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Connect to Multi-Cluster Resource from Outside Kubernetes

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  • Prerequisite
  • Considerations
  • Procedure

The following procedure describes how to connect to a MongoDBMultiCluster resource deployed in Kubernetes from outside of the Kubernetes cluster.

Databases that run MongoDB 4.2.3 or later allow you to access them outside of the Kubernetes cluster.

If you create custom services that require external access to MongoDB custom resources deployed by the Kubernetes Operator and use readiness probes in Kubernetes, set the publishNotReadyAddresses setting in Kubernetes to true.

The publishNotReadyAddresses setting indicates that an agent that interacts with endpoints for this service should disregard the service's ready state. Setting publishNotReadyAddresses to true overrides the behavior of the readiness probe configured for the Pod hosting your service.

By default, the publishNotReadyAddresses setting is set to false. In this case, when the Pods that host the MongoDB custom resources in the Kubernetes Operator lose connectivity to Cloud Manager or Ops Manager, the readiness probes configured for these Pods fail. However, when you set the publishNotReadyAddresses setting to true:

  • Kubernetes does not shut down the service whose readiness probe fails.

  • Kubernetes considers all endpoints as ready even if the probes for the Pods hosting the services for these endpoints indicate that they aren't ready.

  • MongoDB custom resources are still available for read and write operations.

Tip

See also:

To connect to your Kubernetes Operator-deployed replica set with a MongoDBMultiCluster resource from outside of the Kubernetes cluster:

1
2

Provide values for:

  • The TLS secret in spec.security.certsSecretPrefix.

  • The custom CA certificate in spec.security.tls.ca.

3

To connect to your multi-Kubernetes-cluster deployment from an external resource, configure the spec.externalAccess setting:

externalAccess: {}

This setting instructs the Kubernetes Operator to create an external LoadBalancer service for the MongoDB Pods in your multi-Kubernetes-cluster deployment. The external service provides an entry point for external connections. Adding this setting with no values creates an external service with the following default values:

Field
Value
Description
Name
<pod-name>-svc-external
Name of the external service. You can't change this value.
Type
LoadBalancer
Creates an external LoadBalancer service.
Port
<Port Number>
A port for mongod.
publishNotReadyAddress
true
Specifies that DNS records are created even if the Pod isn't ready. Do not set to false for any database Pod.

Optionally, if you need to add values to the service or override the default values, specify:

For example, the following settings override the default values for the external service to configure your multi-Kubernetes-cluster deployment to create NodePort services that expose the MongoDB Pods:

externalAccess:
externalService:
annotations:
# cloud-specific annotations for the service
spec:
type: NodePort # default is LoadBalancer
port: 27017
# you can specify other spec overrides if necessary

Tip

To learn more, see annotations and ServiceSpec in the Kubernetes documentation.

4

If you need to configure settings for a specific cluster member, such as when you're hosting members on different cloud providers, you can override the global spec.externalAccess settings for a specific member by using the spec.clusterSpecList.externalAccess.externalService setting.

To add values to the service or override the default values for a cluster member, specify:

For example, the following file configures your multi-Kubernetes cluster MongoDB deployment to create load balancer services that expose the multi-Kubernetes cluster MongoDB deployment for cluster members deployed in GKE (Google Kubernetes Engine) and AWS EKS.

Note

The following example doesn't configure overrides, so the external services use the default values from the spec.externalAccess setting.

clusterSpecList:
- clusterName: gke-cluster-0.mongokubernetes.com
members: 2
externalAccess:
externalService:
annotations:
"cloud.google.com/l4-rbs": "enabled"
- clusterName: eks-cluster-1.mongokubernetes.com
members: 2
externalAccess:
externalService:
annotations:
"service.beta.kubernetes.io/aws-load-balancer-type": "external",
"service.beta.kubernetes.io/aws-load-balancer-nlb-target-type": "instance",
"service.beta.kubernetes.io/aws-load-balancer-scheme": "internet-facing"
5

Add each external DNS name to the certificate SAN.

6

In each cluster, run the following command to verify that the Kubernetes Operator created the external service for your deployment.

$ kubectl get services

The command returns a list of services similar to the following output. For each database Pod in the cluster, the Kubernetes Operator creates an external service named <pod-name>-<cluster-idx>-<pod-idx>-svc-external. This service is configured according to the values and overrides you provide in the external service specification.

NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
<my-replica-set>-0-0-svc-external LoadBalancer 10.102.27.116 <lb-ip-or-fqdn> 27017:27017/TCP 8m30s

Depending on your cluster configuration or cloud provider, the IP address of the LoadBalancer service is an externally accessible IP address or FQDN. You can use the IP address or FQDN to route traffic from your external domain.

7

Set the hostnames and ports in spec.connectivity.replicaSetHorizons to the external service values that you created in the previous step.

Confirm that you specified the correct external hostnames. External hostnames should match the DNS names of Kubernetes worker nodes. These can be any nodes in the Kubernetes cluster. If the Pod runs on another node, Kubernetes nodes use internal routing.

apiVersion: mongodb.com/v1
kind: MongoDBMultiCluster
metadata:
name: multi-cluster-replica-set
namespace: mongodb
spec:
clusterSpecList:
- clusterName: e2e.cluster1.example.com
members: 1
- clusterName: e2e.cluster2.example.com
members: 1
- clusterName: e2e.cluster3.example.com
members: 1
connectivity:
replicaSetHorizons:
- sample-horizon: web1.example.com:30907
- sample-horizon: web2.example.com:30907
- sample-horizon: web3.example.com:30907
credentials: my-credentials
duplicateServiceObjects: false
opsManager:
configMapRef:
name: my-project
persistent: true
security:
certsSecretPrefix: clustercert
tls:
ca: ca-issuer
type: ReplicaSet
version: 6.0.0-ent"
8

In each cluster, run this command to apply the updated replica set file:

$ Kubectl apply -f <file_name.yaml>
9

In the development environment, for each host in a replica set, run the following command:

mongosh --host <my-replica-set>/web1.example.com \
--port 30907
--ssl \
--sslAllowInvalidCertificates

Note

Don't use the --sslAllowInvalidCertificates flag in production.

In production, for each host in a replica set, specify the TLS certificate and the CA to securely connect to client tools or applications:

mongosh --host <my-replica-set>/web1.example.com \
--port 30907 \
--tls \
--tlsCertificateKeyFile server.pem \
--tlsCAFile ca-pem

If the connection succeeds, you should see:

Enterprise <my-replica-set> [primary]
← Connect to MongoDB Multi-Kubernetes Cluster Resources