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Reconfigure MongoDB Replicaset Database

This guide will show you how to use KubeDB Enterprise operator to reconfigure a MongoDB Replicaset.

Before You Begin

  • At first, you need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster.

  • Install KubeDB Community and Enterprise operator in your cluster following the steps here.

  • You should be familiar with the following KubeDB concepts:

To keep everything isolated, we are going to use a separate namespace called demo throughout this tutorial.

$ kubectl create ns demo
namespace/demo created

Note: YAML files used in this tutorial are stored in docs/examples/mongodb directory of kubedb/docs repository.

Now, we are going to deploy a MongoDB Replicaset using a supported version by KubeDB operator. Then we are going to apply MongoDBOpsRequest to reconfigure its configuration.

Prepare MongoDB Replicaset

Now, we are going to deploy a MongoDB Replicaset database with version 4.2.3.

Deploy MongoDB

At first, we will create mongod.conf file containing required configuration settings.

$ cat mongod.conf
net:
   maxIncomingConnections: 10000

Here, maxIncomingConnections is set to 10000, whereas the default value is 65536.

Now, we will create a secret with this configuration file.

$ kubectl create secret generic -n demo mg-custom-config --from-file=./mongod.conf
secret/mg-custom-config created

In this section, we are going to create a MongoDB object specifying spec.configSecret field to apply this custom configuration. Below is the YAML of the MongoDB CR that we are going to create,

apiVersion: kubedb.com/v1alpha2
kind: MongoDB
metadata:
  name: mg-replicaset
  namespace: demo
spec:
  version: "4.2.3"
  replicas: 3
  replicaSet:
    name: rs0
  storageType: Durable
  storage:
    storageClassName: "standard"
    accessModes:
    - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
  configSecret:
    name: mg-custom-config

Let’s create the MongoDB CR we have shown above,

$ kubectl create -f https://github.com/kubedb/docs/raw/v2021.04.16/docs/examples/mongodb/reconfigure/mg-replicaset-config.yaml
mongodb.kubedb.com/mg-replicaset created

Now, wait until mg-replicaset has status Ready. i.e,

$ kubectl get mg -n demo                                                                                                                                            
NAME            VERSION   STATUS   AGE
mg-replicaset   4.2.3     Ready    19m

Now, we will check if the database has started with the custom configuration we have provided.

First we need to get the username and password to connect to a mongodb instance,

$ kubectl get secrets -n demo mg-replicaset-auth -o jsonpath='{.data.\username}' | base64 -d                                                                       
root

$ kubectl get secrets -n demo mg-replicaset-auth -o jsonpath='{.data.\password}' | base64 -d                                                                         
nrKuxni0wDSMrgwy

Now let’s connect to a mongodb instance and run a mongodb internal command to check the configuration we have provided.

$ kubectl exec -n demo  mg-replicaset-0  -- mongo admin -u root -p nrKuxni0wDSMrgwy --eval "db._adminCommand( {getCmdLineOpts: 1})" --quiet                        
{
	"argv" : [
		"mongod",
		"--dbpath=/data/db",
		"--auth",
		"--ipv6",
		"--bind_ip_all",
		"--port=27017",
		"--tlsMode=disabled",
		"--replSet=rs0",
		"--keyFile=/data/configdb/key.txt",
		"--clusterAuthMode=keyFile",
		"--config=/data/configdb/mongod.conf"
	],
	"parsed" : {
		"config" : "/data/configdb/mongod.conf",
		"net" : {
			"bindIp" : "*",
			"ipv6" : true,
			"maxIncomingConnections" : 10000,
			"port" : 27017,
			"tls" : {
				"mode" : "disabled"
			}
		},
		"replication" : {
			"replSet" : "rs0"
		},
		"security" : {
			"authorization" : "enabled",
			"clusterAuthMode" : "keyFile",
			"keyFile" : "/data/configdb/key.txt"
		},
		"storage" : {
			"dbPath" : "/data/db"
		}
	},
	"ok" : 1,
	"$clusterTime" : {
		"clusterTime" : Timestamp(1614668500, 1),
		"signature" : {
			"hash" : BinData(0,"7sh886HhsNYajGxYGp5Jxi52IzA="),
			"keyId" : NumberLong("6934943333319966722")
		}
	},
	"operationTime" : Timestamp(1614668500, 1)
}

As we can see from the configuration of ready mongodb, the value of maxIncomingConnections has been set to 10000.

Reconfigure using new config secret

Now we will reconfigure this database to set maxIncomingConnections to 20000.

Now, we will edit the mongod.conf file containing required configuration settings.

$ cat mongod.conf
net:
   maxIncomingConnections: 20000

Then, we will create a new secret with this configuration file.

$ kubectl create secret generic -n demo new-custom-config --from-file=./mongod.conf
secret/new-custom-config created

Create MongoDBOpsRequest

Now, we will use this secret to replace the previous secret using a MongoDBOpsRequest CR. The MongoDBOpsRequest yaml is given below,

apiVersion: ops.kubedb.com/v1alpha1
kind: MongoDBOpsRequest
metadata:
  name: mops-reconfigure-replicaset
  namespace: demo
spec:
  type: Reconfigure
  databaseRef:
    name: mg-replicaset
  configuration:
    replicaSet:
      configSecret:
        name: new-custom-config

Here,

  • spec.databaseRef.name specifies that we are reconfiguring mops-reconfigure-replicaset database.
  • spec.type specifies that we are performing Reconfigure on our database.
  • spec.customConfig.replicaSet.configSecret.name specifies the name of the new secret.

Let’s create the MongoDBOpsRequest CR we have shown above,

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2021.04.16/docs/examples/mongodb/reconfigure/mops-reconfigure-replicaset.yaml
mongodbopsrequest.ops.kubedb.com/mops-reconfigure-replicaset created

Verify the new configuration is working

If everything goes well, KubeDB Enterprise operator will update the configSecret of MongoDB object.

Let’s wait for MongoDBOpsRequest to be Successful. Run the following command to watch MongoDBOpsRequest CR,

$ watch kubectl get mongodbopsrequest -n demo
Every 2.0s: kubectl get mongodbopsrequest -n demo
NAME                          TYPE          STATUS       AGE
mops-reconfigure-replicaset   Reconfigure   Successful   113s

We can see from the above output that the MongoDBOpsRequest has succeeded. If we describe the MongoDBOpsRequest we will get an overview of the steps that were followed to reconfigure the database.

$ kubectl describe mongodbopsrequest -n demo mops-reconfigure-replicaset 
Name:         mops-reconfigure-replicaset
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         MongoDBOpsRequest
Metadata:
  Creation Timestamp:  2021-03-02T07:04:31Z
  Generation:          1
  Managed Fields:
    API Version:  ops.kubedb.com/v1alpha1
    Fields Type:  FieldsV1
    fieldsV1:
      f:metadata:
        f:annotations:
          .:
          f:kubectl.kubernetes.io/last-applied-configuration:
      f:spec:
        .:
        f:configuration:
          .:
          f:replicaSet:
            .:
            f:configSecret:
              .:
              f:name:
        f:databaseRef:
          .:
          f:name:
        f:type:
    Manager:      kubectl-client-side-apply
    Operation:    Update
    Time:         2021-03-02T07:04:31Z
    API Version:  ops.kubedb.com/v1alpha1
    Fields Type:  FieldsV1
    fieldsV1:
      f:spec:
        f:configuration:
          f:replicaSet:
            f:podTemplate:
              .:
              f:controller:
              f:metadata:
              f:spec:
                .:
                f:resources:
      f:status:
        .:
        f:conditions:
        f:observedGeneration:
        f:phase:
    Manager:         kubedb-enterprise
    Operation:       Update
    Time:            2021-03-02T07:04:31Z
  Resource Version:  29869
  Self Link:         /apis/ops.kubedb.com/v1alpha1/namespaces/demo/mongodbopsrequests/mops-reconfigure-replicaset
  UID:               064733d6-19db-4153-82f7-bc0580116ee6
Spec:
  Configuration:
    Replica Set:
      Config Secret:
        Name:  new-custom-config
  Database Ref:
    Name:  mg-replicaset
  Type:    Reconfigure
Status:
  Conditions:
    Last Transition Time:  2021-03-02T07:04:31Z
    Message:               MongoDB ops request is reconfiguring database
    Observed Generation:   1
    Reason:                Reconfigure
    Status:                True
    Type:                  Reconfigure
    Last Transition Time:  2021-03-02T07:06:21Z
    Message:               Successfully Reconfigured MongoDB
    Observed Generation:   1
    Reason:                ReconfigureReplicaset
    Status:                True
    Type:                  ReconfigureReplicaset
    Last Transition Time:  2021-03-02T07:06:21Z
    Message:               Successfully completed the modification process.
    Observed Generation:   1
    Reason:                Successful
    Status:                True
    Type:                  Successful
  Observed Generation:     1
  Phase:                   Successful
Events:
  Type    Reason                 Age    From                        Message
  ----    ------                 ----   ----                        -------
  Normal  PauseDatabase          2m55s  KubeDB Enterprise Operator  Pausing MongoDB demo/mg-replicaset
  Normal  PauseDatabase          2m55s  KubeDB Enterprise Operator  Successfully paused MongoDB demo/mg-replicaset
  Normal  ReconfigureReplicaset  65s    KubeDB Enterprise Operator  Successfully Reconfigured MongoDB
  Normal  ResumeDatabase         65s    KubeDB Enterprise Operator  Resuming MongoDB demo/mg-replicaset
  Normal  ResumeDatabase         65s    KubeDB Enterprise Operator  Successfully resumed MongoDB demo/mg-replicaset
  Normal  Successful             65s    KubeDB Enterprise Operator  Successfully Reconfigured Database

Now let’s connect to a mongodb instance and run a mongodb internal command to check the new configuration we have provided.

$ kubectl exec -n demo  mg-replicaset-0  -- mongo admin -u root -p nrKuxni0wDSMrgwy --eval "db._adminCommand( {getCmdLineOpts: 1})" --quiet
{
	"argv" : [
		"mongod",
		"--dbpath=/data/db",
		"--auth",
		"--ipv6",
		"--bind_ip_all",
		"--port=27017",
		"--tlsMode=disabled",
		"--replSet=rs0",
		"--keyFile=/data/configdb/key.txt",
		"--clusterAuthMode=keyFile",
		"--config=/data/configdb/mongod.conf"
	],
	"parsed" : {
		"config" : "/data/configdb/mongod.conf",
		"net" : {
			"bindIp" : "*",
			"ipv6" : true,
			"maxIncomingConnections" : 20000,
			"port" : 27017,
			"tls" : {
				"mode" : "disabled"
			}
		},
		"replication" : {
			"replSet" : "rs0"
		},
		"security" : {
			"authorization" : "enabled",
			"clusterAuthMode" : "keyFile",
			"keyFile" : "/data/configdb/key.txt"
		},
		"storage" : {
			"dbPath" : "/data/db"
		}
	},
	"ok" : 1,
	"$clusterTime" : {
		"clusterTime" : Timestamp(1614668887, 1),
		"signature" : {
			"hash" : BinData(0,"5q35Y51+YpbVHFKoaU7lUWi38oY="),
			"keyId" : NumberLong("6934943333319966722")
		}
	},
	"operationTime" : Timestamp(1614668887, 1)
}

As we can see from the configuration of ready mongodb, the value of maxIncomingConnections has been changed from 10000 to 20000. So the reconfiguration of the database is successful.

Reconfigure using inline config

Now we will reconfigure this database again to set maxIncomingConnections to 30000. This time we won’t use a new secret. We will use the inlineConfig field of the MongoDBOpsRequest. This will merge the new config in the existing secret.

Create MongoDBOpsRequest

Now, we will use the new configuration in the inlineConfig field in the MongoDBOpsRequest CR. The MongoDBOpsRequest yaml is given below,

apiVersion: ops.kubedb.com/v1alpha1
kind: MongoDBOpsRequest
metadata:
  name: mops-reconfigure-inline-replicaset
  namespace: demo
spec:
  type: Reconfigure
  databaseRef:
    name: mg-replicaset
  configuration:
    replicaSet:
      inlineConfig: |
          net:
            maxIncomingConnections: 30000          

Here,

  • spec.databaseRef.name specifies that we are reconfiguring mops-reconfigure-inline-replicaset database.
  • spec.type specifies that we are performing Reconfigure on our database.
  • spec.configuration.replicaSet.inlineConfig specifies the new configuration that will be merged in the existing secret.

Let’s create the MongoDBOpsRequest CR we have shown above,

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2021.04.16/docs/examples/mongodb/reconfigure/mops-reconfigure-inline-replicaset.yaml
mongodbopsrequest.ops.kubedb.com/mops-reconfigure-inline-replicaset created

Verify the new configuration is working

If everything goes well, KubeDB Enterprise operator will merge this new config with the existing configuration.

Let’s wait for MongoDBOpsRequest to be Successful. Run the following command to watch MongoDBOpsRequest CR,

$ watch kubectl get mongodbopsrequest -n demo
Every 2.0s: kubectl get mongodbopsrequest -n demo
NAME                               TYPE          STATUS       AGE
mops-reconfigure-inline-replicaset   Reconfigure   Successful   109s

We can see from the above output that the MongoDBOpsRequest has succeeded. If we describe the MongoDBOpsRequest we will get an overview of the steps that were followed to reconfigure the database.

$ kubectl describe mongodbopsrequest -n demo mops-reconfigure-inline-replicaset
Name:         mops-reconfigure-inline-replicaset
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         MongoDBOpsRequest
Metadata:
  Creation Timestamp:  2021-03-02T07:09:39Z
  Generation:          1
  Managed Fields:
    API Version:  ops.kubedb.com/v1alpha1
    Fields Type:  FieldsV1
    fieldsV1:
      f:metadata:
        f:annotations:
          .:
          f:kubectl.kubernetes.io/last-applied-configuration:
      f:spec:
        .:
        f:configuration:
          .:
          f:replicaSet:
            .:
            f:inlineConfig:
        f:databaseRef:
          .:
          f:name:
        f:type:
    Manager:      kubectl-client-side-apply
    Operation:    Update
    Time:         2021-03-02T07:09:39Z
    API Version:  ops.kubedb.com/v1alpha1
    Fields Type:  FieldsV1
    fieldsV1:
      f:spec:
        f:configuration:
          f:replicaSet:
            f:podTemplate:
              .:
              f:controller:
              f:metadata:
              f:spec:
                .:
                f:resources:
      f:status:
        .:
        f:conditions:
        f:observedGeneration:
        f:phase:
    Manager:         kubedb-enterprise
    Operation:       Update
    Time:            2021-03-02T07:09:39Z
  Resource Version:  31005
  Self Link:         /apis/ops.kubedb.com/v1alpha1/namespaces/demo/mongodbopsrequests/mops-reconfigure-inline-replicaset
  UID:               0137442b-1b04-43ed-8de7-ecd913b44065
Spec:
  Configuration:
    Replica Set:
      Inline Config:  net:
  maxIncomingConnections: 30000

  Database Ref:
    Name:  mg-replicaset
  Type:    Reconfigure
Status:
  Conditions:
    Last Transition Time:  2021-03-02T07:09:39Z
    Message:               MongoDB ops request is reconfiguring database
    Observed Generation:   1
    Reason:                Reconfigure
    Status:                True
    Type:                  Reconfigure
    Last Transition Time:  2021-03-02T07:11:14Z
    Message:               Successfully Reconfigured MongoDB
    Observed Generation:   1
    Reason:                ReconfigureReplicaset
    Status:                True
    Type:                  ReconfigureReplicaset
    Last Transition Time:  2021-03-02T07:11:14Z
    Message:               Successfully completed the modification process.
    Observed Generation:   1
    Reason:                Successful
    Status:                True
    Type:                  Successful
  Observed Generation:     1
  Phase:                   Successful
Events:
  Type    Reason                 Age    From                        Message
  ----    ------                 ----   ----                        -------
  Normal  PauseDatabase          9m20s  KubeDB Enterprise Operator  Pausing MongoDB demo/mg-replicaset
  Normal  PauseDatabase          9m20s  KubeDB Enterprise Operator  Successfully paused MongoDB demo/mg-replicaset
  Normal  ReconfigureReplicaset  7m45s  KubeDB Enterprise Operator  Successfully Reconfigured MongoDB
  Normal  ResumeDatabase         7m45s  KubeDB Enterprise Operator  Resuming MongoDB demo/mg-replicaset
  Normal  ResumeDatabase         7m45s  KubeDB Enterprise Operator  Successfully resumed MongoDB demo/mg-replicaset
  Normal  Successful             7m45s  KubeDB Enterprise Operator  Successfully Reconfigured Database

Now let’s connect to a mongodb instance and run a mongodb internal command to check the new configuration we have provided.

$ kubectl exec -n demo  mg-replicaset-0  -- mongo admin -u root -p nrKuxni0wDSMrgwy --eval "db._adminCommand( {getCmdLineOpts: 1})" --quiet
{
	"argv" : [
		"mongod",
		"--dbpath=/data/db",
		"--auth",
		"--ipv6",
		"--bind_ip_all",
		"--port=27017",
		"--tlsMode=disabled",
		"--replSet=rs0",
		"--keyFile=/data/configdb/key.txt",
		"--clusterAuthMode=keyFile",
		"--config=/data/configdb/mongod.conf"
	],
	"parsed" : {
		"config" : "/data/configdb/mongod.conf",
		"net" : {
			"bindIp" : "*",
			"ipv6" : true,
			"maxIncomingConnections" : 30000,
			"port" : 27017,
			"tls" : {
				"mode" : "disabled"
			}
		},
		"replication" : {
			"replSet" : "rs0"
		},
		"security" : {
			"authorization" : "enabled",
			"clusterAuthMode" : "keyFile",
			"keyFile" : "/data/configdb/key.txt"
		},
		"storage" : {
			"dbPath" : "/data/db"
		}
	},
	"ok" : 1,
	"$clusterTime" : {
		"clusterTime" : Timestamp(1614669580, 1),
		"signature" : {
			"hash" : BinData(0,"u/xTAa4aW/8bsRvBYPffwQCeTF0="),
			"keyId" : NumberLong("6934943333319966722")
		}
	},
	"operationTime" : Timestamp(1614669580, 1)
}

As we can see from the configuration of ready mongodb, the value of maxIncomingConnections has been changed from 20000 to 30000. So the reconfiguration of the database using the inlineConfig field is successful.

Cleaning Up

To clean up the Kubernetes resources created by this tutorial, run:

kubectl delete mg -n demo mg-replicaset
kubectl delete mongodbopsrequest -n demo mops-reconfigure-replicaset mops-reconfigure-inline-replicaset