Deploy MongoDB ReplicaSet with Arbiter in Google Kubernetes Engine (GKE) using KubeDB


KubeDB is the Kubernetes Native Database Management Solution which simplifies and automates routine database tasks such as Provisioning, Monitoring, Upgrading, Patching, Scaling, Volume Expansion, Backup, Recovery, Failure detection, and Repair for various popular databases on private and public clouds. The databases that KubeDB supports are MongoDB, Elasticsearch, MySQL, MariaDB, Kafka, Redis, PostgreSQL, ProxySQL, Percona XtraDB, Memcached and PgBouncer. You can find the guides to all the supported databases in KubeDB . In this tutorial we will deploy MongoDB ReplicaSet with Arbiter in Google Kubernetes Engine (GKE). We will cover the following steps:

  1. Install KubeDB
  2. Deploy MongoDB ReplicaSet with Arbiter
  3. Connect MongoDB with Arbiter
  4. Read/Write with Arbiter

Get Cluster ID

We need the cluster ID to get the KubeDB License. To get cluster ID, we can run the following command:

$ kubectl get ns kube-system -o jsonpath='{.metadata.uid}'

Get License

Go to Appscode License Server to get the license.txt file. For this tutorial we will use KubeDB Enterprise Edition.

License Server

Install KubeDB

We will use helm to install KubeDB. Please install helm here if it is not already installed. Now, let’s install KubeDB.

$ helm repo add appscode
$ helm repo update

$ helm search repo appscode/kubedb
NAME                              	CHART VERSION	APP VERSION	DESCRIPTION                                       
appscode/kubedb                   	v2023.06.19  	v2023.06.19	KubeDB by AppsCode - Production ready databases...
appscode/kubedb-autoscaler        	v0.19.0      	v0.19.0    	KubeDB Autoscaler by AppsCode - Autoscale KubeD...
appscode/kubedb-catalog           	v2023.06.19  	v2023.06.19	KubeDB Catalog by AppsCode - Catalog for databa...
appscode/kubedb-community         	v0.24.2      	v0.24.2    	KubeDB Community by AppsCode - Community featur...
appscode/kubedb-crds              	v2023.06.19  	v2023.06.19	KubeDB Custom Resource Definitions                
appscode/kubedb-dashboard         	v0.10.0      	v0.10.0    	KubeDB Dashboard by AppsCode                      
appscode/kubedb-enterprise        	v0.11.2      	v0.11.2    	KubeDB Enterprise by AppsCode - Enterprise feat...
appscode/kubedb-grafana-dashboards	v2023.06.19  	v2023.06.19	A Helm chart for kubedb-grafana-dashboards by A...
appscode/kubedb-metrics           	v2023.06.19  	v2023.06.19	KubeDB State Metrics                              
appscode/kubedb-one               	v2023.06.19  	v2023.06.19	KubeDB and Stash by AppsCode - Production ready...
appscode/kubedb-ops-manager       	v0.21.0      	v0.21.2    	KubeDB Ops Manager by AppsCode - Enterprise fea...
appscode/kubedb-opscenter         	v2023.06.19  	v2023.06.19	KubeDB Opscenter by AppsCode                      
appscode/kubedb-provisioner       	v0.34.0      	v0.34.1    	KubeDB Provisioner by AppsCode - Community feat...
appscode/kubedb-schema-manager    	v0.10.0      	v0.10.0    	KubeDB Schema Manager by AppsCode                 
appscode/kubedb-ui                	v2023.03.23  	0.3.33-rc.2	A Helm chart for Kubernetes                       
appscode/kubedb-ui-server         	v2021.12.21  	v2021.12.21	A Helm chart for kubedb-ui-server by AppsCode     
appscode/kubedb-webhook-server    	v0.10.0      	v0.10.0    	KubeDB Webhook Server by AppsCode  

# Install KubeDB Enterprise operator chart
$ helm install kubedb appscode/kubedb \
  --version v2023.06.19 \
  --namespace kubedb --create-namespace \
  --set kubedb-provisioner.enabled=true \
  --set kubedb-ops-manager.enabled=true \
  --set kubedb-autoscaler.enabled=true \
  --set kubedb-dashboard.enabled=true \
  --set kubedb-schema-manager.enabled=true \
  --set-file global.license=/path/to/the/license.txt

Let’s verify the installation:

$ kubectl get pods --all-namespaces -l ""
NAMESPACE   NAME                                           READY   STATUS    RESTARTS        AGE
kubedb      kubedb-kubedb-autoscaler-55f9786544-kmm4n      1/1     Running   0               2m18s
kubedb      kubedb-kubedb-dashboard-85c67f6d7b-gk56c       1/1     Running   0               2m18s
kubedb      kubedb-kubedb-ops-manager-774cf744d8-zxl4v     1/1     Running   0               2m18s
kubedb      kubedb-kubedb-provisioner-f65f87bbb-jcr7r      1/1     Running   0               2m18s
kubedb      kubedb-kubedb-schema-manager-bcf6587fd-qcpqx   1/1     Running   0               2m18s
kubedb      kubedb-kubedb-webhook-server-cb4544c9d-5czrg   1/1     Running   0               2m18s

We can list the CRD Groups that have been registered by the operator by running the following command:

$ kubectl get crd -l
NAME                                              CREATED AT   2023-08-08T10:58:44Z      2023-08-08T10:58:45Z                        2023-08-08T10:58:47Z           2023-08-08T10:59:00Z          2023-08-08T10:56:21Z                                  2023-08-08T10:58:59Z                   2023-08-08T10:56:21Z                                 2023-08-08T10:59:21Z                  2023-08-08T10:56:21Z         2023-08-08T10:58:44Z                2023-08-08T10:58:57Z                 2023-08-08T10:59:29Z                               2023-08-08T10:58:59Z                2023-08-08T10:56:22Z                             2023-08-08T10:59:03Z              2023-08-08T10:56:22Z         2023-08-08T10:58:44Z                2023-08-08T10:58:48Z                 2023-08-08T10:59:05Z                               2023-08-08T10:58:51Z                2023-08-08T10:56:23Z           2023-08-08T10:58:44Z                  2023-08-08T10:58:44Z                   2023-08-08T10:59:26Z                                 2023-08-08T10:58:45Z                  2023-08-08T10:56:23Z   2023-08-08T10:58:44Z           2023-08-08T10:59:44Z                         2023-08-08T10:59:16Z          2023-08-08T10:56:23Z                             2023-08-08T10:59:16Z              2023-08-08T10:56:23Z        2023-08-08T10:58:44Z               2023-08-08T10:58:54Z                             2023-08-08T10:58:56Z                2023-08-08T10:59:37Z               2023-08-08T10:56:24Z        2023-08-08T10:58:45Z                2023-08-08T10:59:40Z                              2023-08-08T10:59:19Z               2023-08-08T10:56:24Z                    2023-08-08T10:59:55Z           2023-08-08T10:58:45Z                                2023-08-08T10:59:19Z                   2023-08-08T10:59:33Z   2023-08-08T10:58:46Z           2023-08-08T10:59:48Z                         2023-08-08T10:59:20Z                  2023-08-08T10:56:24Z                   2023-08-08T10:59:58Z

Deploy MongoDB Cluster with Arbiter

We are going to Deploy MongoDB Cluster with Arbiter by using KubeDB. First, let’s create a Namespace in which we will deploy the database.

$ kubectl create namespace demo
namespace/demo created

Here is the yaml of the MongoDB CRO we are going to use:

kind: MongoDB
  name: mongodb
  namespace: demo
  version: "6.0.5"
    name: "rs0"
  replicas: 2
  storageType: Durable
    storageClassName: "standard"
      - ReadWriteOnce
        storage: 512Mi
    podTemplate: {}
  terminationPolicy: WipeOut

Let’s save this yaml configuration into mongodb.yaml Then create the above MongoDB CRO

$ kubectl apply -f mongodb.yaml created

In this yaml,

  • spec.version field specifies the version of MongoDB. Here, we are using MongoDB version 6.0.5. You can list the KubeDB supported versions of MongoDB by running $ kubectl get mongodbversions command.
  • is the name of the StorageClass used to provision PVCs.
  • spec.arbiter denotes arbiter spec of the deployed MongoDB CRD. There are two fields under it, configSecret & podTemplate. spec.arbiter.configSecret is an optional field to provide custom configuration file for database (i.e mongod.cnf). If specified, this file will be used as configuration file otherwise default configuration file will be used. spec.arbiter.podTemplate holds the arbiter-podSpec. null value of it, instructs kubedb operator to use the default arbiter podTemplate.
  • spec.terminationPolicy field is Wipeout means that the database will be deleted without restrictions. It can also be “Halt”, “Delete” and “DoNotTerminate”. Learn More about these checkout Termination Policy .

Once these are handled correctly and the MongoDB object is deployed, you will see that the following objects are created:

$ kubectl get all -n demo
NAME                    READY   STATUS    RESTARTS   AGE
pod/mongodb-0           2/2     Running   0          4m34s
pod/mongodb-1           2/2     Running   0          3m32s
pod/mongodb-arbiter-0   1/1     Running   0          2m39s

NAME                   TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)     AGE
service/mongodb        ClusterIP   <none>        27017/TCP   4m36s
service/mongodb-pods   ClusterIP   None          <none>        27017/TCP   4m36s

NAME                               READY   AGE
statefulset.apps/mongodb           2/2     4m36s
statefulset.apps/mongodb-arbiter   1/1     2m41s

NAME                                         TYPE                 VERSION   AGE   6.0.5     2m6s

NAME                         VERSION   STATUS   AGE   6.0.5     Ready    4m42s

Let’s check if the database is ready to use,

$ kubectl get mongodb -n demo mongodb
mongodb   6.0.5     Ready    5m35s

We have successfully deployed MongoDB ReplicaSet with Arbiter in GKE. Now we can exec into the container to use the database.

Accessing Database Through CLI

To access the database through CLI, we have to get the credentials to access. KubeDB will create Secret and Service for the database mongodb that we have deployed. Let’s check them using the following commands,

$ kubectl get secret -n demo
NAME           TYPE                       DATA   AGE
mongodb-auth   2      6m48s
mongodb-key    Opaque                     1      6m48s

$ kubectl get service -n demo
NAME           TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)     AGE
mongodb        ClusterIP   <none>        27017/TCP   7m20s
mongodb-pods   ClusterIP   None          <none>        27017/TCP   7m20s

Now, we are going to use mongodb-auth to get the credentials.

$ kubectl get secrets -n demo mongodb-auth -o jsonpath='{.data.\username}' | base64 -d

$ kubectl get secrets -n demo mongodb-auth -o jsonpath='{.data.\password}' | base64 -d

Insert Sample Data

In this section, we are going to login into our MongoDB and insert some sample data.

$ kubectl exec -it mongodb-0 -n demo bash
root@mongodb-0:/# mongosh admin -u root -p 'iyyur*0O4U~.wd*q'
Using MongoDB:		6.0.5
Using Mongosh:		1.8.2

rs0 [direct: primary] admin> rs.status()
  set: 'rs0',
  date: ISODate("2023-08-08T11:49:11.657Z"),
  myState: 1,
  term: Long("1"),
  syncSourceHost: '',
  syncSourceId: -1,
  heartbeatIntervalMillis: Long("2000"),
  majorityVoteCount: 2,
  writeMajorityCount: 2,
  votingMembersCount: 3,
  writableVotingMembersCount: 2,
  optimes: {
    lastCommittedOpTime: { ts: Timestamp({ t: 1691495350, i: 1 }), t: Long("1") },
    lastCommittedWallTime: ISODate("2023-08-08T11:49:10.964Z"),
    readConcernMajorityOpTime: { ts: Timestamp({ t: 1691495350, i: 1 }), t: Long("1") },
    appliedOpTime: { ts: Timestamp({ t: 1691495350, i: 1 }), t: Long("1") },
    durableOpTime: { ts: Timestamp({ t: 1691495350, i: 1 }), t: Long("1") },
    lastAppliedWallTime: ISODate("2023-08-08T11:49:10.964Z"),
    lastDurableWallTime: ISODate("2023-08-08T11:49:10.964Z")
  lastStableRecoveryTimestamp: Timestamp({ t: 1691495310, i: 1 }),
  electionCandidateMetrics: {
    lastElectionReason: 'electionTimeout',
    lastElectionDate: ISODate("2023-08-08T11:36:30.834Z"),
    electionTerm: Long("1"),
    lastCommittedOpTimeAtElection: { ts: Timestamp({ t: 1691494590, i: 1 }), t: Long("-1") },
    lastSeenOpTimeAtElection: { ts: Timestamp({ t: 1691494590, i: 1 }), t: Long("-1") },
    numVotesNeeded: 1,
    priorityAtElection: 1,
    electionTimeoutMillis: Long("10000"),
    newTermStartDate: ISODate("2023-08-08T11:36:30.897Z"),
    wMajorityWriteAvailabilityDate: ISODate("2023-08-08T11:36:30.928Z")
  members: [
      _id: 0,
      name: 'mongodb-0.mongodb-pods.demo.svc.cluster.local:27017',
      health: 1,
      state: 1,
      stateStr: 'PRIMARY',
      uptime: 778,
      optime: { ts: Timestamp({ t: 1691495350, i: 1 }), t: Long("1") },
      optimeDate: ISODate("2023-08-08T11:49:10.000Z"),
      lastAppliedWallTime: ISODate("2023-08-08T11:49:10.964Z"),
      lastDurableWallTime: ISODate("2023-08-08T11:49:10.964Z"),
      syncSourceHost: '',
      syncSourceId: -1,
      infoMessage: '',
      electionTime: Timestamp({ t: 1691494590, i: 2 }),
      electionDate: ISODate("2023-08-08T11:36:30.000Z"),
      configVersion: 4,
      configTerm: 1,
      self: true,
      lastHeartbeatMessage: ''
      _id: 1,
      name: 'mongodb-1.mongodb-pods.demo.svc.cluster.local:27017',
      health: 1,
      state: 2,
      stateStr: 'SECONDARY',
      uptime: 713,
      optime: { ts: Timestamp({ t: 1691495340, i: 1 }), t: Long("1") },
      optimeDurable: { ts: Timestamp({ t: 1691495340, i: 1 }), t: Long("1") },
      optimeDate: ISODate("2023-08-08T11:49:00.000Z"),
      optimeDurableDate: ISODate("2023-08-08T11:49:00.000Z"),
      lastAppliedWallTime: ISODate("2023-08-08T11:49:10.964Z"),
      lastDurableWallTime: ISODate("2023-08-08T11:49:10.964Z"),
      lastHeartbeat: ISODate("2023-08-08T11:49:10.752Z"),
      lastHeartbeatRecv: ISODate("2023-08-08T11:49:10.818Z"),
      pingMs: Long("0"),
      lastHeartbeatMessage: '',
      syncSourceHost: 'mongodb-0.mongodb-pods.demo.svc.cluster.local:27017',
      syncSourceId: 0,
      infoMessage: '',
      configVersion: 4,
      configTerm: 1
      _id: 2,
      name: 'mongodb-arbiter-0.mongodb-pods.demo.svc.cluster.local:27017',
      health: 1,
      state: 7,
      stateStr: 'ARBITER',
      uptime: 671,
      lastHeartbeat: ISODate("2023-08-08T11:49:10.739Z"),
      lastHeartbeatRecv: ISODate("2023-08-08T11:49:10.901Z"),
      pingMs: Long("0"),
      lastHeartbeatMessage: '',
      syncSourceHost: '',
      syncSourceId: -1,
      infoMessage: '',
      configVersion: 4,
      configTerm: 1
  ok: 1,
  '$clusterTime': {
    clusterTime: Timestamp({ t: 1691495350, i: 1 }),
    signature: {
      hash: Binary(Buffer.from("aab31f7bd957f882a17c0c6e0499c8132388ec40", "hex"), 0),
      keyId: Long("7264913945410928646")
  operationTime: Timestamp({ t: 1691495350, i: 1 })

Here you can see the arbiter pod in the members list of rs.status() output.

rs0 [direct: primary] admin> rs.isMaster().primary
rs0 [direct: primary] admin> show dbs
admin          172.00 KiB
config         384.00 KiB
kubedb-system   40.00 KiB
local          484.00 KiB
rs0 [direct: primary] admin> show users
    _id: 'admin.root',
    userId: new UUID("da00afbb-8253-4c06-a0a3-73da9150c5df"),
    user: 'root',
    db: 'admin',
    roles: [ { role: 'root', db: 'admin' } ],
    mechanisms: [ 'SCRAM-SHA-1', 'SCRAM-SHA-256' ]
rs0 [direct: primary] admin> use musicdb
switched to db musicdb
rs0 [direct: primary] musicdb> db.songs.insert({"name":"Take Me Home, Country Roads"});
DeprecationWarning: Collection.insert() is deprecated. Use insertOne, insertMany, or bulkWrite.
  acknowledged: true,
  insertedIds: { '0': ObjectId("64d22dc726e92e668599395a") }
rs0 [direct: primary] musicdb> exit

We’ve successfully inserted some sample data to our MongoDB database. More information about Run & Manage MongoDB on Kubernetes can be found Kubernetes MongoDB

Now, To check the data availability to the secondary members we’ll now exec into mongodb-1 pod (which is secondary member right now).

$ kubectl exec -it mongodb-1 -n demo bash
root@mongodb-1:/# mongosh admin -u root -p 'iyyur*0O4U~.wd*q'
Using MongoDB:		6.0.5
Using Mongosh:		1.8.2

rs0 [direct: secondary] admin> rs.secondaryOk()
DeprecationWarning: .setSecondaryOk() is deprecated. Use .setReadPref("primaryPreferred") instead
Setting read preference from "primary" to "primaryPreferred"

rs0 [direct: secondary] admin> show users
    _id: 'admin.root',
    userId: new UUID("da00afbb-8253-4c06-a0a3-73da9150c5df"),
    user: 'root',
    db: 'admin',
    roles: [ { role: 'root', db: 'admin' } ],
    mechanisms: [ 'SCRAM-SHA-1', 'SCRAM-SHA-256' ]
rs0 [direct: secondary] admin> use musicdb
switched to db musicdb
rs0 [direct: secondary] musicdb> db.songs.find().pretty()
    _id: ObjectId("64d22dc726e92e668599395a"),
    name: 'Take Me Home, Country Roads'
rs0 [direct: secondary] musicdb> exit

we’ve successfully access the data in mongodb-1. So, the data is available to the secondary members.

If you want to learn more about Production-Grade MongoDB you can have a look into that playlist below:


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More about MongoDB in Kubernetes

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