Scale for a MongoDB cluster

For MongoDB, vertical scaling is supported.

Vertical scaling

You can vertically scale a cluster by changing resource requirements and limits (CPU and storage). For example, if you need to change the resource demand from 1C2G to 2C4G, vertical scaling is what you need.

note

During the vertical scaling process, a restart is triggered and the primary pod may change after the restarting.

Before you start

Check whether the cluster status is Running. Otherwise, the following operations may fail.

kbcli cluster list mongodb-cluster

Steps

1. Change configuration. There are 3 ways to apply vertical scaling.

   Option 1. (Recommended) Use kbcli

   1. Use kbcli cluster vscale and configure the resources required.

      Example

      kbcli cluster vscale mongodb-cluster --components=mongodb --cpu=500m --memory=500Mi
      >
      OpsRequest mongodb-cluster-verticalscaling-thglk created successfully, you can view the progress:
             kbcli cluster describe-ops mongodb-cluster-verticalscaling-thglk -n default
   • --components describes the component name ready for vertical scaling.
   • --memory describes the requested and limited size of the component memory.
   • --cpu describes the requested and limited size of the component CPU.

   2. Validate the scaling with kbcli cluster describe-ops mongodb-cluster-verticalscaling-thglk -n default.

      note

      thglk is the OpsRequest number randomly generated in step 1.

   Option 2. Change the YAML file of the cluster

   Change the configuration of spec.components.resources in the YAML file. spec.components.resources controls the requirement and limit of resources and changing them triggers a vertical scaling.

   Example

   apiVersion: apps.kubeblocks.io/v1alpha1
   kind: Cluster
   metadata:
     name: mongodb-cluster
     namespace: default
   spec:
     clusterDefinitionRef: mongodb
     clusterVersionRef: mongodb-5.0
     componentSpecs:
     - name: mongodb
       componentDefRef: mongodb
       replicas: 1
       resources: # Change the values of resources.
         requests:
           memory: "2Gi"
           cpu: "1000m"
         limits:
           memory: "4Gi"
           cpu: "2000m"
       volumeClaimTemplates:
       - name: data
         spec:
           accessModes:
             - ReadWriteOnce
           resources:
             requests:
               storage: 1Gi
     terminationPolicy: Halt

2. Validate the vertical scaling.

   kbcli cluster list mongodb-cluster
   >
   NAME              NAMESPACE   CLUSTER-DEFINITION   VERSION          TERMINATION-POLICY   STATUS    CREATED-TIME                 
   mongodb-cluster   default     mongodb              mongodb-5.0   WipeOut              Running   Apr 26,2023 11:50 UTC+0800  

   • STATUS=VerticalScaling: it means the vertical scaling is in progress.

   • STATUS=Running: it means the vertical scaling operation has been applied.

   • STATUS=Abnormal: it means the vertical scaling is abnormal. The reason may be the normal instances number is less than the total instance number or the leader instance is running properly while others are abnormal.

     note

     To solve the problem, you can check manually to see whether resources are sufficient. If AutoScaling is supported, the system recovers when there are enough resources, otherwise, you can create enough resources and check the result with kubectl describe command.

     note

     Vertical scaling does not synchronize parameters related to CPU and memory and it is required to manually call the OpsRequest of configuration to change parameters accordingly. Refer to Configuration for instructions.

3. Check whether the corresponding resources change.

   kbcli cluster describe mongodb-cluster