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MongoDBAutoscaler

What is MongoDBAutoscaler

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

MongoDBAutoscaler CRD Specifications

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

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

Sample MongoDBAutoscaler for standalone database:

apiVersion: autoscaling.kubedb.com/v1alpha1
kind: MongoDBAutoscaler
metadata:
  name: mg-as
  namespace: demo
spec:
  databaseRef:
    name: mg-standalone
  opsRequestOptions:
    readinessCriteria:
      oplogMaxLagSeconds: 20
      objectsCountDiffPercentage: 10
    timeout: 3m
    apply: IfReady
  compute:
    standalone:
      trigger: "On"
      podLifeTimeThreshold: 24h
      minAllowed:
        cpu: 250m
        memory: 350Mi
      maxAllowed:
        cpu: 1
        memory: 1Gi
      controlledResources: ["cpu", "memory"]
      containerControlledValues: "RequestsAndLimits"
      resourceDiffPercentage: 10
  storage:
    standalone:
      expansionMode: "Online"
      trigger: "On"
      usageThreshold: 60
      scalingThreshold: 50

Sample MongoDBAutoscaler for replicaset database:

apiVersion: autoscaling.kubedb.com/v1alpha1
kind: MongoDBAutoscaler
metadata:
  name: mg-as-rs
  namespace: demo
spec:
  databaseRef:
    name: mg-rs
  opsRequestOptions:
    readinessCriteria:
      oplogMaxLagSeconds: 20
      objectsCountDiffPercentage: 10
    timeout: 3m
    apply: IfReady
  compute:
    replicaSet:
      trigger: "On"
      podLifeTimeThreshold: 24h
      minAllowed:
        cpu: 200m
        memory: 300Mi
      maxAllowed:
        cpu: 1
        memory: 1Gi
      controlledResources: ["cpu", "memory"]
      containerControlledValues: "RequestsAndLimits"
      resourceDiffPercentage: 10
  storage:
    replicaSet:
      expansionMode: "Online"
      trigger: "On"
      usageThreshold: 60
      scalingThreshold: 50

Sample MongoDBAutoscaler for sharded database:

apiVersion: autoscaling.kubedb.com/v1alpha1
kind: MongoDBAutoscaler
metadata:
  name: mg-as-sh
  namespace: demo
spec:
  databaseRef:
    name: mg-sh
  opsRequestOptions:
    readinessCriteria:
      oplogMaxLagSeconds: 20
      objectsCountDiffPercentage: 10
    timeout: 3m
    apply: IfReady
  compute:
    shard:
      trigger: "On"
      podLifeTimeThreshold: 24h
      minAllowed:
        cpu: 250m
        memory: 350Mi
      maxAllowed:
        cpu: 1
        memory: 1Gi
      controlledResources: ["cpu", "memory"]
      containerControlledValues: "RequestsAndLimits"
      resourceDiffPercentage: 10
    configServer:
      trigger: "On"
      podLifeTimeThreshold: 24h
      minAllowed:
        cpu: 250m
        memory: 350Mi
      maxAllowed:
        cpu: 1
        memory: 1Gi
      controlledResources: ["cpu", "memory"]
      containerControlledValues: "RequestsAndLimits"
      resourceDiffPercentage: 10
    mongos:
      trigger: "On"
      podLifeTimeThreshold: 24h
      minAllowed:
        cpu: 250m
        memory: 350Mi
      maxAllowed:
        cpu: 1
        memory: 1Gi
      controlledResources: ["cpu", "memory"]
      containerControlledValues: "RequestsAndLimits"
      resourceDiffPercentage: 10
  storage:
    shard:
      expansionMode: "Online"
      trigger: "On"
      usageThreshold: 60
      scalingThreshold: 50
    configServer:
      expansionMode: "Online"
      trigger: "On"
      usageThreshold: 60
      scalingThreshold: 50

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

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

spec.databaseRef

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

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

spec.opsRequestOptions

These are the options to pass in the internally created opsRequest CRO. opsRequestOptions has three fields. They have been described in details here.

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.standalone indicates the desired compute autoscaling configuration for a standalone MongoDB database.
• spec.compute.replicaSet indicates the desired compute autoscaling configuration for replicaSet of a MongoDB database.
• spec.compute.configServer indicates the desired compute autoscaling configuration for config servers of a sharded MongoDB database.
• spec.compute.mongos indicates the desired compute autoscaling configuration for the mongos nodes of a sharded MongoDB database.
• spec.compute.shard indicates the desired compute autoscaling configuration for the shard nodes of a sharded MongoDB database.
• spec.compute.arbiter indicates the desired compute autoscaling configuration for the arbiter node.

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

• spec.compute.standalone indicates the desired storage autoscaling configuration for a standalone MongoDB database.
• spec.compute.replicaSet indicates the desired storage autoscaling configuration for replicaSet of a MongoDB database.
• spec.compute.configServer indicates the desired storage autoscaling configuration for config servers of a sharded MongoDB database.
• spec.compute.shard indicates the desired storage autoscaling configuration for the shard nodes of a sharded MongoDB database.

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.