kube-state-metrics

README

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.

The metrics are exported through the Prometheus golang client on the HTTP endpoint /metrics on the listening port (default 8080). They are served either as plaintext or protobuf depending on the Accept header. 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
• Resource recommendation
• kube-state-metrics vs. Heaspter
• Setup
  • Building the Docker container
• Usage
  • Kubernetes Deployment
  • Deployment

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. Currently, client-go is in version release-5.0.

Compatibility matrix

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

kube-state-metrics	client-go	Kubernetes 1.4	Kubernetes 1.5	Kubernetes 1.6	Kubernetes 1.7	Kubernetes 1.8
v0.4.0	v2.0.0-alpha.1	✓	✓	-	-	-
v0.5.0	v2.0.0-alpha.1	✓	✓	-	-	-
v1.0.x	4.0.0-beta.0	✓	✓	✓	✓	-
master	release-5.0	✓	✓	✓	✓	✓

• ✓ 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:v1.0.1
• gcr.io/google_containers/kube-state-metrics:v1.0.1

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

• 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 in alpha stage and will be deprecated when the kubernetes gpu support is final in 1.9 version.

See the Documentation directory for documentation of the exposed metrics.

Resource recommendation

Resource usage changes with the size of the cluster. 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.

kube-state-metrics vs. Heapster

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 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 Heapster with kube-state-metrics' abilities is because the concerns are fundamentally different: 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 Heapster (although this is not currently the case).

Additionally, some monitoring systems such as Prometheus do not use Heapster for metric collection at all and instead implement their own, but Prometheus can scrape metrics from heapster itself to alert on 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. 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.

Development

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

go install
kube-state-metrics --apiserver=<APISERVER-HERE> --in-cluster=false --port=8080

Then curl the metrics endpoint

curl localhost:8080/metrics