This project is a Prometheus exporter written in Golang, its goal is to provide a metric that scales applications to a requested capacity on a daily time slot or on an event declared in the embedded api.
The exporter exposes a metric calculated according to the annotations defined on the HPA. The project also exposes an API that allows to register an event with a capacity multiplier.
- Prometheus Stack or Victoria Metrics Stack
- Prometheus Adapater
Info: It is quite possible to use this solution with another observability stack than Prometheus. For example, Datadog or Newrelic, but we do not provide a configuration example.
- Clone repo
- Run this command with Helm3
helm install prescaling-exporter ./helm/prescaling-exporter -n prescaling-exporter --create-namespaceYou can use skaffold if you want.
To be able to pre-scale an application every day before a traffic spike, you must add the following annotations on the HPA:
| Annotations | values |
|---|---|
| annotations.scaling.exporter.time.start | "hh:mm:ss" |
| annotations.scaling.exporter.time.end | "hh:mm:ss" |
| annotations.scaling.exporter.replica.min | "integer" |
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
name: "{{ .Release.Name }}"
annotations:
annotations.scaling.exporter.replica.min: "{{ .Values.hpa.annotations.replica_min"
annotations.scaling.exporter.time.end: "{{ .Values.hpa.annotations.time_end }}"
annotations.scaling.exporter.time.start: "{{ .Values.hpa.annotations.time_start }}"
spec:
scaleTargetRef:
apiVersion: apps/v1
kind: Deployment
name: "{{ .Release.Name }}"
minReplicas: {{ .Values.hpa.minReplicas }}
maxReplicas: {{ .Values.hpa.maxReplicas }}
metrics:
- type: External
external:
metric:
name: "prescaling_metric"
selector:
matchLabels:
deployment: "{{ .Release.Name }}"
target
type: Value
value: 10
It's important to set the
target.valueto 10. The metric's value provided by the exporter in order to scale is 11. The scale up of pods will be gradual. Currently, the increment is carried out 10% by 10%.
Here is a configuration example using the prometheus adapter to supply the metric to the Kubernetes cluster:
- "metricsQuery": "avg(<<.Series>>{<<.LabelMatchers>>})"
"name":
"as": "prescaling_metric"
"resources":
"overrides":
"namespace":
"resource": "namespace"
"seriesQuery": "prescaling_metric"
You can modify the application's settings to use different annotations or a different port. Configurable variable environments in the chart values are used to do this:
| Parameters | Default values | Comment |
|---|---|---|
| Namespace | "prescaling-exporter" | Namespace for the prescaling stack |
| Port | "9101" | Application port |
| AnnotationEndTime | "annotations.scaling.exporter.time.end" | Prescaling end time |
| AnnotationStartTime | "annotations.scaling.exporter.time.start" | Prescaling start time |
| AnnotationMinReplicas | "annotations.scaling.exporter.replica.min" | Minimum of desired replicas during the prescaling |
| LabelProject | "project" | k8s label used to add a label in the prescaling metric |
This application provides a swagger UI which is accessible on /swagger/index.html.
To allow the platform to scale up and down on different schedules and with a multiplier, prescaling events can be registered by the DRBs or the API.
The following API allows the creation, modification and deletion of Prescaling Event CRDs in the cluster: /api/v1/events/.
The metrics are exposed on /metrics endpoint.
- Golang build
./generate_type.sh
go build- Run test
go test -v ./...- Run test with coverate report
go test -coverprofile=cover.out -v ./... openapi-generator generate -i api/openapi.yaml -g go-server -o .
./generate_type.sh
go install github.com/swaggo/swag/cmd/swag@latest
swag init -g pkg/server/server.go --parseInternal=true