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Reconfigure MongoDB Shard

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

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 sharded database using a supported version by KubeDB operator. Then we are going to apply MongoDBOpsRequest to reconfigure its configuration.

Prepare MongoDB Shard

Now, we are going to deploy a MongoDB sharded database with version 3.6.8.

Deploy MongoDB database

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 configMap with this configuration file.

$ kubectl create configmap -n demo mg-custom-config --from-file=./mongod.conf
configmap/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-sharding
  namespace: demo
spec:
  version: 3.6.8-v1
  shardTopology:
    configServer:
      replicas: 2
      configSecret:
        name: mg-custom-config
      storage:
        resources:
          requests:
            storage: 1Gi
        storageClassName: standard
    mongos:
      replicas: 2
      configSecret:
        name: mg-custom-config
    shard:
      replicas: 2
      shards: 3
      configSecret:
        name: mg-custom-config
      storage:
        resources:
          requests:
            storage: 1Gi
        storageClassName: standard

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2020.11.12/docs/examples/mongodb/reconfigure/mg-shard-config.yaml
mongodb.kubedb.com/mg-sharding created

Now, wait until mg-sharding has status Running. i.e,

$ kubectl get mg -n demo                                                                                                                                             20:05:47
NAME          VERSION    STATUS    AGE
mg-sharding   3.6.8-v1   Running   3m23s

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-sharding-auth -o jsonpath='{.data.\username}' | base64 -d                                                                         11:09:51
root

$ kubectl get secrets -n demo mg-sharding-auth -o jsonpath='{.data.\password}' | base64 -d                                                                         11:10:44
Dv8F55zVNiEkhHM6

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

$ kubectl exec -n demo  mg-sharding-mongos-0  -- mongo admin -u root -p Dv8F55zVNiEkhHM6 --eval "db._adminCommand( {getCmdLineOpts: 1}).parsed.net" --quiet
  {
  	"bindIp" : "0.0.0.0",
  	"maxIncomingConnections" : 10000,
  	"port" : 27017,
  	"ssl" : {
  		"mode" : "disabled"
  	}
  }

$ kubectl exec -n demo  mg-sharding-configsvr-0  -- mongo admin -u root -p Dv8F55zVNiEkhHM6 --eval "db._adminCommand( {getCmdLineOpts: 1}).parsed.net" --quiet
  {
  	"bindIp" : "0.0.0.0",
  	"maxIncomingConnections" : 10000,
  	"port" : 27017,
  	"ssl" : {
  		"mode" : "disabled"
  	}
  }

$ kubectl exec -n demo  mg-sharding-shard0-0  -- mongo admin -u root -p Dv8F55zVNiEkhHM6 --eval "db._adminCommand( {getCmdLineOpts: 1}).parsed.net" --quiet
  {
  	"bindIp" : "0.0.0.0",
  	"maxIncomingConnections" : 10000,
  	"port" : 27017,
  	"ssl" : {
  		"mode" : "disabled"
  	}
  }

As we can see from the configuration of running mongodb, the value of maxIncomingConnections has been set to 10000 in all nodes.

Reconfigure using new ConfigMap

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 configMap with this configuration file.

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

Create MongoDBOpsRequest

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

apiVersion: ops.kubedb.com/v1alpha1
kind: MongoDBOpsRequest
metadata:
  name: mops-reconfigure-shard
  namespace: demo
spec:
  type: Reconfigure
  databaseRef:
    name: mg-sharding
  customConfig:
    shard:
      configMap:
        name: new-custom-config
    configServer:
      configMap:
        name: new-custom-config 
    mongos:
      configMap:
        name: new-custom-config   

Here,

  • spec.databaseRef.name specifies that we are reconfiguring mops-reconfigure-shard database.
  • spec.type specifies that we are performing Reconfigure on our database.
  • spec.customConfig.shard.configMap.name specifies the name of the new configmap for shard nodes.
  • spec.customConfig.configServer.configMap.name specifies the name of the new configmap for configServer nodes.
  • spec.customConfig.mongos.configMap.name specifies the name of the new configmap for mongos nodes.

Note: If you don’t want to reconfigure all the components together, you can only specify the components (shard, configServer and mongos) that you want to reconfigure.

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

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2020.11.12/docs/examples/mongodb/reconfigure/mops-reconfigure-shard.yaml
mongodbopsrequest.ops.kubedb.com/mops-reconfigure-shard created

Verify the new configuration is working

If everything goes well, KubeDB Enterprise operator will update the configSource 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-shard   Reconfigure   Successful   3m8s

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-shard  
Name:         mops-reconfigure-shard
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         MongoDBOpsRequest
Metadata:
  Creation Timestamp:  2020-09-29T17:16:47Z
  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:customConfig:
          .:
          f:configServer:
            .:
            f:configMap:
              .:
              f:name:
          f:mongos:
            .:
            f:configMap:
              .:
              f:name:
          f:shard:
            .:
            f:configMap:
              .:
              f:name:
        f:databaseRef:
          .:
          f:name:
        f:type:
    Manager:      kubectl-client-side-apply
    Operation:    Update
    Time:         2020-09-29T17:16:47Z
    API Version:  ops.kubedb.com/v1alpha1
    Fields Type:  FieldsV1
    fieldsV1:
      f:status:
        .:
        f:conditions:
        f:observedGeneration:
        f:phase:
    Manager:         kubedb-enterprise
    Operation:       Update
    Time:            2020-09-29T17:20:43Z
  Resource Version:  1857484
  Self Link:         /apis/ops.kubedb.com/v1alpha1/namespaces/demo/mongodbopsrequests/mops-reconfigure-shard
  UID:               fa02b9c6-83bd-4835-b72f-a027a0c8cf51
Spec:
  Custom Config:
    Config Server:
      Config Map:
        Name:  new-custom-config
    Mongos:
      Config Map:
        Name:  new-custom-config
    Shard:
      Config Map:
        Name:  new-custom-config
  Database Ref:
    Name:  mg-sharding
  Type:    Reconfigure
Status:
  Conditions:
    Last Transition Time:  2020-09-29T17:16:47Z
    Message:               MongoDB ops request is reconfiguring database
    Observed Generation:   1
    Reason:                Reconfigure
    Status:                True
    Type:                  Reconfigure
    Last Transition Time:  2020-09-29T17:16:47Z
    Message:               Successfully halted mongodb: mg-sharding
    Observed Generation:   1
    Reason:                HaltDatabase
    Status:                True
    Type:                  HaltDatabase
    Last Transition Time:  2020-09-29T17:17:32Z
    Message:               Successfully Reconfigured MongoDB
    Observed Generation:   1
    Reason:                ReconfigureMongos
    Status:                True
    Type:                  ReconfigureMongos
    Last Transition Time:  2020-09-29T17:18:22Z
    Message:               Successfully Reconfigured MongoDB
    Observed Generation:   1
    Reason:                ReconfigureConfigServer
    Status:                True
    Type:                  ReconfigureConfigServer
    Last Transition Time:  2020-09-29T17:20:42Z
    Message:               Successfully Reconfigured MongoDB
    Observed Generation:   1
    Reason:                ReconfigureShard
    Status:                True
    Type:                  ReconfigureShard
    Last Transition Time:  2020-09-29T17:20:42Z
    Message:               Successfully Resumed mongodb: mg-sharding
    Observed Generation:   1
    Reason:                ResumeDatabase
    Status:                True
    Type:                  ResumeDatabase
    Last Transition Time:  2020-09-29T17:20:43Z
    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  HaltDatabase            5m     KubeDB Enterprise Operator  Pausing MongoDB mg-sharding in Namespace demo
  Normal  HaltDatabase            5m     KubeDB Enterprise Operator  Successfully Halted MongoDB mg-sharding in Namespace demo
  Normal  ReconfigureMongos        4m15s  KubeDB Enterprise Operator  Successfully Reconfigured MongoDB
  Normal  ReconfigureConfigServer  3m25s  KubeDB Enterprise Operator  Successfully Reconfigured MongoDB
  Normal  ReconfigureShard         65s    KubeDB Enterprise Operator  Successfully Reconfigured MongoDB
  Normal  ResumeDatabase           65s    KubeDB Enterprise Operator  Resuming MongoDB
  Normal  ResumeDatabase           65s    KubeDB Enterprise Operator  Successfully Started Balancer
  Normal  Successful               65s    KubeDB Enterprise Operator  Successfully Reconfigured Database
  Normal  Successful               64s    KubeDB Enterprise Operator  Successfully Reconfigured Database

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

$ kubectl exec -n demo  mg-sharding-mongos-0  -- mongo admin -u root -p Dv8F55zVNiEkhHM6 --eval "db._adminCommand( {getCmdLineOpts: 1}).parsed.net" --quiet
  {
  	"bindIp" : "0.0.0.0",
  	"maxIncomingConnections" : 20000,
  	"port" : 27017,
  	"ssl" : {
  		"mode" : "disabled"
  	}
  }

$ kubectl exec -n demo  mg-sharding-configsvr-0  -- mongo admin -u root -p Dv8F55zVNiEkhHM6 --eval "db._adminCommand( {getCmdLineOpts: 1}).parsed.net" --quiet
  {
  	"bindIp" : "0.0.0.0",
  	"maxIncomingConnections" : 20000,
  	"port" : 27017,
  	"ssl" : {
  		"mode" : "disabled"
  	}
  }

$ kubectl exec -n demo  mg-sharding-shard0-0  -- mongo admin -u root -p Dv8F55zVNiEkhHM6 --eval "db._adminCommand( {getCmdLineOpts: 1}).parsed.net" --quiet
  {
  	"bindIp" : "0.0.0.0",
  	"maxIncomingConnections" : 20000,
  	"port" : 27017,
  	"ssl" : {
  		"mode" : "disabled"
  	}
  }

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

Reconfigure using new Data

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

Create MongoDBOpsRequest

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

apiVersion: ops.kubedb.com/v1alpha1
kind: MongoDBOpsRequest
metadata:
  name: mops-reconfigure-data-shard
  namespace: demo
spec:
  type: Reconfigure
  databaseRef:
    name: mg-sharding
  customConfig:
    shard:
      data:
        mongod.conf: |
          net:
            maxIncomingConnections: 30000
    configServer:
      data:
        mongod.conf: |
          net:
            maxIncomingConnections: 30000
    mongos:
      data:
        mongod.conf: |
          net:
            maxIncomingConnections: 30000

Here,

  • spec.databaseRef.name specifies that we are reconfiguring mops-reconfigure-data-shard database.
  • spec.type specifies that we are performing Reconfigure on our database.
  • spec.customConfig.shard.data specifies the new configuration that will be merged in the existing configMap for shard nodes.
  • spec.customConfig.configServer.data specifies the new configuration that will be merged in the existing configMap for configServer nodes.
  • spec.customConfig.mongos.data specifies the new configuration that will be merged in the existing configMap for mongos nodes.

Note: If you don’t want to reconfigure all the components together, you can only specify the components (shard, configServer and mongos) that you want to reconfigure.

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

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2020.11.12/docs/examples/mongodb/reconfigure/mops-reconfigure-data-shard.yaml
mongodbopsrequest.ops.kubedb.com/mops-reconfigure-data-shard 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-data-shard   Reconfigure   Successful   3m24s

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-data-shard
Name:         mops-reconfigure-data-shard
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         MongoDBOpsRequest
Metadata:
  Creation Timestamp:  2020-09-29T17:23:23Z
  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:customConfig:
          .:
          f:configServer:
            .:
            f:data:
              .:
              f:mongod.conf:
          f:mongos:
            .:
            f:data:
              .:
              f:mongod.conf:
          f:shard:
            .:
            f:data:
              .:
              f:mongod.conf:
        f:databaseRef:
          .:
          f:name:
        f:type:
    Manager:      kubectl-client-side-apply
    Operation:    Update
    Time:         2020-09-29T17:23:23Z
    API Version:  ops.kubedb.com/v1alpha1
    Fields Type:  FieldsV1
    fieldsV1:
      f:status:
        .:
        f:conditions:
        f:observedGeneration:
        f:phase:
    Manager:         kubedb-enterprise
    Operation:       Update
    Time:            2020-09-29T17:27:08Z
  Resource Version:  1858942
  Self Link:         /apis/ops.kubedb.com/v1alpha1/namespaces/demo/mongodbopsrequests/mops-reconfigure-data-shard
  UID:               05849063-3e57-4441-a6da-7a1c5393989a
Spec:
  Custom Config:
    Config Server:
      Data:
        mongod.conf:  net:
  maxIncomingConnections: 30000

    Mongos:
      Data:
        mongod.conf:  net:
  maxIncomingConnections: 30000

    Shard:
      Data:
        mongod.conf:  net:
  maxIncomingConnections: 30000

  Database Ref:
    Name:  mg-sharding
  Type:    Reconfigure
Status:
  Conditions:
    Last Transition Time:  2020-09-29T17:23:23Z
    Message:               MongoDB ops request is reconfiguring database
    Observed Generation:   1
    Reason:                Reconfigure
    Status:                True
    Type:                  Reconfigure
    Last Transition Time:  2020-09-29T17:24:08Z
    Message:               Successfully Reconfigured MongoDB
    Observed Generation:   1
    Reason:                ReconfigureMongos
    Status:                True
    Type:                  ReconfigureMongos
    Last Transition Time:  2020-09-29T17:24:58Z
    Message:               Successfully Reconfigured MongoDB
    Observed Generation:   1
    Reason:                ReconfigureConfigServer
    Status:                True
    Type:                  ReconfigureConfigServer
    Last Transition Time:  2020-09-29T17:27:08Z
    Message:               Successfully Reconfigured MongoDB
    Observed Generation:   1
    Reason:                ReconfigureShard
    Status:                True
    Type:                  ReconfigureShard
    Last Transition Time:  2020-09-29T17:27:08Z
    Message:               Successfully Resumed mongodb: mg-sharding
    Observed Generation:   1
    Reason:                ResumeDatabase
    Status:                True
    Type:                  ResumeDatabase
    Last Transition Time:  2020-09-29T17:27:08Z
    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  ReconfigureMongos        16m   KubeDB Enterprise Operator  Successfully Reconfigured MongoDB
  Normal  ReconfigureConfigServer  15m   KubeDB Enterprise Operator  Successfully Reconfigured MongoDB
  Normal  ReconfigureShard         13m   KubeDB Enterprise Operator  Successfully Reconfigured MongoDB
  Normal  ResumeDatabase           13m   KubeDB Enterprise Operator  Resuming MongoDB
  Normal  ResumeDatabase           13m   KubeDB Enterprise Operator  Successfully Started Balancer
  Normal  Successful               13m   KubeDB Enterprise Operator  Successfully Reconfigured Database
  Normal  Successful               13m   KubeDB Enterprise Operator  Successfully Reconfigured Database

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

$ kubectl exec -n demo  mg-sharding-mongos-0  -- mongo admin -u root -p Dv8F55zVNiEkhHM6 --eval "db._adminCommand( {getCmdLineOpts: 1}).parsed.net" --quiet
  {
  	"bindIp" : "0.0.0.0",
  	"maxIncomingConnections" : 30000,
  	"port" : 27017,
  	"ssl" : {
  		"mode" : "disabled"
  	}
  }

$ kubectl exec -n demo  mg-sharding-configsvr-0  -- mongo admin -u root -p Dv8F55zVNiEkhHM6 --eval "db._adminCommand( {getCmdLineOpts: 1}).parsed.net" --quiet
  {
  	"bindIp" : "0.0.0.0",
  	"maxIncomingConnections" : 30000,
  	"port" : 27017,
  	"ssl" : {
  		"mode" : "disabled"
  	}
  }

$ kubectl exec -n demo  mg-sharding-shard0-0  -- mongo admin -u root -p Dv8F55zVNiEkhHM6 --eval "db._adminCommand( {getCmdLineOpts: 1}).parsed.net" --quiet
  {
  	"bindIp" : "0.0.0.0",
  	"maxIncomingConnections" : 30000,
  	"port" : 27017,
  	"ssl" : {
  		"mode" : "disabled"
  	}
  }

As we can see from the configuration of running mongodb, the value of maxIncomingConnections has been changed from 20000 to 30000 in all nodes. So the reconfiguration of the database using the data field is successful.

Cleaning Up

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

kubectl delete mg -n demo mg-sharding
kubectl delete mongodbopsrequest -n demo mops-reconfigure-shard mops-reconfigure-data-shard