Architecture, Capabilities, and Limitations¶

Connect with DNS SRV Records¶

To connect to the multi-Kubernetes-cluster deployment database as a user, you can use the connectionString.standardSrv: DNS seed list connection string. This string is included in the secret that the Kubernetes Operator creates for your multi-Kubernetes-cluster deployment. Use the same procedure for connecting to the multi-Kubernetes-cluster deployment as for single clusters deployed with Kubernetes Operator. See Connect to a MongoDB Database Resource from Inside Kubernetes and select the tab Using the Kubernetes Secret.

Manage Security for Database Users¶

Use these methods to manage security for database users:

• LDAP authentication
• SCRAM authentication
• TLS and X.509 for internal cluster authentication

These procedures are the same as the procedures for single clusters deployed with the Kubernetes Operator, with the following exceptions:

• The procedures apply to replica sets only. Multi-Kubernetes-cluster deployments don’t support creating sharded clusters.
• In the mongodbResourceRef, specify the name of the multi-Kubernetes-cluster deployment replica set: name: "<my-multi-cluster-replica-set>".

Deploy an Ops Manager Resource on the Central Cluster and Connect to Ops Manager¶

To deploy an Ops Manager instance in the central cluster and connect to it, use the following procedures:

• Review the Ops Manager resource architecture
• Review the Ops Manager resource considerations and prerequisites
• Deploy an Ops Manager instance on the central cluster with TLS encryption

These procedures are the same as the procedures for single clusters deployed with the Kubernetes Operator with the following exceptions:

• Run the procedures to deploy Ops Manager only on the central cluster of your multi-Kubernetes-cluster deployment.

• Set the context and the namespace.

  If you are deploying an Ops Manager resource on a multi-Kubernetes-cluster deployment:

  • Set the context to the name of the central cluster, such as: kubectl config set context "$MDB_CENTRAL_CLUSTER_FULL_NAME".
  • Set the --namespace to the same scope that you used for your multi-Kubernetes-cluster deployment, such as: kubectl config --namespace "mongodb".

• Configure external connectivity for Ops Manager.

  To connect member clusters to the Ops Manager resource’s deployment in the central cluster in a multi-Kubernetes-cluster deployment, use one of the following methods:

  • Set the spec.externalConnectivity to true and specify the Ops Manager port in it. Use the ops-manager-external.yaml example script, modify it to your needs, and apply the configuration. For example, run:

    copy

    kubectl apply \
     --context "$MDB_CENTRAL_CLUSTER_FULL_NAME" \
     --namespace "mongodb" \
      -f https://raw.githubusercontent.com/mongodb/mongodb-enterprise-kubernetes/master/samples/ops-manager/ops-manager-external.yaml
    

  • Add the central cluster and all member clusters to the service mesh. The service mesh establishes communication from the central and all member clusters to the Ops Manager instance. To learn more, see the Multi-Kubernetes-Cluster Quick Start procedures and see the step that references the istio-injection=enabled label for Istio. Also, see Automatic sidecar injection in the Istio documentation.

Set up Queryable Backups for Ops Manager Resources¶

If you deploy Ops Manager with the Kubernetes Operator, the central cluster may also host Ops Manager. In this case, you can configure queryable backups for Ops Manager resources.

Diagram: Multi-Kubernetes Cluster Deployment with a Service Mesh¶

The following diagram shows the high-level architecture of a multi-Kubernetes-cluster deployment across regions and availability zones. This deployment uses a service mesh, such as Istio. The service mesh:

• Manages the discovery of MongoDB nodes deployed in different Kubernetes member clusters.
• Handles communication between replica set members.

You can host your application on any of the member clusters inside the service mesh, such as:

• On Kubernetes clusters outside of the ones that you deploy with the Kubernetes Operator, or
• On the member clusters in a multi-Kubernetes-cluster deployment.

Diagram: Multi-Kubernetes Cluster Deployment without a Service Mesh¶

The following diagram shows the high-level architecture of a multi-Kubernetes-cluster deployment across regions and availability zones. This deployment doesn’t rely on a service mesh for connectivity between the Kubernetes clusters hosting Pods with MongoDB instances.

To handle external communication between MongoDB replica set members hosted on Pods in distinct Kubernetes clusters, use external domains and DNS zones.

You can host your application on any of the member clusters.