kube-state-metrics

Overview

kube-state-metrics is a simple service that listens to the Kubernetes API server and generates metrics about the state of the objects. (See examples in the Metrics section below.) It is not focused on the health of the individual Kubernetes components, but rather on the health of the various objects inside, such as deployments, nodes and pods.

That kube-state-metrics is about generating metrics from Kubernetes API objects without modification. This ensures, that features provided by kube-state-metrics have the same grade of stability as the Kubernetes API objects themselves. In turn this means, that kube-state-metrics in certain situation may not show the exact same values as kubectl, as kubectl applies certain heuristics to display comprehensible messages. kube-state-metrics exposes raw data unmodified from the Kubernetes API, this way users have all the data they require and perform heuristics as they see fit.

The metrics are exported on the HTTP endpoint /metrics on the listening port (default 80). They are served as plaintext. They are designed to be consumed either by Prometheus itself or by a scraper that is compatible with scraping a Prometheus client endpoint. You can also open /metrics in a browser to see the raw metrics.

Table of Contents

• Versioning
  • Kubernetes Version
  • Compatibility matrix
  • Resource group version compatibility
  • Container Image
• Metrics Documentation
• Kube-state-metrics self metrics
• Resource recommendation
• kube-state-metrics vs. metrics-server(Heapster)
• Setup
  • Building the Docker container
• Usage
  • Kubernetes Deployment
  • Development

Versioning

Kubernetes Version

kube-state-metrics uses client-go to talk with Kubernetes clusters. The supported Kubernetes cluster version is determined by client-go. The compatibility matrix for client-go and Kubernetes cluster can be found here. All additional compatibility is only best effort, or happens to still/already be supported.

Compatibility matrix

At most 5 kube-state-metrics releases will be recorded below.

• ✓ Fully supported version range.
• - The Kubernetes cluster has features the client-go library can't use (additional API objects, etc).

Resource group version compatibility

Resources in Kubernetes can evolve, i.e., the group version for a resource may change from alpha to beta and finally GA in different Kubernetes versions. As for now, kube-state-metrics will only use the oldest API available in the latest release.

Container Image

The latest container image can be found at:

• quay.io/coreos/kube-state-metrics:v1.5.0
• k8s.gcr.io/kube-state-metrics:v1.5.0

Note: The recommended docker registry for kube-state-metrics is quay.io. kube-state-metrics on gcr.io is only maintained on best effort as it requires external help from Google employees.

Metrics Documentation

There are many more metrics we could report, but this first pass is focused on those that could be used for actionable alerts. Please contribute PR's for additional metrics!

WARNING: THESE METRIC/TAG NAMES ARE UNSTABLE AND MAY CHANGE IN A FUTURE RELEASE. For now the following metrics and collectors

metrics

• kube_pod_container_resource_requests_nvidia_gpu_devices
• kube_pod_container_resource_limits_nvidia_gpu_devices
• kube_node_status_capacity_nvidia_gpu_cards
• kube_node_status_allocatable_nvidia_gpu_cards

are removed in kube-state-metrics v1.4.0.

Any collectors and metrics based on alpha Kubernetes APIs are excluded from any stability guarantee, which may be changed at any given release.

See the Documentation directory for more informations of the exposed metrics.

Kube-state-metrics self metrics

kube-state-metrics exposes its own general process metrics under --telemetry-host and --telemetry-port (default 81).

Resource recommendation

Resource usage for kube-state-metrics changes with the Kubernetes objects(Pods/Nodes/Deployments/Secrects etc.) size of the cluster. To some extent, the Kubernetes objects in a cluster are in direct proportion to the node number of the cluster. addon-resizer can watch and automatically vertically scale the dependent container up and down based on the number of nodes. Thus kube-state-metrics uses addon-resizer to automatically scale its resource request. As for the detailed usage about addon-resizer please go to its ReadMe.

As a general rule, you should allocate

• 200MiB memory
• 0.1 cores

For clusters of more than 100 nodes, allocate at least

• 2MiB memory per node
• 0.001 cores per node

These numbers are based on scalability tests at 30 pods per node.

Note that if CPU limits are set too low, kube-state-metrics' internal queues will not be able to be worked off quickly enough, resulting in increased memory consumption as the queue length grows. If you experience problems resulting from high memory allocation, try increasing the CPU limits.

kube-state-metrics vs. metrics-server(Heapster)

metrics-server(Heapster) is a project which fetches metrics (such as CPU and memory utilization) from the Kubernetes API server and nodes and sends them to various time-series backends such as InfluxDB or Google Cloud Monitoring. Its most important function right now is implementing certain metric APIs that Kubernetes components like the horizontal pod auto-scaler query to make decisions.

While metrics-server(Heapster)'s focus is on forwarding metrics already generated by Kubernetes, kube-state-metrics is focused on generating completely new metrics from Kubernetes' object state (e.g. metrics based on deployments, replica sets, etc.). The reason not to extend metrics-server(Heapster) with kube-state-metrics' abilities is because the concerns are fundamentally different: metrics-server(Heapster) only needs to fetch, format and forward metrics that already exist, in particular from Kubernetes components, and write them into sinks, which are the actual monitoring systems. kube-state-metrics, in contrast, holds an entire snapshot of Kubernetes state in memory and continuously generates new metrics based off of it but has no responsibility for exporting its metrics anywhere.

In other words, kube-state-metrics itself is designed to be another source for metrics-server(Heapster) (although this is not currently the case).

Additionally, some monitoring systems such as Prometheus do not use metrics-server(Heapster) for metric collection at all and instead implement their own, but Prometheus can scrape metrics from metrics-server(Heapster) itself to alert on metrics-server(Heapster)'s health. Having kube-state-metrics as a separate project enables access to these metrics from those monitoring systems.

Setup

Install this project to your $GOPATH using go get:

go get k8s.io/kube-state-metrics

Building the Docker container

Simple run the following command in this root folder, which will create a self-contained, statically-linked binary and build a Docker image:

make container

Usage

Simply build and run kube-state-metrics inside a Kubernetes pod which has a service account token that has read-only access to the Kubernetes cluster.

Kubernetes Deployment

To deploy this project, you can simply run kubectl apply -f kubernetes and a Kubernetes service and deployment will be created. (Note: Adjust the apiVersion of some resource if your kubernetes cluster's version is not 1.8+, check the yaml file for more information). The service already has a prometheus.io/scrape: 'true' annotation and if you added the recommended Prometheus service-endpoint scraping configuration, Prometheus will pick it up automatically and you can start using the generated metrics right away.

Note: Google Kubernetes Engine (GKE) Users - GKE has strict role permissions that will prevent the kube-state-metrics roles and role bindings from being created. To work around this, you can give your GCP identity the cluster-admin role by running the following one-liner:

kubectl create clusterrolebinding cluster-admin-binding --clusterrole=cluster-admin --user=$(gcloud info | grep Account | cut -d '[' -f 2 | cut -d ']' -f 1)

Note that your GCP identity is case sensitive but gcloud info as of Google Cloud SDK 221.0.0 is not. This means that if your IAM member contains capital letters, the above one-liner may not work for you. If you have 403 forbidden responses after running the above command and kubectl apply -f kubernetes, check the IAM member associated with your account at https://console.cloud.google.com/iam-admin/iam?project=PROJECT_ID. If it contains capital letters, you may need to set the --user flag in the command above to the case-sensitive role listed at https://console.cloud.google.com/iam-admin/iam?project=PROJECT_ID.

After running the above, if you see Clusterrolebinding "cluster-admin-binding" created, then you are able to continue with the setup of this service.

Development

When developing, test a metric dump against your local Kubernetes cluster by running:

Users can override the apiserver address in KUBE-CONFIG file with --apiserver command line.

go install
kube-state-metrics --port=8080 --telemetry-port=8081 --kubeconfig=<KUBE-CONFIG> --apiserver=<APISERVER>

Then curl the metrics endpoint

curl localhost:8080/metrics