Multi-Cluster ReplicaSets

Multi-Kubernetes cluster MongoDB deployments allow you to add MongoDB instances in global clusters that span multiple geographic regions for increased availability and global distribution of data.

Prerequisites

Before you begin the following procedure, perform the following actions:

Install kubectl.
Install Mongosh
Complete the GKE Clusters procedure or the equivalent.
Complete the TLS Certificates procedure or the equivalent.
Complete the Istio Service mesh procedure or the equivalent.
Complete the Deploy the MongoDB Operator procedure.
Complete the Multi-Cluster Ops Manager procedure procedure. You can skip this step if you use Cloud Manager instead of Ops Manager.
Set the required environment variables as follows:

# This script builds on top of the environment configured in the setup guides.
# It depends (uses) the following env variables defined there to work correctly.
# If you don't use the setup guide to bootstrap the environment, then define them here.
#  ${K8S_CLUSTER_0_CONTEXT_NAME}
#  ${K8S_CLUSTER_1_CONTEXT_NAME}
#  ${K8S_CLUSTER_2_CONTEXT_NAME}
#  ${MDB_NAMESPACE}
export RS_RESOURCE_NAME=mdb
export MONGODB_VERSION="8.0.5-ent"

Source Code

You can find all included source code in the MongoDB Kubernetes Operator repository.

Procedure

Create a CA certificate.

Run the following script to create the required CA Certificate with your certificate issuer.

1 kubectl apply --context "${K8S_CLUSTER_0_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" -f - <<EOF
2 apiVersion: cert-manager.io/v1
3 kind: Certificate
4 metadata:
5   name: mdb-cert
6 spec:
7   dnsNames:
8   - "*.${MDB_NAMESPACE}.svc.cluster.local"
9   duration: 240h0m0s
10   issuerRef:
11     name: my-ca-issuer
12     kind: ClusterIssuer
13   renewBefore: 120h0m0s
14   secretName: cert-prefix-mdb-cert
15   usages:
16   - server auth
17   - client auth
18 EOF

Deploy the `MongoDBMultiCluster` resource.

Set spec.credentials, spec.opsManager.configMapRef.name, which you defined in the Multi-Cluster Ops Manager procedure; define your security settings and deploy the MongoDBMultiCluster resource. In the following code sample, duplicateServiceObjects is set to false to enable DNS proxying in Istio.

Note

To enable the cross-cluster DNS resolution by the Istio service mesh, this tutorial creates service objects with a single ClusterIP address per each Kubernetes Pod.

1 kubectl apply --context "${K8S_CLUSTER_0_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" -f - <<EOF
2 apiVersion: mongodb.com/v1
3 kind: MongoDBMultiCluster
4 metadata:
5   name: ${RS_RESOURCE_NAME}
6 spec:
7   type: ReplicaSet
8   version: ${MONGODB_VERSION}
9   opsManager:
10     configMapRef:
11       name: mdb-org-project-config
12   credentials: mdb-org-owner-credentials
13   duplicateServiceObjects: false
14   persistent: true
15   backup:
16     mode: enabled
17   externalAccess: {}
18   security:
19     certsSecretPrefix: cert-prefix
20     tls:
21       ca: ca-issuer
22     authentication:
23       enabled: true
24       modes: ["SCRAM"]
25   clusterSpecList:
26     - clusterName: ${K8S_CLUSTER_0_CONTEXT_NAME}
27       members: 2
28     - clusterName: ${K8S_CLUSTER_1_CONTEXT_NAME}
29       members: 1
30     - clusterName: ${K8S_CLUSTER_2_CONTEXT_NAME}
31       members: 2
32 EOF

Verify that the `MongoDBMultiCluster` resource is running.

Run the following command to confirm that the MongoDBMultiCluster resource is running.

1 echo; echo "Waiting for MongoDB to reach Running phase..."
2 kubectl --context "${K8S_CLUSTER_0_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" wait --for=jsonpath='{.status.phase}'=Running "mdbmc/${RS_RESOURCE_NAME}" --timeout=900s
3 echo; echo "Pods running in cluster ${K8S_CLUSTER_0_CONTEXT_NAME}"
4 kubectl --context "${K8S_CLUSTER_0_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" get pods
5 echo; echo "Pods running in cluster ${K8S_CLUSTER_1_CONTEXT_NAME}"
6 kubectl --context "${K8S_CLUSTER_1_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" get pods
7 echo; echo "Pods running in cluster ${K8S_CLUSTER_2_CONTEXT_NAME}"
8 kubectl --context "${K8S_CLUSTER_2_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" get pods

Create a MongoDB user and password.

Run the following command to create a MongoDB user and password. Please use strong passwords for your deployments.

1 kubectl apply --context "${K8S_CLUSTER_0_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" -f - <<EOF
2 apiVersion: v1
3 kind: Secret
4 metadata:
5   name: rs-user-password
6 type: Opaque
7 stringData:
8   password: password
9 ---
10 apiVersion: mongodb.com/v1
11 kind: MongoDBUser
12 metadata:
13   name: rs-user
14 spec:
15   passwordSecretKeyRef:
16     name: rs-user-password
17     key: password
18   username: "rs-user"
19   db: "admin"
20   mongodbResourceRef:
21     name: ${RS_RESOURCE_NAME}
22   roles:
23   - db: "admin"
24     name: "root"
25 EOF
26 
27 kubectl --context "${K8S_CLUSTER_0_CONTEXT_NAME}" wait --for=jsonpath='{.status.phase}'=Updated -n "${MDB_NAMESPACE}" mdbu/rs-user --timeout=300s

Verify connectivity.

Run the mongosh following command to ensure that you can access your running MongoDB instance.

1 external_ip="$(kubectl get --context "${K8S_CLUSTER_0_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" svc "${RS_RESOURCE_NAME}-0-0-svc-external" -o=jsonpath="{.status.loadBalancer.ingress[0].ip}")"
2 
3 mkdir -p certs
4 kubectl get --context "${K8S_CLUSTER_0_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" cm/ca-issuer -o=jsonpath='{.data.ca-pem}' > certs/ca.crt
5 
6 mongosh --host "${external_ip}" --username rs-user --password password --tls --tlsCAFile certs/ca.crt --tlsAllowInvalidHostnames --eval "db.runCommand({connectionStatus : 1})"

{
  authInfo: {
    authenticatedUsers: [ { user: 'rs-user', db: 'admin' } ],
    authenticatedUserRoles: [ { role: 'root', db: 'admin' } ]
  },
  ok: 1,
  '$clusterTime': {
    clusterTime: Timestamp({ t: 1747925179, i: 1 }),
    signature: {
      hash: Binary.createFromBase64('T1ZP+QUFgBXayfOsRI6XFdEmjKI=', 0),
      keyId: Long('7507281432415305733')
    }
  },
  operationTime: Timestamp({ t: 1747925179, i: 1 })
}

Back

Multi-Cluster Ops Manager

Multi-Cluster Sharded Cluster

1	kubectl apply --context "${K8S_CLUSTER_0_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" -f - <<EOF
2	apiVersion: cert-manager.io/v1
3	kind: Certificate
4	metadata:
5	name: mdb-cert
6	spec:
7	dnsNames:
8	- "*.${MDB_NAMESPACE}.svc.cluster.local"
9	duration: 240h0m0s
10	issuerRef:
11	name: my-ca-issuer
12	kind: ClusterIssuer
13	renewBefore: 120h0m0s
14	secretName: cert-prefix-mdb-cert
15	usages:
16	- server auth
17	- client auth
18	EOF

1	kubectl apply --context "${K8S_CLUSTER_0_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" -f - <<EOF
2	apiVersion: mongodb.com/v1
3	kind: MongoDBMultiCluster
4	metadata:
5	name: ${RS_RESOURCE_NAME}
6	spec:
7	type: ReplicaSet
8	version: ${MONGODB_VERSION}
9	opsManager:
10	configMapRef:
11	name: mdb-org-project-config
12	credentials: mdb-org-owner-credentials
13	duplicateServiceObjects: false
14	persistent: true
15	backup:
16	mode: enabled
17	externalAccess: {}
18	security:
19	certsSecretPrefix: cert-prefix
20	tls:
21	ca: ca-issuer
22	authentication:
23	enabled: true
24	modes: ["SCRAM"]
25	clusterSpecList:
26	- clusterName: ${K8S_CLUSTER_0_CONTEXT_NAME}
27	members: 2
28	- clusterName: ${K8S_CLUSTER_1_CONTEXT_NAME}
29	members: 1
30	- clusterName: ${K8S_CLUSTER_2_CONTEXT_NAME}
31	members: 2
32	EOF

1	echo; echo "Waiting for MongoDB to reach Running phase..."
2	kubectl --context "${K8S_CLUSTER_0_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" wait --for=jsonpath='{.status.phase}'=Running "mdbmc/${RS_RESOURCE_NAME}" --timeout=900s
3	echo; echo "Pods running in cluster ${K8S_CLUSTER_0_CONTEXT_NAME}"
4	kubectl --context "${K8S_CLUSTER_0_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" get pods
5	echo; echo "Pods running in cluster ${K8S_CLUSTER_1_CONTEXT_NAME}"
6	kubectl --context "${K8S_CLUSTER_1_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" get pods
7	echo; echo "Pods running in cluster ${K8S_CLUSTER_2_CONTEXT_NAME}"
8	kubectl --context "${K8S_CLUSTER_2_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" get pods

1	kubectl apply --context "${K8S_CLUSTER_0_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" -f - <<EOF
2	apiVersion: v1
3	kind: Secret
4	metadata:
5	name: rs-user-password
6	type: Opaque
7	stringData:
8	password: password
9	---
10	apiVersion: mongodb.com/v1
11	kind: MongoDBUser
12	metadata:
13	name: rs-user
14	spec:
15	passwordSecretKeyRef:
16	name: rs-user-password
17	key: password
18	username: "rs-user"
19	db: "admin"
20	mongodbResourceRef:
21	name: ${RS_RESOURCE_NAME}
22	roles:
23	- db: "admin"
24	name: "root"
25	EOF
26
27	kubectl --context "${K8S_CLUSTER_0_CONTEXT_NAME}" wait --for=jsonpath='{.status.phase}'=Updated -n "${MDB_NAMESPACE}" mdbu/rs-user --timeout=300s

1	external_ip="$(kubectl get --context "${K8S_CLUSTER_0_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" svc "${RS_RESOURCE_NAME}-0-0-svc-external" -o=jsonpath="{.status.loadBalancer.ingress[0].ip}")"
2
3	mkdir -p certs
4	kubectl get --context "${K8S_CLUSTER_0_CONTEXT_NAME}" -n "${MDB_NAMESPACE}" cm/ca-issuer -o=jsonpath='{.data.ca-pem}' > certs/ca.crt
5
6	mongosh --host "${external_ip}" --username rs-user --password password --tls --tlsCAFile certs/ca.crt --tlsAllowInvalidHostnames --eval "db.runCommand({connectionStatus : 1})"