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Prescaling-exporter

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.

Requirements

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.

Install

Kubernetes Deployement

  • Clone repo
  • Run this command with Helm3
helm install prescaling-exporter ./helm/prescaling-exporter -n prescaling-exporter --create-namespace

You can use skaffold if you want.

Configure an Horizontal Pod Autoscaler

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.value to 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%.

Configure prometheus adapter

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"

Configure parameters

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

Prescaling Web server

OpenAPI docs

This application provides a swagger UI which is accessible on /swagger/index.html.

Event API

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/.

Metrics

The metrics are exposed on /metrics endpoint.

Build

Golang utils

  1. Golang build
./generate_type.sh
go build
  1. Run test
go test -v ./...
  1. Run test with coverate report
 go test -coverprofile=cover.out -v ./...   
openapi-generator generate -i api/openapi.yaml -g go-server -o .

Generate crd files

./generate_type.sh

Generate swagger docs

go install github.com/swaggo/swag/cmd/swag@latest
swag init -g pkg/server/server.go --parseInternal=true