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Deploy a Replica Set

Cloud Manager and Ops Manager 4.0.11 Support MongoDB Resources

You can use the Kubernetes Operator to deploy MongoDB resources with Ops Manager version 4.0.11 or later and Cloud Manager. At any place in this guide that says Ops Manager, you can substitute Cloud Manager.

A replica set is a group of MongoDB deployments that maintain the same data set. Replica sets provide redundancy and high availability and are the basis for all production deployments.

To learn more about replica sets, see the Replication Introduction in the MongoDB manual.

Use this procedure to deploy a new replica set that Ops Manager manages. After deployment, use Ops Manager to manage the replica set, including such operations as adding, removing, and reconfiguring members.

Prerequisites

To deploy a replica set using an object, you need to complete the following procedures:

Considerations

Starting in MongoDB Enterprise Kubernetes Operator version 1.3.0, you can only have one MongoDB resource per project. To learn how to migrate your project to a single-cluster configuration, see Migrate to One Resource per Project (Required for Version 1.3.0).

Deploy a Replica Set

1

Configure kubectl to default to your namespace.

If you have not already, run the following command to execute all kubectl commands in the namespace you created:

kubectl config set-context $(kubectl config current-context) --namespace=<namespace>
2

Copy the highlighted section of this replica set resource.

Change the highlighted settings of this YAML file to match your desired replica set configuration.

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---
apiVersion: mongodb.com/v1
kind: MongoDB
metadata:
  name: <my-replica-set>
spec:
  members: 3
  version: 4.2.2-ent
  opsManager:
    configMapRef:
      name: <configMap.metadata.name>
            # Must match metadata.name in ConfigMap file
  credentials: <mycredentials>
  type: ReplicaSet
  persistent: true
...
3

Paste the copied example to create a new replica set resource.

Open your preferred text editor and paste the object specification into a new text file.

4

Change the highlighted settings to your preferred values.

Key Type Description Example
metadata.name string

Label for this Kubernetes replica set object.

Resource names must be 44 characters or less.

See also

myproject
spec.members integer Number of members of the replica set. 3
spec.version string

Version of MongoDB that this replica set should run.

The format should be X.Y.Z for the Community edition and X.Y.Z-ent for the Enterprise edition.

Important

Ensure that you choose a compatible MongoDB Server version.

Compatible versions differ depending on the base image that the MongoDB database resource uses.

To learn more about MongoDB versioning, see MongoDB Versioning in the MongoDB Manual.

3.6.7
spec
.opsManager
.configMapRef
string

Name of the ConfigMap with the Ops Manager connection configuration. The spec.cloudManager.configMapRef.name setting is an alias for this setting and can be used in its place.

Value must match namespace and name of ConfigMap

This value must match the namespace in which you created the Ops Manager project ConfigMap.

Operator manages changes to the ConfigMap

The Kubernetes Operator tracks any changes to the ConfigMap and reconciles the state of the MongoDB Kubernetes resource.

<myconfigmap>
spec.credentials string

Name of the Kubernetes secret you created as Ops Manager API authentication credentials for the Kubernetes Operator to communicate with Ops Manager.

Value must use namespace and name of Secret

This value must match the namespace in which you created the secret and the name value you provided for your Ops Manager Kubernetes Secret.

Operator manages changes to the Secret

The Kubernetes Operator tracks any changes to the Secret and reconciles the state of the MongoDB Kubernetes resource.

<mycredentials>
spec.type string Type of MongoDB Kubernetes resource to create. ReplicaSet
spec.persistent string

Optional.

Flag indicating if this MongoDB Kubernetes resource should use Persistent Volumes for storage. Persistent volumes are not deleted when the MongoDB Kubernetes resource is stopped or restarted.

If this value is true, then spec.podSpec.persistence.single is set to its default value of 16Gi.

To change your Persistent Volume Claims configuration, configure the following collections to meet your deployment requirements:

Warning

Your containers must have permissions to write to your Persistent Volume. The Kubernetes Operator sets fsGroup = 2000 in securityContext This makes Kubernetes try to fix write permissions for the Persistent Volume. If redeploying the deployment item does not fix issues with your Persistent Volumes, contact MongoDB Support.

Note

If you do not use Persistent Volumes, the Disk Usage and Disk IOPS charts cannot be displayed in either the Processes tab on the Deployment page or in the Metrics page when reviewing the data for this deployment.

true
5

Add any additional accepted settings for a replica set deployment.

You can also add any of the following optional settings to the object specification file for a replica set deployment:

Warning

You must set spec.clusterDomain if your Kubernetes cluster has a default domain other than the default cluster.local. If you neither use the default nor set the spec.clusterDomain option, the Kubernetes Operator might not function as expected.

6

Save this replica set config file with a .yaml file extension.

7

Start your replica set deployment.

Invoke the following Kubernetes command to create your replica set:

kubectl apply -f <replica-set-conf>.yaml
8

Track the status of your replica set deployment.

To check the status of your MongoDB Kubernetes resource, invoke the following command:

kubectl get mdb <resource-name> -o yaml -w

The -w flag means “watch”. With the “watch” flag set, the output refreshes immediately when something changes until the status phase achieves the Running state.

See Troubleshooting the Kubernetes Operator for information about the resource deployment statuses.

Enable External Access for a Replica Set

1

Optional: Deploy a replica set with the Kubernetes Operator.

If you haven’t deployed a replica set, follow the instructions to deploy one.

To simplify the configuration, don’t enable TLS with the spec.security.tls.enabled setting.

2

Optional: Add Subject Alternate Names to your TLS certificates.

If the Kubernetes Operator deployed a TLS-enabled replica set, provide the external DNS names (SANs) for each member.

3

Create a NodePort for each pod.

Invoke the following commands to create the NodePorts:

kubectl expose pod/<my-replica-set>-0 --type="NodePort" --port 27017
kubectl expose pod/<my-replica-set>-1 --type="NodePort" --port 27017
kubectl expose pod/<my-replica-set>-2 --type="NodePort" --port 27017
4

Discover the dynamically assigned NodePorts.

Discover the dynamically assigned NodePorts:

$ kubectl get svc | grep <my-replica-set>
<my-replica-set>-0     NodePort   172.30.39.228   <none>  27017:30907/TCP  16m
<my-replica-set>-1     NodePort   172.30.185.136  <none>  27017:32350/TCP  16m
<my-replica-set>-2     NodePort   172.30.84.192   <none>  27017:31185/TCP  17m
<my-replica-set>-svc   ClusterIP  None            <none>  27017/TCP        38m

NodePorts range from 30000 to 32767, inclusive.

5

Open your replica set resource YAML file.

6

Copy the highlighted section of this replica set resource.

Change the highlighted settings of this YAML file to match your desired replica set configuration.

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---
apiVersion: mongodb.com/v1
kind: MongoDB
metadata:
  name: <my-replica-set>
spec:
  members: 3
  version: 4.2.2-ent
  type: ReplicaSet
  opsManager:
    configMapRef:
      name: <configMap.metadata.name>
  credentials: <mycredentials>
  persistent: true
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  security:
    tls:
      enabled: true
  connectivity:
    replicaSetHorizons:
      - "example-website": "web1.example.com:10017"
      - "example-website": "web2.example.com:10017"
      - "example-website": "web3.example.com:10017"
...
7

Paste the copied example section into your existing replica set resource.

Open your preferred text editor and paste the object specification at the end of your resource file in the spec section.

8

Change the highlighted settings to your preferred values.

Key Type Necessity Description Example
spec.security.tls
boolean Optional

Set this value to true to enable TLS on the MongoDB deployment.

By default, Kubernetes Operator requires hosts to use and accept TLS encrypted connections.

Note

To connect to a replica set from outside Kubernetes, set this value to true.

true
spec.connectivity
collection Conditional

Add this parameter and values if you need your database to be accessed outside of Kubernetes. This setting allows you to provide different DNS settings within the Kubernetes cluster and to the Kubernetes cluster. The Kubernetes Operator uses split horizon DNS for replica set members. This feature allows communication both within the Kubernetes cluster and from outside Kubernetes.

You may add multiple external mappings per host.

Split Horizon Requirements

  • Make sure that each value in this array is unique.
  • Make sure that the number of entries in this array matches the value given in spec.members.
  • Set the spec.security.tls.enabled to true to enable TLS. This method to use split horizons requires the Server Name Indication extension of the TLS protocol.
See Setting
9

Confirm the external hostnames and NodePort values in your replica set resource.

Confirm that the external hostnames in the spec.connectivity.replicaSetHorizons setting are correct.

External hostnames should match the DNS names of Kubernetes worker nodes. These can be any nodes in the Kubernetes cluster. nodes do internal routing if the pod is run on another node.

Set the ports in spec.connectivity.replicaSetHorizons to the NodePort values that you discovered.

Example

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  security:
    tls:
      enabled: true
  connectivity:
    replicaSetHorizons:
      - "example-website": "web1.example.com:30907"
      - "example-website": "web2.example.com:32350"
      - "example-website": "web3.example.com:31185"
...
10

Save your replica set config file.

11

Update and restart your replica set deployment.

Invoke the following Kubernetes command to update and restart your replica set:

kubectl apply -f <replica-set-conf>.yaml
12

Test the connection to the replica set.

mongo --host <my-replica-set>/web1.example.com:30907,web2.example.com:32350,web3.example.com:31185 \
      --ssl \
      --sslAllowInvalidCertificates

Warning

Don’t use the --sslAllowInvalidCertificates flag in production. In production, share the Kubernetes CA files with client tools or applications.

If the connection succeeds, you should see:

MongoDB Enterprise <my-replica-set>:PRIMARY