MongoDB Replicated Cluster

MongoDB cluster configuration is easily customizable using helm as well kubectl. Since all the configurations are in the form YAML file, it can be easily changed and customized.

The values.yaml file for MongoDB cluster setup can be found here. But if the setup is not done using Helm, in that case Kubernetes manifests needs to be customized.

Parameters for Helm Chart

Parameters for CRD Object Definition

These are the parameters that are currently supported by the MongoDB operator for the cluster MongoDB database setup:-

• clusterSize
• kubernetesConfig
• storage
• mongoDBSecurity
• mongoDBMonitoring

clusterSize

clusterSize is the size of MongoDB replicated cluster. We have to provide the number of node count that we want to make part of MongoDB cluster. For example:- 1 primary and 2 secondary is 3 as pod count.

  clusterSize: 3

kubernetesConfig

kubernetesConfig is the general configuration paramater for MongoDB CRD in which we are defining the Kubernetes related configuration details like- image, tag, imagePullPolicy, and resources.

  kubernetesConfig:
    image: quay.io/opstree/mongo:v5.0
    imagePullPolicy: IfNotPresent
    resources:
      requests:
        cpu: 1
        memory: 8Gi
      limits:
        cpu: 1
        memory: 8Gi
    imagePullSecret: regcred

NodeSelector:- nodeSelector is the simplest recommended form of node selection constraint. nodeSelector is a field of PodSpec. It specifies a map of key-value pairs.

  kubernetesConfig:
    nodeSelector:
      beta.kubernetes.io/os: linux

Affinity:- The affinity/anti-affinity feature, greatly expands the types of constraints you can express. The affinity/anti-affinity language is more expressive. The language offers more matching rules besides exact matches created with a logical AND operation.

  kubernetesConfig:
    mongoAffinity:
      nodeAffinity:
        requiredDuringSchedulingIgnoredDuringExecution:
          nodeSelectorTerms:
            - matchExpressions:
                - key: beta.kubernetes.io/os
                  operator: In
                  values:
                    - linux

PriorityClassName:- A PriorityClass is a non-namespaced object that defines a mapping from a priority class name to the integer value of the priority. The name is specified in the name field of the PriorityClass object’s metadata. The value is specified in the required value field.

  kubernetesConfig:
    priorityClassName: system-node-critical

Tolerations:- Tolerations are applied to pods, and allow (but do not require) the pods to schedule onto nodes with matching taints.

  kubernetesConfig:
    tolerations:
      - key: "example-key"
        operator: "Exists"
        effect: "NoSchedule"

SecurityContext:- A security context defines privilege and access control settings for a Pod or Container. The security settings that you specify for a Pod apply to all Containers in the Pod.

    securityContext:
      fsGroup: 1001

storage

storage is the storage specific configuration for MongoDB CRD. With this parameter we can make enable persistence inside the MongoDB statefulset. In this parameter, we will provide inputs like- accessModes, size of the storage, and storageClass.

  storage:
    accessModes: ["ReadWriteOnce"]
    storageSize: 1Gi
    storageClass: csi-cephfs-sc

mongoDBSecurity

mongoDBSecurity is the security specification for MongoDB CRD. If we want to enable our MongoDB database authenticated, in that case, we can enable this configuration. To enable the authentication we need to provide paramaters like- admin username, secret reference in Kubernetes.

  mongoDBSecurity:
    mongoDBAdminUser: admin
    secretRef:
      name: mongodb-secret
      key: password

mongoDBMonitoring

mongoDBMonitoring is the monitoring feature for MongoDB CRD. By using this parameter we can enable the MongoDB monitoring using MongoDB Exporter. In this parameter, we need to provide image, imagePullPolicy and resources for mongodb exporter.

  mongoDBMonitoring:
    enableExporter: true
    image: bitnami/mongodb-exporter:0.11.2-debian-10-r382
    imagePullPolicy: IfNotPresent
    resources: {}