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ClickHouseAutoscaler

What is ClickHouseAutoscaler

ClickHouseAutoscaler is a Kubernetes Custom Resource Definitions (CRD). It provides a declarative configuration for autoscaling ClickHouse compute resources and storage of database components in a Kubernetes native way.

ClickHouseAutoscaler CRD Specifications

Like any official Kubernetes resource, a ClickHouseAutoscaler has TypeMeta, ObjectMeta, Spec and Status sections.

Here, some sample ClickHouseAutoscaler CROs for autoscaling different components of database is given below:

Sample ClickHouseAutoscaler for clickhouse cluster:

apiVersion: autoscaling.kubedb.com/v1alpha1
kind: ClickHouseAutoscaler
metadata:
  name: ch-compute-autoscale
  namespace: demo
spec:
  databaseRef:
    name: clickhouse-prod
  compute:
    clickhouse:
      trigger: "On"
      podLifeTimeThreshold: 5m
      resourceDiffPercentage: 20
      minAllowed:
        cpu: 1
        memory: 2Gi
      maxAllowed:
        cpu: 2
        memory: 3Gi
      controlledResources: ["cpu", "memory"]
      containerControlledValues: "RequestsAndLimits"

Here, we are going to describe the various sections of a ClickHouseAutoscaler crd.

A ClickHouseAutoscaler object has the following fields in the spec section.

spec.databaseRef

spec.databaseRef is a required field that point to the ClickHouse object for which the autoscaling will be performed. This field consists of the following sub-field:

• spec.databaseRef.name : specifies the name of the ClickHouse object.

spec.opsRequestOptions

These are the options to pass in the internally created opsRequest CRO. opsRequestOptions has two fields.

spec.compute

spec.compute specifies the autoscaling configuration for the compute resources i.e. cpu and memory of the database components. This field consists of the following sub-field:

• spec.compute.clickhouse indicates the desired compute autoscaling configuration for ClickHouse database.

spec.compute.clickhouse has the following sub-fields:

• trigger indicates if compute autoscaling is enabled for this component of the database. If “On” then compute autoscaling is enabled. If “Off” then compute autoscaling is disabled.
• minAllowed specifies the minimal amount of resources that will be recommended, default is no minimum.
• maxAllowed specifies the maximum amount of resources that will be recommended, default is no maximum.
• controlledResources specifies which type of compute resources (cpu and memory) are allowed for autoscaling. Allowed values are “cpu” and “memory”.
• containerControlledValues specifies which resource values should be controlled. Allowed values are “RequestsAndLimits” and “RequestsOnly”.
• resourceDiffPercentage specifies the minimum resource difference between recommended value and the current value in percentage. If the difference percentage is greater than this value than autoscaling will be triggered.
• podLifeTimeThreshold specifies the minimum pod lifetime of at least one of the pods before triggering autoscaling.

There are two more fields, those are only specifiable for the percona variant inMemory databases.

• inMemoryStorage.UsageThresholdPercentage If db uses more than usageThresholdPercentage of the total memory, memoryStorage should be increased.
• inMemoryStorage.ScalingFactorPercentage If db uses more than usageThresholdPercentage of the total memory, memoryStorage should be increased by this given scaling percentage.

spec.storage

spec.storage specifies the autoscaling configuration for the storage resources of the database components. This field consists of the following sub-field:

• spec.storage.clickhouse indicates the desired storage autoscaling configuration for ClickHouse cluster.

All of them has the following sub-fields:

• trigger indicates if storage autoscaling is enabled for this component of the database. If “On” then storage autoscaling is enabled. If “Off” then storage autoscaling is disabled.
• usageThreshold indicates usage percentage threshold, if the current storage usage exceeds then storage autoscaling will be triggered.
• scalingThreshold indicates the percentage of the current storage that will be scaled.
• expansionMode indicates the volume expansion mode.