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Connect to a MongoDB Database Resource from Outside Kubernetes

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

Prerequisite

Compatible MongoDB Versions

For your databases to be accessed outside of Kubernetes, they must run one of the following versions of MongoDB:

  • 3.6.17 or later
  • 4.0.15 or later
  • 4.2.3 or later

Procedure

How you connect to a MongoDB resource that the Kubernetes Operator deployed from outside of the Kubernetes cluster depends on the resource.

This procedure uses the following example:

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

To connect to your Kubernetes Operator-deployed MongoDB standalone resource from outside of the Kubernetes cluster:

1

Open your standalone resource YAML file.

2

Copy the highlighted section of this standalone resource.

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

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

Paste the copied example section into your existing standalone resource.

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

4

Change the highlighted settings to your preferred values.

Key Type Necessity Description Example
spec.exposedExternally Boolean Optional Set this value to true to allow external services to connect to the MongoDB deployment. This results in Kubernetes creating a NodePort service. true
5

Save your standalone config file.

6

Update and restart your standalone deployment.

Invoke the following Kubernetes command to update and restart your standalone:

kubectl apply -f <standalone-conf>.yaml
7

Discover the dynamically assigned NodePorts.

Discover the dynamically assigned NodePort:

kubectl get services -n <namespace>

The list output should contain an entry similar to the following:

NAME                      TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)           AGE

<my-standalone>           NodePort    10.102.27.116   <none>        27017:30994/TCP   8m30s
  • Kubernetes exposes mongod on port 27017 within the Kubernetes container.
  • The NodePort service exposes the mongod via port 30994. NodePorts range from 30000 to 32767, inclusive.
8

Test the connection to the standalone.

To connect to your deployment from outside of the Kubernetes cluster, run the mongod command with the external FQDN of a node as the --host flag.

Example

If a node in the Kubernetes cluster has an external FQDN of ec2-54-212-23-143.us-west-2.compute.amazonaws.com, you can connect to this standalone instance from outside of the Kubernetes cluster using the following command:

mongo --host ec2-54-212-23-143.us-west-2.compute.amazonaws.com --port 30994

Tip

To obtain the external DNS of your Kubernetes cluster, you can run the following command:

kubectl describe nodes

This command displays the external DNS in the Addresses.ExternalDNS section of the output.

Alternatively, you can output the external DNS directly by running:

kubectl get nodes -o jsonpath='{ $.items[*].status.addresses[?(@.type=="ExternalDNS")].address }'

Important

This procedure explains the least complicated way to enable external connectivity. Other utilities can be used in production.

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

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 replica set has TLS enabled and uses a custom certificate stored with spec.security.tls.ca, add each external DNS name to the certificate SAN.

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:30907"
      - "example-website": "web2.example.com:32350"
      - "example-website": "web3.example.com:31185"
...
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

This procedure uses the following example:

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---
apiVersion: mongodb.com/v1
kind: MongoDB
metadata:
  name: <my-sharded-cluster>
spec:
  version: 4.2.2-ent
  opsManager:
    configMapRef:
      name: <configMap.metadata.name>
            # Must match metadata.name in ConfigMap file
  shardCount: 2
  mongodsPerShardCount: 3
  mongosCount: 2
  configServerCount: 3
  credentials: my-secret
  type: ShardedCluster
  persistent: true
  exposedExternally: true
...

Enable Direct Access to MongoDB hosts Using Split Horizons and TLS

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

The SAN for each MongoDB hosts corresponds to:

<mdb-resource-name><shard><pod-index>.<external-domain>
<mdb-resource-name><config><pod-index>.<external-domain>
<mdb-resource-name><mongos><pod-index>.<external-domain>

Each TLS certificate requires the FQDN (SAN) that corresponds to the FQDN that this host has outside the Kubernetes cluster.

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---
apiVersion: mongodb.com/v1
kind: MongoDB
metadata:
  name: <my-sharded-cluster>
spec:
  version: 4.2.2-ent
  opsManager:
    configMapRef:
      name: <configMap.metadata.name>
            # Must match metadata.name in ConfigMap file
  shardCount: 2
  mongodsPerShardCount: 3
  mongosCount: 2
  configServerCount: 3
  credentials: my-secret
  type: ShardedCluster
  persistent: true
  exposedExternally: true
  security:
    tls:
      enabled: true
      additionalCertificateDomains:
        - "additional-cert-test.com"
...

To connect to your Kubernetes Operator-deployed MongoDB sharded cluster resource from outside of the Kubernetes cluster:

1

Open your sharded cluster resource YAML file.

2

Copy the highlighted section of this sharded cluster resource.

Change the highlighted settings of this YAML file to match your desired sharded cluster configuration.

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---
apiVersion: mongodb.com/v1
kind: MongoDB
metadata:
  name: <my-sharded-cluster>
spec:
  version: 4.2.2-ent
  opsManager:
    configMapRef:
      name: <configMap.metadata.name>
            # Must match metadata.name in ConfigMap file
  shardCount: 2
  mongodsPerShardCount: 3
  mongosCount: 2
  configServerCount: 3
  credentials: my-secret
  type: ShardedCluster
  persistent: true
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  exposedExternally: true
...
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---
apiVersion: mongodb.com/v1
kind: MongoDB
metadata:
  name: <my-sharded-cluster>
spec:
  version: 4.2.2-ent
  opsManager:
    configMapRef:
      name: <configMap.metadata.name>
            # Must match metadata.name in ConfigMap file
  shardCount: 2
  mongodsPerShardCount: 3
  mongosCount: 2
  configServerCount: 3
  credentials: my-secret
  type: ShardedCluster
  persistent: true
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  exposedExternally: true
  security:
    tls:
      enabled: true
      additionalCertificateDomains:
        - "additional-cert-test.com"
...
3

Paste the copied example section into your existing sharded cluster resource.

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

4

Change the highlighted settings to your preferred values.

Key Type Necessity Description Example
spec.exposedExternally Boolean Optional Set this value to true to allow external services to connect to the MongoDB deployment. This results in Kubernetes creating a NodePort service. true
Key Type Necessity Description Example
spec.exposedExternally Boolean Optional Set this value to true to allow external services to connect to the MongoDB deployment. This results in Kubernetes creating a NodePort service. true
spec.security
boolean Optional

If this value is true, TLS is enabled on the MongoDB deployment.

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

true
spec.security.tls
collection Optional List of every domain that should be added to TLS certificates to each pod in this deployment. When you set this parameter, every CSR that the Kubernetes Operator transforms into a TLS certificate includes a SAN in the form <pod name>.<additional cert domain>. true
5

Save your sharded cluster config file.

6

Update and restart your sharded cluster deployment.

Invoke the following Kubernetes command to update and restart your sharded cluster:

kubectl apply -f <sharded-cluster-conf>.yaml
7

Discover the dynamically assigned NodePorts.

Discover the dynamically assigned NodePort:

kubectl get services -n <namespace>

The list output should contain an entry similar to the following:

NAME                      TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)           AGE

<my-sharded cluster>      NodePort    10.106.44.30    <none>        27017:30078/TCP   10s
  • Kubernetes exposes mongod on port 27017 within the Kubernetes container.
  • The NodePort service exposes the mongod via port 30078. NodePorts range from 30000 to 32767, inclusive.
8

Test the connection to the sharded cluster.

To connect to your deployment from outside of the Kubernetes cluster, run the mongod command with the external FQDN of a node as the --host flag.

Example

If a node in the Kubernetes cluster has an external FQDN of ec2-54-212-23-143.us-west-2.compute.amazonaws.com, you can connect to this sharded cluster instance from outside of the Kubernetes cluster using the following command:

mongo --host ec2-54-212-23-143.us-west-2.compute.amazonaws.com --port 30078

Tip

To obtain the external DNS of your Kubernetes cluster, you can run the following command:

kubectl describe nodes

This command displays the external DNS in the Addresses.ExternalDNS section of the output.

Alternatively, you can output the external DNS directly by running:

kubectl get nodes -o jsonpath='{ $.items[*].status.addresses[?(@.type=="ExternalDNS")].address }'