How To set up a MongoDB Kubernetes Installation

2023-03-16

Prerequisites

  • Basic Understanding of Kubernetes and Helm.
  • Minikube setup

How to Guide

Start up the Minikube cluster

1
2
minikube start --cpus 4 --memory 4096
kubectl get nodes

Install MongoDB Community Kubernetes Operator via Helm chart

There are so many helm charts versions of MongoDB, but we will be installing community-operator version.

1
2
3
4
5
6
7
8
9
10
#values.yaml
operator:
  # Resources allocated to Operator Pod
  resources:
    limits:
      cpu: 500m
      memory: 200Mi
    requests:
      cpu: 250m
      memory: 150Mi
1
2
3
export KUBE_NAMESPACE=infra
kubectl create namespace $KUBE_NAMESPACE
helm  upgrade -f values.yaml --install community-operator mongodb/community-operator --namespace $KUBE_NAMESPACE

Deploy a MongoDB Replica Set

These are detailed guides on modifying your YAML files for deploying MongoDB replica sets.
I will modify the following guide to the YAML below.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
#mongo.yal
---
apiVersion: mongodbcommunity.mongodb.com/v1
kind: MongoDBCommunity
metadata:
  name: mongodb
spec:
  members: 3
  type: ReplicaSet
  version: "4.2.6"
  security:
    authentication:
      modes: ["SCRAM"]
  users:
    - name: root-user
      db: admin
      passwordSecretRef: # a reference to the secret that will be used to generate the user's password
        name: mongo-creds
      roles:
        - name: clusterAdmin
          db: admin
        - name: userAdminAnyDatabase
          db: admin
      scramCredentialsSecretName: my-scram
  additionalMongodConfig:
    storage.wiredTiger.engineConfig.journalCompressor: zlib

# the user credentials will be generated from this secret
# once the credentials are generated, this secret is no longer required
---
apiVersion: v1
kind: Secret
metadata:
  name: mongo-creds
type: Opaque
stringData:
  password: rtfTTUIgu7890ggt#ioo123
1
2
3
kubectl apply -f mongo.yaml  --namespace $KUBE_NAMESPACE
kubectl get mdbc  --namespace $KUBE_NAMESPACE
kubectl get pods -n $KUBE_NAMESPACE

Output:

1
2
3
4
5
6
7
NAME      PHASE     VERSION
mongodb   Running   4.2.6
NAME                                          READY   STATUS    RESTARTS   AGE
mongodb-0                                     2/2     Running   0          6m29s
mongodb-1                                     2/2     Running   0          87s
mongodb-2                                     2/2     Running   0          46s
mongodb-kubernetes-operator-6465d9cd7-qpkzs   1/1     Running   0          7m3s

Create a new user on the primary replica

Create a new user to avoid the following error MongoDB - admin user not authorized

  1. ssh into the 3 MongoDB replicas
1
2
3
kubectl exec -it mongodb-0 --namespace $KUBE_NAMESPACE -- sh
kubectl exec -it mongodb-1 --namespace $KUBE_NAMESPACE -- sh
kubectl exec -it mongodb-1 --namespace $KUBE_NAMESPACE -- sh
  1. When the # prompt appears, type: mongo
  2. Look out for the primary replica because this is the only member in the replica set that receives write operations.
1
2
3
4
5
6
MongoDB shell version v4.2.6
connecting to: mongodb://127.0.0.1:27017/?compressors=disabled&gssapiServiceName=mongodb
Implicit session: session { "id" : UUID("ccdd585d-2212-451c-b58f-9a42b4a52894") }
MongoDB server version: 4.2.6
........
mongodb:PRIMARY>
  1. I will terminate other 2 sessions and use kubectl exec -it mongodb-1 --namespace $KUBE_NAMESPACE -- sh, that is the primary replica
  2. initiate the replica set with rs.initiate()
  3. Switch to the test database: use admin
  4. Authenticate with the username and password specified in mongo.yaml file : db.auth('root-user','rtfTTUIgu7890ggt#ioo123')
  5. Create a new user : db.createUser({ user:"oluchi", pwd: "oluchitest", roles: [{role: "readWrite", db: "admin"}] })

Output

1
2
3
4
5
6
7
8
9
10
11
mongodb:PRIMARY> db.createUser({ user:"oluchi", pwd: "fGJYIIhhjkuchitest", roles: [{role: "readWrite", db: "admin"}]})
Successfully added user: {
        "user" : "oluchi",
        "roles" : [
                {
                        "role" : "readWrite",
                        "db" : "admin"
                }
        ]
}