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Changing MongoDB Options

You may require a configuration change for your application. MongoDB allows configuring the database with a configuration file, as many other database management systems do. You can pass options to MongoDB instances in the cluster in one of the following ways:

  • edit the deploy/cr.yaml file,
  • use a ConfigMap,
  • use a Secret object.

You can pass configuration settings separately for mongod Pods, mongos Pods, and Config Server Pods.

Edit the deploy/cr.yaml file

You can add MongoDB configuration options to the replsets.configuration, sharding.mongos.configuration, and sharding-configsvrreplset-configuration keys of the deploy/cr.yaml. Here is an example:

spec:
  ...
  replsets:
    - name: rs0
      size: 3
      configuration: |
        operationProfiling:
          mode: slowOp
        systemLog:
          verbosity: 1
      ...

See the official manual for the complete list of options, as well as specific Percona Server for MongoDB documentation pages.

Use a ConfigMap

You can use a ConfigMap and the cluster restart to reset configuration options. A ConfigMap allows Kubernetes to pass or update configuration data inside a containerized application.

You should give the ConfigMap a specific name, which is composed of your cluster name and a specific suffix:

  • my-cluster-name-rs0-mongod for the Replica Set (mongod) Pods,
  • my-cluster-name-cfg-mongod for the Config Server Pods,
  • my-cluster-name-mongos for the mongos Pods,

Note

To find the cluster name, you can use the following command:

$ kubectl get psmdb

For example, let’s define a mongod.conf configuration file and put there several MongoDB options we used in the previous example:

operationProfiling:
  mode: slowOp
systemLog:
  verbosity: 1

You can create a ConfigMap from the mongod.conf file with the kubectl create configmap command. It has the following syntax:

$ kubectl create configmap <configmap-name> <resource-type=resource-name>

The following example defines my-cluster-name-rs0-mongod as the ConfigMap name and the mongod.conf file as the data source:

$ kubectl create configmap my-cluster-name-rs0-mongod --from-file=mongod.conf=mongod.conf

To view the created ConfigMap, use the following command:

$ kubectl describe configmaps my-cluster-name-rs0-mongod

Note

Do not forget to restart Percona Server for MongoDB to ensure the cluster has updated the configuration (see details on how to connect in the Install Percona Server for MongoDB on Kubernetes page).

Use a Secret Object

The Operator can also store configuration options in Kubernetes Secrets. This can be useful if you need additional protection for some sensitive data.

You should create a Secret object with a specific name, composed of your cluster name and a specific suffix:

  • my-cluster-name-rs0-mongod for the Replica Set Pods,
  • my-cluster-name-cfg-mongod for the Config Server Pods,
  • my-cluster-name-mongos for the mongos Pods,

Note

To find the cluster name, you can use the following command:

$ kubectl get psmdb

Configuration options should be put inside a specific key:

  • data.mongod key for Replica Set (mongod) and Config Server Pods,
  • data.mongos key for mongos Pods.

Actual options should be encoded with Base64.

For example, let’s define a mongod.conf configuration file and put there several MongoDB options we used in the previous example:

operationProfiling:
  mode: slowOp
systemLog:
  verbosity: 1

You can get a Base64 encoded string from your options via the command line as follows:

$ cat mongod.conf | base64 --wrap=0
$ cat mongod.conf | base64

Note

Similarly, you can read the list of options from a Base64 encoded string:

$ echo "ICAgICAgb3BlcmF0aW9uUHJvZmlsaW5nOgogICAgICAgIG1vZGU6IHNsb3dPc\
AogICAgICBzeXN0ZW1Mb2c6CiAgICAgICAgdmVyYm9zaXR5OiAxCg==" | base64 --decode

Finally, use a yaml file to create the Secret object. For example, you can create a deploy/my-mongod-secret.yaml file with the following contents:

apiVersion: v1
kind: Secret
metadata:
  name: my-cluster-name-rs0-mongod
data:
  mongod.conf: "ICAgICAgb3BlcmF0aW9uUHJvZmlsaW5nOgogICAgICAgIG1vZGU6IHNsb3dPc\
   AogICAgICBzeXN0ZW1Mb2c6CiAgICAgICAgdmVyYm9zaXR5OiAxCg=="

When ready, apply it with the following command:

$ kubectl create -f deploy/my-mongod-secret.yaml

Note

Do not forget to restart Percona Server for MongoDB to ensure the cluster has updated the configuration (see details on how to connect in the Install Percona Server for MongoDB on Kubernetes page).


Last update: 2022-11-03