest) returns (ListPodResourcesResponse) {} | ||
| rpc GetAllocatableResources(AllocatableResourcesRequest) returns (AllocatableResourcesResponse) {} | ||
| rpc Get(GetPodResourcesRequest) returns (GetPodResourcesResponse) {} | ||
| } | ||
| message AllocatableResourcesRequest {} | ||
| // AllocatableResourcesResponses contains informations about all the devices known by the kubelet | ||
| message AllocatableResourcesResponse { | ||
| repeated ContainerDevices devices = 1; | ||
| repeated int64 cpu_ids = 2; | ||
| repeated ContainerMemory memory = 3; | ||
| } | ||
| // ListPodResourcesRequest is the request made to the PodResourcesLister service | ||
| message ListPodResourcesRequest {} | ||
| // ListPodResourcesResponse is the response returned by List function | ||
| message ListPodResourcesResponse { | ||
| repeated PodResources pod_resources = 1; | ||
| } | ||
| // PodResources contains information about the node resources assigned to a pod | ||
| message PodResources { | ||
| string name = 1; | ||
| string namespace = 2; | ||
| repeated ContainerResources containers = 3; | ||
| } | ||
| // ContainerResources contains information about the resources assigned to a container | ||
| message ContainerResources { | ||
| string name = 1; | ||
| repeated ContainerDevices devices = 2; | ||
| repeated int64 cpu_ids = 3; | ||
| repeated ContainerMemory memory = 4; | ||
| repeated CDIDevices cdi_devices = 5; | ||
| } | ||
| // ContainerMemory contains information about memory and hugepages assigned to a container | ||
| message ContainerMemory { | ||
| string memory_type = 1; | ||
| uint64 size = 2; | ||
| TopologyInfo topology = 3; | ||
| } | ||
| // ContainerDevices contains information about the devices assigned to a container by device plugin | ||
| message ContainerDevices { | ||
| string resource_name = 1; | ||
| repeated string device_ids = 2; | ||
| TopologyInfo topology = 3; | ||
| } | ||
| // Topology describes hardware topology of the resource | ||
| message TopologyInfo { | ||
| repeated NUMANode nodes = 1; | ||
| } | ||
| // NUMA representation of NUMA node | ||
| message NUMANode { | ||
| int64 ID = 1; | ||
| } | ||
| // CDIDevices contains information about the devices assigned to a container by DRA | ||
| message CDIDevices { | ||
| string driver_name = 1; | ||
| string resource_class = 2; | ||
| repeated string device_ids = 1; | ||
| } | ||
| // GetPodResourcesRequest contains information about the pod | ||
| message GetPodResourcesRequest { | ||
| string name = 1; | ||
| string namespace = 2; | ||
| } | ||
| // GetPodResourcesResponse contains information about the pod the devices | ||
| message GetPodResourcesResponse { | ||
| PodResources pod_resources = 1; | ||
| } | ||
| ``` | ||
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| ##### Unit tests | ||
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| - `k8s.io/kubernetes/pkg/kubelet/apis/podresources`: `12-14-2022` - @TODO how to get coverage number? | ||
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| ##### Integration tests | ||
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| These cases will be added in the existing integration tests: | ||
| - Feature gate enable/disable tests. | ||
| - Get API work with DRA and device plugin. | ||
| - List API work with DRA and Device plugin. | ||
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| ##### e2e tests | ||
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| These cases will be added in the existing e2e tests: | ||
| - Feature gate enable/disable tests. | ||
| - Get API work with DRA and device plugin. | ||
| - List API work with DRA and Device plugin. | ||
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| ### Graduation Criteria | ||
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| #### Alpha | ||
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| - [X] Feature implemented behind a feature flag. | ||
| - [X] e2e tests completed and enabled. | ||
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| #### Beta | ||
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| - [ ] Gather feedback from consumers of the DRA feature and k8snetworkplumbingwg working group | ||
| - [ ] No major bugs reported in the previous cycle. | ||
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| #### GA | ||
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| - [ ] Allowing time for feedback (1 year). | ||
| - [ ] Risks have been addressed. | ||
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| ### Upgrade / Downgrade Strategy | ||
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| With gRPC the version is part of the service name. | ||
| Old versions and new versions should always be served and listened by the kubelet. | ||
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| To a cluster admin upgrading to the newest API version, means upgrading Kubernetes to a newer version as well as upgrading the monitoring component. | ||
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| To a vendor changes in the API should always be backwards compatible. | ||
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| ### Version Skew Strategy | ||
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| Kubelet will always be backwards compatible, so going forward existing plugins are not expected to break. | ||
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| ## Production Readiness Review Questionnaire | ||
| ### Feature Enablement and Rollback | ||
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| ###### How can this feature be enabled / disabled in a live cluster? | ||
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| - [x] Feature gate (also fill in values in `kep.yaml`) | ||
| - Feature gate name: PodResourcesCDIDevices. | ||
| - Components depending on the feature gate: kubelet, 3rd party consumers. | ||
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| ###### Does enabling the feature change any default behavior? | ||
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| No. | ||
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| ###### Can the feature be disabled once it has been enabled (i.e. can we roll back the enablement)? | ||
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| Yes, through feature gates. | ||
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| ###### What happens if we reenable the feature if it was previously rolled back? | ||
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| The API becomes available again. The API is stateless, so no recovery is needed, clients can just consume the data. | ||
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| ###### Are there any tests for feature enablement/disablement? | ||
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| e2e test will demonstrate that when the feature gate is disabled, the API returns the appropriate error code. | ||
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| ### Rollout, Upgrade and Rollback Planning | ||
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| ###### How can a rollout or rollback fail? Can it impact already running workloads? | ||
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| Kubelet may fail to start. The new API may report inconsistent data, or may cause the kubelet to crash. | ||
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| ###### What specific metrics should inform a rollback? | ||
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| `pod_resources_endpoint_errors_get` - but only with feature gate enabled. Otherwise the API will always return a known error, giving a false negative signal. | ||
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| ###### Were upgrade and rollback tested? Was the upgrade->downgrade->upgrade path tested? | ||
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| Not Applicable. | ||
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| ###### Is the rollout accompanied by any deprecations and/or removals of features, APIs, fields of API types, flags, etc.? | ||
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| No. | ||
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| ### Monitoring Requirements | ||
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| ###### How can an operator determine if the feature is in use by workloads? | ||
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| Look at the `pod_resources_endpoint_requests_listi` and `pod_resources_endpoint_requests_get` metric exposed by the kubelet. | ||
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| ###### How can someone using this feature know that it is working for their instance? | ||
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| <!-- | ||
| For instance, if this is a pod-related feature, it should be possible to determine if the feature is functioning properly | ||
| for each individual pod. | ||
| Pick one more of these and delete the rest. | ||
| Please describe all items visible to end users below with sufficient detail so that they can verify correct enablement | ||
| and operation of this feature. | ||
| Recall that end users cannot usually observe component logs or access metrics. | ||
| --> | ||
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| - [ ] Events | ||
| - Event Reason: | ||
| - [ ] API .status | ||
| - Condition name: | ||
| - Other field: | ||
| - [ ] Other (treat as last resort) | ||
| - Details: | ||
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| ###### What are the reasonable SLOs (Service Level Objectives) for the enhancement? | ||
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| N/A. | ||
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| ###### What are the SLIs (Service Level Indicators) an operator can use to determine the health of the service? | ||
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| - [X ] Metrics | ||
| - Metric name: `pod_resources_endpoint_requests_total`, `pod_resources_endpoint_requests_list | ||
| - Components exposing the metric: kubelet | ||
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| ###### Are there any missing metrics that would be useful to have to improve observability of this feature? | ||
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| As part of this feature enhancement, per-API-endpoint resources metrics are being added; to observe this feature the `pod_resources_endpoint_requests_get` and `pod_resources_endpoint_requests_list` metric should be used. We will add `pod_resources_endpoint_errors_get` error counter. | ||
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| ### Dependencies | ||
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| ###### Does this feature depend on any specific services running in the cluster? | ||
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| No. | ||
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| ### Scalability | ||
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| ###### Will enabling / using this feature result in any new API calls? | ||
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| No. | ||
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| ###### Will enabling / using this feature result in introducing new API types? | ||
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| No. | ||
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| ###### Will enabling / using this feature result in any new calls to the cloud provider? | ||
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| No. | ||
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| ###### Will enabling / using this feature result in increasing size or count of the existing API objects? | ||
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| No. | ||
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| ###### Will enabling / using this feature result in increasing time taken by any operations covered by existing SLIs/SLOs? | ||
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| No. Feature is out of existing any paths in kubelet. | ||
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| ###### Will enabling / using this feature result in non-negligible increase of resource usage (CPU, RAM, disk, IO, ...) in any components? | ||
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| DDOSing the API can lead to resource exhaustion. | ||
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| ### Troubleshooting | ||
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| ###### How does this feature react if the API server and/or etcd is unavailable? | ||
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| N/A. | ||
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| ###### What are other known failure modes? | ||
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| the API will always return a well-known error. In normal operation, the API is expected to never return error and always return a valid response, because it utilizes internal kubelet data which is always available. Bugs may lead to the API to return unexpected errors, or to return inconsistent data. Consumers of the API should treat unexpected errors as bugs of this API. | ||
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| ###### What steps should be taken if SLOs are not being met to determine the problem? | ||
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| N/A. | ||
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| ## Implementation History | ||
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| - 2023-01-12: KEP created | ||
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| ## Drawbacks | ||
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| ## Alternatives |
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