Usage Metrics Collector

The usage-metrics-collector is a Prometheus metrics collector optimized for collecting kube usage and capacity metrics.

Motivation

Why not just use promql and recording rules?

• Scale
  • Aggregate at collection time to reduce prometheus work
  • Export aggregated metrics without the raw metrics to reduce prometheus storage
• Insight
  • Join labels at collection time (e.g. set the priority class on pod metrics)
  • Set hard to resolve labels (e.g. set the workload kind on pod metrics)
  • View node-level cgroup utilization (e.g. kubepods vs system.slice metrics)
• Fidelity
  • Scrape utilization at 1s intervals as raw metrics
  • Perform aggregations on the 1s interval metrics (e.g. get the p95 1s utilization sample for all replicas of a workload)

Example

collector.yaml

Architecture

considerations

• Metrics must be highly configurable
  • The metrics labels derived from objects
  • The aggregations (sum, average, median, max, p95, histograms, etc) must be configurable
• Metrics should be able to be pushed to additional sources such as cloud storage buckets, BigQuery, etc
• Metric computation must scale to large clusters with lots of churn.
  • Run aggregations in parallel
  • Re-use previous results as much as possible
• Scrapes should always immediately get a result, even when complex aggregations in large clusters take minutes to compute.
• Utilization metrics should not be published until the data is present from a sufficient number of nodes. This is to prevent showing "low" utilization numbers before all nodes have sent results.
• There should be no graphs in data. There must always be at least 1 ready and healthy replica which can be scraped by prometheus.
• Sampler pods which become unhealthy due to issues on a node should be continuously recreated until they are functional again.
• All cluster objects and utilization samples are cached in the collector so memory must be optimized.
• It is difficult to horizontally scale the collector. Offloading computations to the samplers is preferred.

metrics-node-sampler

• Runs as a DaemonSet on each Node
• Periodically reads utilization data for cpu and memory and stores in ring buffer
  • Period and number of samples is configurable
• Reads host metrics directly from cgroups psuedo filesystem (e.g. cpu usage for all of kubepods cgroup)
• Reads container metrics from containerd (e.g. cpu usage for an individual container)
• Periodically pushes metrics to collectors
  • After time period
  • After new pod starts running
  • Before shutting down
• Finds collectors to push to via DNS
• Collectors can register manually with each sampler
• Performs some precomputations such as averages.

metrics-prometheus-collector

• Runs as a Deployment with multiple replicas for HA
• Highly configurable metrics
  • Metric labels may be derived from annotations / labels on other objects (e.g. pod metrics should have metric labels pulled from node conditions)
  • Metrics may be pre-aggregated prior to being scraped by prometheus (e.g. reduce cardinality, produce quantiles and histograms)
• Periodically get the metrics and cache them to be scraped (i.e. minimize scrape time by eagerly computing results)
• Registers itself and all collector replicas with each sampler
• Recieves metrics from node-samplers as a utilization source
• Waits until has sufficient samples before providing results
• Waits until results have been scraped before marking self as Ready
• Can write additional metrics to local files

collector side-cars

• May expose additional metrics read from external sources
• May write local files to persistent storage for futher analysis

Exposed Metrics

A sample of the exposed metrics is available in METRICS.md.

In addition to these metrics, a series of performance related metrics are published for the collection process. These metrics are documented in performance analysis document.

Getting started

Note: No usage-metrics-collector container image is publicly hosted. Folks will need to build and publish this own until this is resolved.

Installing into a cluster

Kind cluster

Important: requires using cgroups v1.

• Must set for Docker on Mac using these docs
• Must set for GKE for 1.26+ clusters

1. Create a kind cluster

• kind create cluster

2. Build the image

• docker build . -t usage-metrics-collector:v0.0.0

3. Load the image into kind

• kind load docker-image usage-metrics-collector:v0.0.0

4. Install the config

• kustomize build config | kubectl apply -f -

5. Update your context to use the usage-metrics-collector namespace by default

• kubectl config set-context --current --namespace=usage-metrics-collector

Kicking the tires

1. Make sure the pods are healthy

• kubectl get pods

2. Make sure the services have endpoints

• kubectl describe services

3. Get the metrics from the collector itself

• kubectl exec -t -i $(kubectl get pods -o name -l app=metrics-prometheus-collector) -- curl localhost:8080/metrics
• wait for service to be ready
• kubectl port-forward service/metrics-prometheus-collector 8080:8080
• visit localhost:8080/metrics in your browser

4. Get the metrics from prometheus

• kubectl port-forward $(kubectl get pods -o name -l app=prometheus) 9090:9090
• visit localhost:9090/ in your browser

5. View the metrics in Grafana

• kubectl port-forward service/grafana 3000:3000
• visit localhost:3000 in your browser
• enter admin for the username and password
• go to "Explore"
• change the source to "prometheus"
• enter kube_usage_ into the metric field
• remove the label filters
• click "Run Query"

Specifying aggregation rules

1. Edit config/metrics-prometheus-collector/configmaps/collector.yaml
2. Run make run-local
3. View the updated metrics in grafana

Code of conduct

Participation in the Kubernetes community is governed by the Kubernetes Code of Conduct.