feat: add CustomResourceMonitor CRD (WIP) #2049
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| # Kube-State-Metrics - CustomResourceMonitor CRD Proposal | ||
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| Authors: Catherine Fang (CatherineF-dev@), Christian Schlotter (chrischdi@) | ||
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| Date: 26. Jun 2023 | ||
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| Target release: v | ||
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| --- | ||
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| ## Table of Contents | ||
| - [Glossary](#glossary) | ||
| - [Problem Statement](#problem-statement) | ||
| - [Goal](#goal) | ||
| - [Status Quo](#status-quo) | ||
| - [Proposal](#proposal) | ||
| - [New flags](#new-flags) | ||
| - [CustomResourceMonitor Definition](#customresourcemonitor-definition) | ||
| - [Watch and Reconcile on CustomResourceMonitor CRs](#watch-and-reconcile-on-customresourcemonitor-crs) | ||
| - [CUJ](#cuj) | ||
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| ## Glossary | ||
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| - kube-state-metrics: “Simple service that listens to the Kubernetes API server | ||
| and generates metrics about the state of the objects” | ||
| - Custom Resource: https://kubernetes.io/docs/concepts/extend-kubernetes/api-extension/custom-resources | ||
| - [CustomResourceState](https://github.com/kubernetes/kube-state-metrics/blob/main/docs/customresourcestate-metrics.md) monitoring feature: existing feature which collects custom resource metrics | ||
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| ## Problem Statement | ||
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| 1. Using CustomResourceState monitoring feature is not user-friendly. Current ways on configuring CustomResourceState monitoring are: | ||
| * `--custom-resource-state-config "inline yaml (see example)"` or | ||
| * `--custom-resource-state-config-file /path/to/config.yaml`. Either mounted or configmap. | ||
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| 2. Current CustomResourceState monitoring feature doesn't support multiple configuration files. | ||
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| For example, for a company with 10 teams, each team wants to collect Custom Resource metrics for their owned Custom Resources. | ||
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| ## Goal | ||
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| A better UX to collect custom resource metrics | ||
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| ## Proposal | ||
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| Add a custom resource definition (CustomResourceMonitor) which contains customresourcestate.Metrics. | ||
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| kube-state-metrics watched on CustomResourceMonitor CRs and concatenate these CRs into one config `customresourcestate.Metrics` which has the same content using `--custom-resource-state-config`. | ||
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| ### New flags | ||
| Apart from existing two flags (`--custom-resource-state-config ` and `--custom-resource-state-config-file`), these three flags will be added: | ||
| * `--custom_resource_monitor`: whether watch CustomResourceMonitor CRs or not. | ||
| * `--custom_resource_monitor_labels`: only watch CustomResourceMonitor with [labelSelectors](https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#list-and-watch-filtering). For example, `environment=production,tier=frontend` means selecting CustomResourceMonitor CRs which have these two labels. It's used to avoid double custom metrics collection when multiple kube-state-metrics are installed. | ||
| * `--custom_resource_monitor_namespaces`: only watch CustomResourceMonitor under namespaces=x. | ||
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| If `--custom_resources_monitor_enabled` is set, `--custom-resource-state-config` and `--custom-resource-state-config-file` will be ignored. | ||
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There was a problem hiding this comment. Is there a need to make it mutually exclusive? There was a problem hiding this comment. To simplify UX. The migration from |
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| ### CustomResourceMonitor Definition | ||
CatherineF-dev marked this conversation as resolved.
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| * GroupName: kubestatemetrics.io | ||
| * Alternative kubestatemetrics.k8s.io: 1. *.k8s.io needs approval 2. ksm isn't inside k/k repo (need to double confirm) | ||
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There was a problem hiding this comment. Do you know if this really needs approval and by whom? autoscaler also uses *.k8s.io: https://github.com/kubernetes/autoscaler/blob/master/vertical-pod-autoscaler/examples/hamster.yaml#L8 I would prefer using ksm.k8s.io or kubestatemetris.k8s.io |
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| * Alternative ksm.io: has been used by a company | ||
| * Version: v1alpha1 | ||
| * Kind: CustomResourceMonitor | ||
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| ```go | ||
| package v1alpha1 | ||
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| import ( | ||
| "k8s.io/kube-state-metrics/v2/pkg/customresourcestate" | ||
| ) | ||
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| type CustomResourceMonitor struct { | ||
| metav1.TypeMeta `json:",inline"` | ||
| metav1.ObjectMeta `json:"metadata,omitempty"` | ||
| customresourcestate.Metrics `json:",inline"` | ||
| } | ||
| ``` | ||
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| ```yaml | ||
| # Example CR | ||
| apiVersion: kubestatemetrics.io/v1alpha1 | ||
| kind: CustomResourceMonitor | ||
| metadata: | ||
| name: test-cr2 | ||
| namespace: kube-system | ||
| generation: 1 | ||
| spec: | ||
| resources: | ||
| - groupVersionKind: | ||
| group: myteam.io | ||
| kind: "Foo" | ||
| version: "v1" | ||
| metrics: | ||
| - name: "uptime" | ||
| help: "Foo uptime" | ||
| each: | ||
| type: Gauge | ||
| gauge: | ||
| path: [status, uptime] | ||
| ``` | ||
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| ### Watch and Reconcile on CustomResourceMonitor CRs | ||
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| Kube-state-metrics listens on add, update and delete events of CustomResourceMonitor via Kubernetes | ||
| client-go reflectors. On these events kube-state-metrics lists all CustomResourceMonitor CRs and concatenate CRs into one config `customresourcestate.Metrics` which has the almost same content with `--custom-resource-state-config` config. | ||
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| This generated custom resource config updates CustomResourceStore by adding monitored custom resource stores and deleting unmonitored custom resource stores. | ||
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| ```yaml | ||
| # example cr | ||
| apiVersion: kubestatemetrics.io/v1alpha1 | ||
| kind: CustomResourceMonitor | ||
| metadata: | ||
| name: nodepool | ||
| spec: | ||
| resources: | ||
| - groupVersionKind: | ||
| group: addons.k8s.io | ||
| kind: "FakedNodePool" | ||
| version: "v1alpha1" | ||
| metrics: | ||
| - name: "nodepool_generation" | ||
| help: "Nodepool generation" | ||
| each: | ||
| type: Gauge | ||
| gauge: | ||
| path: [metadata, generation] | ||
| ``` | ||
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| ``` | ||
| +---------------+ +---------------------+ +-----------------------+ | ||
| | CRM_informer | | nodepool_reflector | | custom_resource_store | | ||
| +---------------+ +---------------------+ +-----------------------+ | ||
| ---------------------\ | | | | ||
| | add/update/delete |-| | | | ||
| | CustomResource | | | | | ||
| | Monitor CR | | | | | ||
| | (monitor-nodepool) | | | | | ||
| |--------------------| | | | | ||
| | | | | ||
| | ListAndAddCustomResourceMonitors() | | ||
| |-------------------------------------------------->| | ||
| | | | | ||
| | DeleteOldCustomResourceMonitors() | | ||
| |-------------------------------------------------->| | ||
| | | | | ||
| | | Update(nodepool) | | ||
| | |----------------------------->| | ||
| | | | ----------\ | ||
| | | |-| Build() | | ||
| | | | |---------| | ||
| | | | ----------------------------\ | ||
| | | |-| generateMetrics(nodepool) | | ||
| | | | |---------------------------| | ||
| | | | | ||
| ``` | ||
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| <details> | ||
| <summary>Code to reproduce diagram</summary> | ||
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| Build via [text-diagram](http://weidagang.github.io/text-diagram/) | ||
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| ``` | ||
| object CRM_informer nodepool_reflector custom_resource_store | ||
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| note left of CRM_informer: add/update/delete \n CustomResource \n Monitor CR \n(monitor-nodepool) | ||
| CRM_informer -> custom_resource_store: ListAndAddCustomResourceMonitors() | ||
| CRM_informer -> custom_resource_store: DeleteOldCustomResourceMonitors() | ||
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| nodepool_reflector -> custom_resource_store: Update(nodepool) | ||
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| note right of custom_resource_store: Build() | ||
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| note right of custom_resource_store: generateMetrics(nodepool) | ||
| ``` | ||
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| </details> | ||
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| Custom Resource store always [adds](https://github.com/kubernetes/kube-state-metrics/blob/main/internal/store/builder.go#L186) new custom resource metrics. Deletion of custom resource metrics needs to be implemented. | ||
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| ### Alternatives | ||
| - Generate metrics configuration based on field annotations: https://github.com/kubernetes/kube-state-metrics/issues/1899 | ||
| - Limitation: need to have source code permission | ||
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| ## Migrate from CustomResourceState | ||
| ``` | ||
| + apiVersion: kubestatemetrics.io/v1alpha1 | ||
| - kind: CustomResourceStateMetrics | ||
| + kind: CustomResourceMonitor | ||
| + metadata: | ||
| + name: crm_nodepool | ||
| + labels: | ||
| + monitoring.backend.io: true | ||
| spec: # copy content from --custom-resource-state-config-file | ||
| ``` | ||
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| ## Critical User Journey (CUJ) | ||
| * cloud-provider: watch CustomResourceMonitor CRs with label `monitoring.(gke|aks|eks).io=true` under system namespaces | ||
| * application platform: watch CustomResourceMonitor CRs with label `monitoring.frontend.io=true` under non-system namespaces | ||
| * monitoring platform team: watch CustomResourceMonitor CRs with label `monitoring.platform.io=true` under non-system namespaces | ||
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| # TODO: use another CR | ||
| apiVersion: customresource.ksm.io/v1alpha1 | ||
| kind: CustomResourceMonitor | ||
| metadata: | ||
| name: test-cr | ||
| namespace: kube-system | ||
| generation: 2 | ||
| spec: | ||
| resources: | ||
| - groupVersionKind: | ||
| group: addons.gke.io | ||
| kind: "Stackdriver" | ||
| version: "v1alpha1" | ||
| metrics: | ||
| - name: "uptime" | ||
| help: "Foo uptime" | ||
| each: | ||
| type: Gauge | ||
| gauge: | ||
| path: [metadata, generation] |
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| apiVersion: customresource.ksm.io/v1alpha1 | ||
| kind: CustomResourceMonitor | ||
| metadata: | ||
| name: test-cr2 | ||
| namespace: kube-system | ||
| generation: 1 | ||
| spec: | ||
| resources: | ||
| - groupVersionKind: | ||
| group: customresource.ksm.io | ||
| kind: "CustomResourceMonitor" | ||
| version: "v1alpha1" | ||
| metrics: | ||
| - name: "uptime2" | ||
| help: "Bar uptime" | ||
| each: | ||
| type: Gauge | ||
| gauge: | ||
| path: [metadata, generation] |
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Should we consider a denylist for namespaces as well?
In case someone has a "platform KSM" (only selected namespaces) and a "product KSM" (everything else)?