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Horizontal Scale MongoDB Shard
This guide will show you how to use KubeDB Ops-manager operator to scale the shard of a MongoDB database.
Before You Begin
At first, you need to have a Kubernetes cluster, and the
kubectlcommand-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using kind.Install
KubeDBProvisioner and Ops-manager operator in your cluster following the steps here.You should be familiar with the following
KubeDBconcepts:
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.
Apply Horizontal Scaling on Sharded Database
Here, we are going to deploy a MongoDB sharded database using a supported version by KubeDB operator. Then we are going to apply horizontal scaling on it.
Prepare MongoDB Sharded Database
Now, we are going to deploy a MongoDB sharded database with version 4.2.3.
Deploy MongoDB Sharded Database
In this section, we are going to deploy a MongoDB sharded database. Then, in the next sections we will scale shards of the database using MongoDBOpsRequest CRD. 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: 4.2.3
shardTopology:
configServer:
replicas: 3
storage:
resources:
requests:
storage: 1Gi
storageClassName: standard
mongos:
replicas: 2
shard:
replicas: 3
shards: 2
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/v2023.06.19/docs/examples/mongodb/scaling/mg-shard.yaml
mongodb.kubedb.com/mg-sharding created
Now, wait until mg-sharding has status Ready. i.e,
$ kubectl get mg -n demo
NAME VERSION STATUS AGE
mg-sharding 4.2.3 Ready 10m
Verify Number of Shard and Shard Replicas
Let’s check the number of shards this database from the MongoDB object and the number of statefulsets it has,
$ kubectl get mongodb -n demo mg-sharding -o json | jq '.spec.shardTopology.shard.shards'
2
$ kubectl get sts -n demo
NAME READY AGE
mg-sharding-configsvr 3/3 23m
mg-sharding-mongos 2/2 22m
mg-sharding-shard0 3/3 23m
mg-sharding-shard1 3/3 23m
So, We can see from the both output that the database has 2 shards.
Now, Let’s check the number of replicas each shard has from the MongoDB object and the number of pod the statefulsets have,
$ kubectl get mongodb -n demo mg-sharding -o json | jq '.spec.shardTopology.shard.replicas'
3
$ kubectl get sts -n demo mg-sharding-shard0 -o json | jq '.spec.replicas'
3
We can see from both output that the database has 3 replicas in each shards.
Also, we can verify the number of shard from an internal mongodb command by execing into a mongos node.
First we need to get the username and password to connect to a mongos instance,
$ kubectl get secrets -n demo mg-sharding-auth -o jsonpath='{.data.\username}' | base64 -d
root
$ kubectl get secrets -n demo mg-sharding-auth -o jsonpath='{.data.\password}' | base64 -d
xBC-EwMFivFCgUlK
Now let’s connect to a mongos instance and run a mongodb internal command to check the number of shards,
$ kubectl exec -n demo mg-sharding-mongos-0 -- mongo admin -u root -p xBC-EwMFivFCgUlK --eval "sh.status()" --quiet
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId("603e5a4bec470e6b4197e10b")
}
shards:
{ "_id" : "shard0", "host" : "shard0/mg-sharding-shard0-0.mg-sharding-shard0-pods.demo.svc.cluster.local:27017,mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017,mg-sharding-shard0-2.mg-sharding-shard0-pods.demo.svc.cluster.local:27017", "state" : 1 }
{ "_id" : "shard1", "host" : "shard1/mg-sharding-shard1-0.mg-sharding-shard1-pods.demo.svc.cluster.local:27017,mg-sharding-shard1-1.mg-sharding-shard1-pods.demo.svc.cluster.local:27017,mg-sharding-shard1-2.mg-sharding-shard1-pods.demo.svc.cluster.local:27017", "state" : 1 }
active mongoses:
"4.2.3" : 2
autosplit:
Currently enabled: yes
balancer:
Currently enabled: yes
Currently running: no
Failed balancer rounds in last 5 attempts: 0
Migration Results for the last 24 hours:
No recent migrations
databases:
{ "_id" : "config", "primary" : "config", "partitioned" : true }
We can see from the above output that the number of shard is 2.
Also, we can verify the number of replicas each shard has from an internal mongodb command by execing into a shard node.
Now let’s connect to a shard instance and run a mongodb internal command to check the number of replicas,
$ kubectl exec -n demo mg-sharding-shard0-0 -- mongo admin -u root -p xBC-EwMFivFCgUlK --eval "db.adminCommand( { replSetGetStatus : 1 } ).members" --quiet
[
{
"_id" : 0,
"name" : "mg-sharding-shard0-0.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 338,
"optime" : {
"ts" : Timestamp(1614699416, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2021-03-02T15:36:56Z"),
"syncingTo" : "",
"syncSourceHost" : "",
"syncSourceId" : -1,
"infoMessage" : "",
"electionTime" : Timestamp(1614699092, 1),
"electionDate" : ISODate("2021-03-02T15:31:32Z"),
"configVersion" : 3,
"self" : true,
"lastHeartbeatMessage" : ""
},
{
"_id" : 1,
"name" : "mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 291,
"optime" : {
"ts" : Timestamp(1614699413, 1),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1614699413, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2021-03-02T15:36:53Z"),
"optimeDurableDate" : ISODate("2021-03-02T15:36:53Z"),
"lastHeartbeat" : ISODate("2021-03-02T15:36:56.692Z"),
"lastHeartbeatRecv" : ISODate("2021-03-02T15:36:56.015Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncingTo" : "mg-sharding-shard0-0.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"syncSourceHost" : "mg-sharding-shard0-0.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 0,
"infoMessage" : "",
"configVersion" : 3
},
{
"_id" : 2,
"name" : "mg-sharding-shard0-2.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 259,
"optime" : {
"ts" : Timestamp(1614699413, 1),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1614699413, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2021-03-02T15:36:53Z"),
"optimeDurableDate" : ISODate("2021-03-02T15:36:53Z"),
"lastHeartbeat" : ISODate("2021-03-02T15:36:56.732Z"),
"lastHeartbeatRecv" : ISODate("2021-03-02T15:36:57.773Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncingTo" : "mg-sharding-shard0-0.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"syncSourceHost" : "mg-sharding-shard0-0.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 0,
"infoMessage" : "",
"configVersion" : 3
}
]
We can see from the above output that the number of replica is 3.
Verify Number of ConfigServer
Let’s check the number of replicas this database has from the MongoDB object, number of pods the statefulset have,
$ kubectl get mongodb -n demo mg-sharding -o json | jq '.spec.shardTopology.configServer.replicas'
3
$ kubectl get sts -n demo mg-sharding-configsvr -o json | jq '.spec.replicas'
3
We can see from both command that the database has 3 replicas in the configServer.
Now let’s connect to a mongodb instance and run a mongodb internal command to check the number of replicas,
$ kubectl exec -n demo mg-sharding-configsvr-0 -- mongo admin -u root -p xBC-EwMFivFCgUlK --eval "db.adminCommand( { replSetGetStatus : 1 } ).members" --quiet
[
{
"_id" : 0,
"name" : "mg-sharding-configsvr-0.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 423,
"optime" : {
"ts" : Timestamp(1614699492, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2021-03-02T15:38:12Z"),
"syncingTo" : "",
"syncSourceHost" : "",
"syncSourceId" : -1,
"infoMessage" : "",
"electionTime" : Timestamp(1614699081, 2),
"electionDate" : ISODate("2021-03-02T15:31:21Z"),
"configVersion" : 3,
"self" : true,
"lastHeartbeatMessage" : ""
},
{
"_id" : 1,
"name" : "mg-sharding-configsvr-1.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 385,
"optime" : {
"ts" : Timestamp(1614699492, 1),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1614699492, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2021-03-02T15:38:12Z"),
"optimeDurableDate" : ISODate("2021-03-02T15:38:12Z"),
"lastHeartbeat" : ISODate("2021-03-02T15:38:13.573Z"),
"lastHeartbeatRecv" : ISODate("2021-03-02T15:38:12.725Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncingTo" : "mg-sharding-configsvr-0.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"syncSourceHost" : "mg-sharding-configsvr-0.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 0,
"infoMessage" : "",
"configVersion" : 3
},
{
"_id" : 2,
"name" : "mg-sharding-configsvr-2.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 340,
"optime" : {
"ts" : Timestamp(1614699490, 8),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1614699490, 8),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2021-03-02T15:38:10Z"),
"optimeDurableDate" : ISODate("2021-03-02T15:38:10Z"),
"lastHeartbeat" : ISODate("2021-03-02T15:38:11.665Z"),
"lastHeartbeatRecv" : ISODate("2021-03-02T15:38:11.827Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncingTo" : "mg-sharding-configsvr-0.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"syncSourceHost" : "mg-sharding-configsvr-0.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 0,
"infoMessage" : "",
"configVersion" : 3
}
]
We can see from the above output that the configServer has 3 nodes.
Verify Number of Mongos
Let’s check the number of replicas this database has from the MongoDB object, number of pods the statefulset have,
$ kubectl get mongodb -n demo mg-sharding -o json | jq '.spec.shardTopology.mongos.replicas'
2
$ kubectl get sts -n demo mg-sharding-mongos -o json | jq '.spec.replicas'
2
We can see from both command that the database has 2 replicas in the mongos.
Now let’s connect to a mongodb instance and run a mongodb internal command to check the number of replicas,
$ kubectl exec -n demo mg-sharding-mongos-0 -- mongo admin -u root -p xBC-EwMFivFCgUlK --eval "sh.status()" --quiet
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId("603e5a4bec470e6b4197e10b")
}
shards:
{ "_id" : "shard0", "host" : "shard0/mg-sharding-shard0-0.mg-sharding-shard0-pods.demo.svc.cluster.local:27017,mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017,mg-sharding-shard0-2.mg-sharding-shard0-pods.demo.svc.cluster.local:27017", "state" : 1 }
{ "_id" : "shard1", "host" : "shard1/mg-sharding-shard1-0.mg-sharding-shard1-pods.demo.svc.cluster.local:27017,mg-sharding-shard1-1.mg-sharding-shard1-pods.demo.svc.cluster.local:27017,mg-sharding-shard1-2.mg-sharding-shard1-pods.demo.svc.cluster.local:27017", "state" : 1 }
active mongoses:
"4.2.3" : 2
autosplit:
Currently enabled: yes
balancer:
Currently enabled: yes
Currently running: no
Failed balancer rounds in last 5 attempts: 0
Migration Results for the last 24 hours:
No recent migrations
databases:
{ "_id" : "config", "primary" : "config", "partitioned" : true }
We can see from the above output that the mongos has 2 active nodes.
We are now ready to apply the MongoDBOpsRequest CR to update scale up and down all the components of the database.
Scale Up
Here, we are going to scale up all the components of the database to meet the desired number of replicas after scaling.
Create MongoDBOpsRequest
In order to scale up, we have to create a MongoDBOpsRequest CR with our configuration. Below is the YAML of the MongoDBOpsRequest CR that we are going to create,
apiVersion: ops.kubedb.com/v1alpha1
kind: MongoDBOpsRequest
metadata:
name: mops-hscale-up-shard
namespace: demo
spec:
type: HorizontalScaling
databaseRef:
name: mg-sharding
horizontalScaling:
shard:
shards: 3
replicas: 4
mongos:
replicas: 3
configServer:
replicas: 4
Here,
spec.databaseRef.namespecifies that we are performing horizontal scaling operation onmops-hscale-up-sharddatabase.spec.typespecifies that we are performingHorizontalScalingon our database.spec.horizontalScaling.shard.shardsspecifies the desired number of shards after scaling.spec.horizontalScaling.shard.replicasspecifies the desired number of replicas of each shard after scaling.spec.horizontalScaling.mongos.replicasspecifies the desired replicas after scaling.spec.horizontalScaling.configServer.replicasspecifies the desired replicas after scaling.
Note: If you don’t want to scale all the components together, you can only specify the components (shard, configServer and mongos) that you want to scale.
Let’s create the MongoDBOpsRequest CR we have shown above,
$ kubectl apply -f https://github.com/kubedb/docs/raw/v2023.06.19/docs/examples/mongodb/scaling/horizontal-scaling/mops-hscale-up-shard.yaml
mongodbopsrequest.ops.kubedb.com/mops-hscale-up-shard created
Verify scaling up is successful
If everything goes well, KubeDB Ops-manager operator will update the shard and replicas of MongoDB object and related StatefulSets and Pods.
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-hscale-up-shard HorizontalScaling Successful 9m57s
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 scale the database.
$ kubectl describe mongodbopsrequest -n demo mops-hscale-up-shard
Name: mops-hscale-up-shard
Namespace: demo
Labels: <none>
Annotations: <none>
API Version: ops.kubedb.com/v1alpha1
Kind: MongoDBOpsRequest
Metadata:
Creation Timestamp: 2021-03-02T16:23:16Z
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:databaseRef:
.:
f:name:
f:horizontalScaling:
.:
f:configServer:
.:
f:replicas:
f:mongos:
.:
f:replicas:
f:shard:
.:
f:replicas:
f:shards:
f:type:
Manager: kubectl-client-side-apply
Operation: Update
Time: 2021-03-02T16:23:16Z
API Version: ops.kubedb.com/v1alpha1
Fields Type: FieldsV1
fieldsV1:
f:status:
.:
f:conditions:
f:observedGeneration:
f:phase:
Manager: kubedb-enterprise
Operation: Update
Time: 2021-03-02T16:23:16Z
Resource Version: 147313
Self Link: /apis/ops.kubedb.com/v1alpha1/namespaces/demo/mongodbopsrequests/mops-hscale-up-shard
UID: 982014fc-1655-44e7-946c-859626ae0247
Spec:
Database Ref:
Name: mg-sharding
Horizontal Scaling:
Config Server:
Replicas: 4
Mongos:
Replicas: 3
Shard:
Replicas: 4
Shards: 3
Type: HorizontalScaling
Status:
Conditions:
Last Transition Time: 2021-03-02T16:23:16Z
Message: MongoDB ops request is horizontally scaling database
Observed Generation: 1
Reason: HorizontalScaling
Status: True
Type: HorizontalScaling
Last Transition Time: 2021-03-02T16:25:31Z
Message: Successfully Horizontally Scaled Up Shard Replicas
Observed Generation: 1
Reason: ScaleUpShardReplicas
Status: True
Type: ScaleUpShardReplicas
Last Transition Time: 2021-03-02T16:33:07Z
Message: Successfully Horizontally Scaled Up Shard
Observed Generation: 1
Reason: ScaleUpShard
Status: True
Type: ScaleUpShard
Last Transition Time: 2021-03-02T16:34:35Z
Message: Successfully Horizontally Scaled Up ConfigServer
Observed Generation: 1
Reason: ScaleUpConfigServer
Status: True
Type: ScaleUpConfigServer
Last Transition Time: 2021-03-02T16:36:30Z
Message: Successfully Horizontally Scaled Mongos
Observed Generation: 1
Reason: ScaleMongos
Status: True
Type: ScaleMongos
Last Transition Time: 2021-03-02T16:36:30Z
Message: Successfully Horizontally Scaled MongoDB
Observed Generation: 1
Reason: Successful
Status: True
Type: Successful
Observed Generation: 1
Phase: Successful
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal PauseDatabase 13m KubeDB Ops-manager operator Pausing MongoDB demo/mg-sharding
Normal PauseDatabase 13m KubeDB Ops-manager operator Successfully paused MongoDB demo/mg-sharding
Normal ScaleUpShardReplicas 11m KubeDB Ops-manager operator Successfully Horizontally Scaled Up Shard Replicas
Normal ResumeDatabase 11m KubeDB Ops-manager operator Resuming MongoDB demo/mg-sharding
Normal ResumeDatabase 11m KubeDB Ops-manager operator Successfully resumed MongoDB demo/mg-sharding
Normal ScaleUpShardReplicas 11m KubeDB Ops-manager operator Successfully Horizontally Scaled Up Shard Replicas
Normal ScaleUpShardReplicas 11m KubeDB Ops-manager operator Successfully Horizontally Scaled Up Shard Replicas
Normal Progressing 8m20s KubeDB Ops-manager operator Successfully updated StatefulSets Resources
Normal Progressing 4m5s KubeDB Ops-manager operator Successfully updated StatefulSets Resources
Normal ScaleUpShard 3m59s KubeDB Ops-manager operator Successfully Horizontally Scaled Up Shard
Normal PauseDatabase 3m59s KubeDB Ops-manager operator Pausing MongoDB demo/mg-sharding
Normal PauseDatabase 3m59s KubeDB Ops-manager operator Successfully paused MongoDB demo/mg-sharding
Normal ScaleUpConfigServer 2m31s KubeDB Ops-manager operator Successfully Horizontally Scaled Up ConfigServer
Normal ScaleMongos 36s KubeDB Ops-manager operator Successfully Horizontally Scaled Mongos
Normal ResumeDatabase 36s KubeDB Ops-manager operator Resuming MongoDB demo/mg-sharding
Normal ResumeDatabase 36s KubeDB Ops-manager operator Successfully resumed MongoDB demo/mg-sharding
Normal Successful 36s KubeDB Ops-manager operator Successfully Horizontally Scaled Database
Verify Number of Shard and Shard Replicas
Now, we are going to verify the number of shards this database has from the MongoDB object, number of statefulsets it has,
$ kubectl get mongodb -n demo mg-sharding -o json | jq '.spec.shardTopology.shard.shards'
3
$ kubectl get sts -n demo
NAME READY AGE
mg-sharding-configsvr 4/4 66m
mg-sharding-mongos 3/3 64m
mg-sharding-shard0 4/4 66m
mg-sharding-shard1 4/4 66m
mg-sharding-shard2 4/4 12m
Now let’s connect to a mongos instance and run a mongodb internal command to check the number of shards,
$ kubectl exec -n demo mg-sharding-mongos-0 -- mongo admin -u root -p xBC-EwMFivFCgUlK --eval "sh.status()" --quiet
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId("603e5a4bec470e6b4197e10b")
}
shards:
{ "_id" : "shard0", "host" : "shard0/mg-sharding-shard0-0.mg-sharding-shard0-pods.demo.svc.cluster.local:27017,mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017,mg-sharding-shard0-2.mg-sharding-shard0-pods.demo.svc.cluster.local:27017,mg-sharding-shard0-3.mg-sharding-shard0-pods.demo.svc.cluster.local:27017", "state" : 1 }
{ "_id" : "shard1", "host" : "shard1/mg-sharding-shard1-0.mg-sharding-shard1-pods.demo.svc.cluster.local:27017,mg-sharding-shard1-1.mg-sharding-shard1-pods.demo.svc.cluster.local:27017,mg-sharding-shard1-2.mg-sharding-shard1-pods.demo.svc.cluster.local:27017,mg-sharding-shard1-3.mg-sharding-shard1-pods.demo.svc.cluster.local:27017", "state" : 1 }
{ "_id" : "shard2", "host" : "shard2/mg-sharding-shard2-0.mg-sharding-shard2-pods.demo.svc.cluster.local:27017,mg-sharding-shard2-1.mg-sharding-shard2-pods.demo.svc.cluster.local:27017,mg-sharding-shard2-2.mg-sharding-shard2-pods.demo.svc.cluster.local:27017,mg-sharding-shard2-3.mg-sharding-shard2-pods.demo.svc.cluster.local:27017", "state" : 1 }
active mongoses:
"4.2.3" : 3
autosplit:
Currently enabled: yes
balancer:
Currently enabled: yes
Currently running: no
Failed balancer rounds in last 5 attempts: 2
Last reported error: Couldn't get a connection within the time limit
Time of Reported error: Tue Mar 02 2021 16:17:53 GMT+0000 (UTC)
Migration Results for the last 24 hours:
No recent migrations
databases:
{ "_id" : "config", "primary" : "config", "partitioned" : true }
config.system.sessions
shard key: { "_id" : 1 }
unique: false
balancing: true
chunks:
shard0 1
{ "_id" : { "$minKey" : 1 } } -->> { "_id" : { "$maxKey" : 1 } } on : shard0 Timestamp(1, 0)
From all the above outputs we can see that the number of shards are 3.
Now, we are going to verify the number of replicas each shard has from the MongoDB object, number of pods the statefulset have,
$ kubectl get mongodb -n demo mg-sharding -o json | jq '.spec.shardTopology.shard.replicas'
4
$ kubectl get sts -n demo mg-sharding-shard0 -o json | jq '.spec.replicas'
4
Now let’s connect to a shard instance and run a mongodb internal command to check the number of replicas,
$ kubectl exec -n demo mg-sharding-shard0-0 -- mongo admin -u root -p xBC-EwMFivFCgUlK --eval "db.adminCommand( { replSetGetStatus : 1 } ).members" --quiet
[
{
"_id" : 0,
"name" : "mg-sharding-shard0-0.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 1464,
"optime" : {
"ts" : Timestamp(1614703143, 10),
"t" : NumberLong(2)
},
"optimeDate" : ISODate("2021-03-02T16:39:03Z"),
"syncingTo" : "mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"syncSourceHost" : "mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 1,
"infoMessage" : "",
"configVersion" : 4,
"self" : true,
"lastHeartbeatMessage" : ""
},
{
"_id" : 1,
"name" : "mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 1433,
"optime" : {
"ts" : Timestamp(1614703143, 10),
"t" : NumberLong(2)
},
"optimeDurable" : {
"ts" : Timestamp(1614703143, 10),
"t" : NumberLong(2)
},
"optimeDate" : ISODate("2021-03-02T16:39:03Z"),
"optimeDurableDate" : ISODate("2021-03-02T16:39:03Z"),
"lastHeartbeat" : ISODate("2021-03-02T16:39:07.800Z"),
"lastHeartbeatRecv" : ISODate("2021-03-02T16:39:08.087Z"),
"pingMs" : NumberLong(6),
"lastHeartbeatMessage" : "",
"syncingTo" : "",
"syncSourceHost" : "",
"syncSourceId" : -1,
"infoMessage" : "",
"electionTime" : Timestamp(1614701678, 2),
"electionDate" : ISODate("2021-03-02T16:14:38Z"),
"configVersion" : 4
},
{
"_id" : 2,
"name" : "mg-sharding-shard0-2.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 1433,
"optime" : {
"ts" : Timestamp(1614703143, 10),
"t" : NumberLong(2)
},
"optimeDurable" : {
"ts" : Timestamp(1614703143, 10),
"t" : NumberLong(2)
},
"optimeDate" : ISODate("2021-03-02T16:39:03Z"),
"optimeDurableDate" : ISODate("2021-03-02T16:39:03Z"),
"lastHeartbeat" : ISODate("2021-03-02T16:39:08.575Z"),
"lastHeartbeatRecv" : ISODate("2021-03-02T16:39:08.580Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncingTo" : "mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"syncSourceHost" : "mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 1,
"infoMessage" : "",
"configVersion" : 4
},
{
"_id" : 3,
"name" : "mg-sharding-shard0-3.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 905,
"optime" : {
"ts" : Timestamp(1614703143, 10),
"t" : NumberLong(2)
},
"optimeDurable" : {
"ts" : Timestamp(1614703143, 10),
"t" : NumberLong(2)
},
"optimeDate" : ISODate("2021-03-02T16:39:03Z"),
"optimeDurableDate" : ISODate("2021-03-02T16:39:03Z"),
"lastHeartbeat" : ISODate("2021-03-02T16:39:06.683Z"),
"lastHeartbeatRecv" : ISODate("2021-03-02T16:39:07.980Z"),
"pingMs" : NumberLong(10),
"lastHeartbeatMessage" : "",
"syncingTo" : "mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"syncSourceHost" : "mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 1,
"infoMessage" : "",
"configVersion" : 4
}
]
From all the above outputs we can see that the replicas of each shard has is 4.
Verify Number of ConfigServer Replicas
Now, we are going to verify the number of replicas this database has from the MongoDB object, number of pods the statefulset have,
$ kubectl get mongodb -n demo mg-sharding -o json | jq '.spec.shardTopology.configServer.replicas'
4
$ kubectl get sts -n demo mg-sharding-configsvr -o json | jq '.spec.replicas'
4
Now let’s connect to a mongodb instance and run a mongodb internal command to check the number of replicas,
$ kubectl exec -n demo mg-sharding-configsvr-0 -- mongo admin -u root -p xBC-EwMFivFCgUlK --eval "db.adminCommand( { replSetGetStatus : 1 } ).members" --quiet
[
{
"_id" : 0,
"name" : "mg-sharding-configsvr-0.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 1639,
"optime" : {
"ts" : Timestamp(1614703138, 2),
"t" : NumberLong(2)
},
"optimeDate" : ISODate("2021-03-02T16:38:58Z"),
"syncingTo" : "mg-sharding-configsvr-2.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"syncSourceHost" : "mg-sharding-configsvr-2.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 2,
"infoMessage" : "",
"configVersion" : 4,
"self" : true,
"lastHeartbeatMessage" : ""
},
{
"_id" : 1,
"name" : "mg-sharding-configsvr-1.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 1623,
"optime" : {
"ts" : Timestamp(1614703138, 2),
"t" : NumberLong(2)
},
"optimeDurable" : {
"ts" : Timestamp(1614703138, 2),
"t" : NumberLong(2)
},
"optimeDate" : ISODate("2021-03-02T16:38:58Z"),
"optimeDurableDate" : ISODate("2021-03-02T16:38:58Z"),
"lastHeartbeat" : ISODate("2021-03-02T16:38:58.979Z"),
"lastHeartbeatRecv" : ISODate("2021-03-02T16:38:59.291Z"),
"pingMs" : NumberLong(3),
"lastHeartbeatMessage" : "",
"syncingTo" : "",
"syncSourceHost" : "",
"syncSourceId" : -1,
"infoMessage" : "",
"electionTime" : Timestamp(1614701497, 2),
"electionDate" : ISODate("2021-03-02T16:11:37Z"),
"configVersion" : 4
},
{
"_id" : 2,
"name" : "mg-sharding-configsvr-2.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 1623,
"optime" : {
"ts" : Timestamp(1614703138, 2),
"t" : NumberLong(2)
},
"optimeDurable" : {
"ts" : Timestamp(1614703138, 2),
"t" : NumberLong(2)
},
"optimeDate" : ISODate("2021-03-02T16:38:58Z"),
"optimeDurableDate" : ISODate("2021-03-02T16:38:58Z"),
"lastHeartbeat" : ISODate("2021-03-02T16:38:58.885Z"),
"lastHeartbeatRecv" : ISODate("2021-03-02T16:39:00.188Z"),
"pingMs" : NumberLong(3),
"lastHeartbeatMessage" : "",
"syncingTo" : "mg-sharding-configsvr-1.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"syncSourceHost" : "mg-sharding-configsvr-1.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 1,
"infoMessage" : "",
"configVersion" : 4
},
{
"_id" : 3,
"name" : "mg-sharding-configsvr-3.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 296,
"optime" : {
"ts" : Timestamp(1614703138, 2),
"t" : NumberLong(2)
},
"optimeDurable" : {
"ts" : Timestamp(1614703138, 2),
"t" : NumberLong(2)
},
"optimeDate" : ISODate("2021-03-02T16:38:58Z"),
"optimeDurableDate" : ISODate("2021-03-02T16:38:58Z"),
"lastHeartbeat" : ISODate("2021-03-02T16:38:58.977Z"),
"lastHeartbeatRecv" : ISODate("2021-03-02T16:39:00.276Z"),
"pingMs" : NumberLong(1),
"lastHeartbeatMessage" : "",
"syncingTo" : "mg-sharding-configsvr-1.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"syncSourceHost" : "mg-sharding-configsvr-1.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 1,
"infoMessage" : "",
"configVersion" : 4
}
]
From all the above outputs we can see that the replicas of the configServer is 3. That means we have successfully scaled up the replicas of the MongoDB configServer replicas.
Verify Number of Mongos Replicas
Now, we are going to verify the number of replicas this database has from the MongoDB object, number of pods the statefulset have,
$ kubectl get mongodb -n demo mg-sharding -o json | jq '.spec.shardTopology.mongos.replicas'
3
$ kubectl get sts -n demo mg-sharding-mongos -o json | jq '.spec.replicas'
3
Now let’s connect to a mongodb instance and run a mongodb internal command to check the number of replicas,
$ kubectl exec -n demo mg-sharding-mongos-0 -- mongo admin -u root -p xBC-EwMFivFCgUlK --eval "sh.status()" --quiet
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId("603e5a4bec470e6b4197e10b")
}
shards:
{ "_id" : "shard0", "host" : "shard0/mg-sharding-shard0-0.mg-sharding-shard0-pods.demo.svc.cluster.local:27017,mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017,mg-sharding-shard0-2.mg-sharding-shard0-pods.demo.svc.cluster.local:27017,mg-sharding-shard0-3.mg-sharding-shard0-pods.demo.svc.cluster.local:27017", "state" : 1 }
{ "_id" : "shard1", "host" : "shard1/mg-sharding-shard1-0.mg-sharding-shard1-pods.demo.svc.cluster.local:27017,mg-sharding-shard1-1.mg-sharding-shard1-pods.demo.svc.cluster.local:27017,mg-sharding-shard1-2.mg-sharding-shard1-pods.demo.svc.cluster.local:27017,mg-sharding-shard1-3.mg-sharding-shard1-pods.demo.svc.cluster.local:27017", "state" : 1 }
{ "_id" : "shard2", "host" : "shard2/mg-sharding-shard2-0.mg-sharding-shard2-pods.demo.svc.cluster.local:27017,mg-sharding-shard2-1.mg-sharding-shard2-pods.demo.svc.cluster.local:27017,mg-sharding-shard2-2.mg-sharding-shard2-pods.demo.svc.cluster.local:27017,mg-sharding-shard2-3.mg-sharding-shard2-pods.demo.svc.cluster.local:27017", "state" : 1 }
active mongoses:
"4.2.3" : 3
autosplit:
Currently enabled: yes
balancer:
Currently enabled: yes
Currently running: no
Failed balancer rounds in last 5 attempts: 2
Last reported error: Couldn't get a connection within the time limit
Time of Reported error: Tue Mar 02 2021 16:17:53 GMT+0000 (UTC)
Migration Results for the last 24 hours:
No recent migrations
databases:
{ "_id" : "config", "primary" : "config", "partitioned" : true }
config.system.sessions
shard key: { "_id" : 1 }
unique: false
balancing: true
chunks:
shard0 1
{ "_id" : { "$minKey" : 1 } } -->> { "_id" : { "$maxKey" : 1 } } on : shard0 Timestamp(1, 0)
From all the above outputs we can see that the replicas of the mongos is 3. That means we have successfully scaled up the replicas of the MongoDB mongos replicas.
So, we have successfully scaled up all the components of the MongoDB database.
Scale Down
Here, we are going to scale down both the shard and their replicas to meet the desired number of replicas after scaling.
Create MongoDBOpsRequest
In order to scale down, we have to create a MongoDBOpsRequest CR with our configuration. Below is the YAML of the MongoDBOpsRequest CR that we are going to create,
apiVersion: ops.kubedb.com/v1alpha1
kind: MongoDBOpsRequest
metadata:
name: mops-hscale-down-shard
namespace: demo
spec:
type: HorizontalScaling
databaseRef:
name: mg-sharding
horizontalScaling:
shard:
shards: 2
replicas: 3
mongos:
replicas: 2
configServer:
replicas: 3
Here,
spec.databaseRef.namespecifies that we are performing horizontal scaling operation onmops-hscale-down-sharddatabase.spec.typespecifies that we are performingHorizontalScalingon our database.spec.horizontalScaling.shard.shardsspecifies the desired number of shards after scaling.spec.horizontalScaling.shard.replicasspecifies the desired number of replicas of each shard after scaling.spec.horizontalScaling.configServer.replicasspecifies the desired replicas after scaling.spec.horizontalScaling.mongos.replicasspecifies the desired replicas after scaling.
Note: If you don’t want to scale all the components together, you can only specify the components (shard, configServer and mongos) that you want to scale.
Let’s create the MongoDBOpsRequest CR we have shown above,
$ kubectl apply -f https://github.com/kubedb/docs/raw/v2023.06.19/docs/examples/mongodb/scaling/horizontal-scaling/mops-hscale-down-shard.yaml
mongodbopsrequest.ops.kubedb.com/mops-hscale-down-shard created
Verify scaling down is successful
If everything goes well, KubeDB Ops-manager operator will update the shards and replicas MongoDB object and related StatefulSets and Pods.
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-hscale-down-shard HorizontalScaling Successful 81s
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 scale down the the database.
$ kubectl describe mongodbopsrequest -n demo mops-hscale-down-shard
Name: mops-hscale-down-shard
Namespace: demo
Labels: <none>
Annotations: <none>
API Version: ops.kubedb.com/v1alpha1
Kind: MongoDBOpsRequest
Metadata:
Creation Timestamp: 2021-03-02T16:41:11Z
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:databaseRef:
.:
f:name:
f:horizontalScaling:
.:
f:configServer:
.:
f:replicas:
f:mongos:
.:
f:replicas:
f:shard:
.:
f:replicas:
f:shards:
f:type:
Manager: kubectl-client-side-apply
Operation: Update
Time: 2021-03-02T16:41:11Z
API Version: ops.kubedb.com/v1alpha1
Fields Type: FieldsV1
fieldsV1:
f:status:
.:
f:conditions:
f:observedGeneration:
f:phase:
Manager: kubedb-enterprise
Operation: Update
Time: 2021-03-02T16:41:11Z
Resource Version: 149077
Self Link: /apis/ops.kubedb.com/v1alpha1/namespaces/demo/mongodbopsrequests/mops-hscale-down-shard
UID: 0f83c457-9498-4144-a397-226141851751
Spec:
Database Ref:
Name: mg-sharding
Horizontal Scaling:
Config Server:
Replicas: 3
Mongos:
Replicas: 2
Shard:
Replicas: 3
Shards: 2
Type: HorizontalScaling
Status:
Conditions:
Last Transition Time: 2021-03-02T16:41:11Z
Message: MongoDB ops request is horizontally scaling database
Observed Generation: 1
Reason: HorizontalScaling
Status: True
Type: HorizontalScaling
Last Transition Time: 2021-03-02T16:42:11Z
Message: Successfully Horizontally Scaled Down Shard Replicas
Observed Generation: 1
Reason: ScaleDownShardReplicas
Status: True
Type: ScaleDownShardReplicas
Last Transition Time: 2021-03-02T16:42:12Z
Message: Successfully started mongodb load balancer
Observed Generation: 1
Reason: StartingBalancer
Status: True
Type: StartingBalancer
Last Transition Time: 2021-03-02T16:43:03Z
Message: Successfully Horizontally Scaled Down Shard
Observed Generation: 1
Reason: ScaleDownShard
Status: True
Type: ScaleDownShard
Last Transition Time: 2021-03-02T16:43:24Z
Message: Successfully Horizontally Scaled Down ConfigServer
Observed Generation: 1
Reason: ScaleDownConfigServer
Status: True
Type: ScaleDownConfigServer
Last Transition Time: 2021-03-02T16:43:34Z
Message: Successfully Horizontally Scaled Mongos
Observed Generation: 1
Reason: ScaleMongos
Status: True
Type: ScaleMongos
Last Transition Time: 2021-03-02T16:43:34Z
Message: Successfully Horizontally Scaled MongoDB
Observed Generation: 1
Reason: Successful
Status: True
Type: Successful
Observed Generation: 1
Phase: Successful
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal PauseDatabase 6m29s KubeDB Ops-manager operator Pausing MongoDB demo/mg-sharding
Normal PauseDatabase 6m29s KubeDB Ops-manager operator Successfully paused MongoDB demo/mg-sharding
Normal ScaleDownShardReplicas 5m29s KubeDB Ops-manager operator Successfully Horizontally Scaled Down Shard Replicas
Normal StartingBalancer 5m29s KubeDB Ops-manager operator Starting Balancer
Normal StartingBalancer 5m28s KubeDB Ops-manager operator Successfully Started Balancer
Normal ScaleDownShard 4m37s KubeDB Ops-manager operator Successfully Horizontally Scaled Down Shard
Normal ScaleDownConfigServer 4m16s KubeDB Ops-manager operator Successfully Horizontally Scaled Down ConfigServer
Normal ScaleMongos 4m6s KubeDB Ops-manager operator Successfully Horizontally Scaled Mongos
Normal ResumeDatabase 4m6s KubeDB Ops-manager operator Resuming MongoDB demo/mg-sharding
Normal ResumeDatabase 4m6s KubeDB Ops-manager operator Successfully resumed MongoDB demo/mg-sharding
Normal Successful 4m6s KubeDB Ops-manager operator Successfully Horizontally Scaled Database
Verify Number of Shard and Shard Replicas
Now, we are going to verify the number of shards this database has from the MongoDB object, number of statefulsets it has,
$ kubectl get mongodb -n demo mg-sharding -o json | jq '.spec.shardTopology.shard.shards'
2
$ kubectl get sts -n demo
NAME READY AGE
mg-sharding-configsvr 3/3 77m
mg-sharding-mongos 2/2 75m
mg-sharding-shard0 3/3 77m
mg-sharding-shard1 3/3 77m
Now let’s connect to a mongos instance and run a mongodb internal command to check the number of shards,
$ kubectl exec -n demo mg-sharding-mongos-0 -- mongo admin -u root -p xBC-EwMFivFCgUlK --eval "sh.status()" --quiet
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId("603e5a4bec470e6b4197e10b")
}
shards:
{ "_id" : "shard0", "host" : "shard0/mg-sharding-shard0-0.mg-sharding-shard0-pods.demo.svc.cluster.local:27017,mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017,mg-sharding-shard0-2.mg-sharding-shard0-pods.demo.svc.cluster.local:27017", "state" : 1 }
{ "_id" : "shard1", "host" : "shard1/mg-sharding-shard1-0.mg-sharding-shard1-pods.demo.svc.cluster.local:27017,mg-sharding-shard1-1.mg-sharding-shard1-pods.demo.svc.cluster.local:27017,mg-sharding-shard1-2.mg-sharding-shard1-pods.demo.svc.cluster.local:27017", "state" : 1 }
active mongoses:
"4.2.3" : 2
autosplit:
Currently enabled: yes
balancer:
Currently enabled: yes
Currently running: no
Failed balancer rounds in last 5 attempts: 2
Last reported error: Couldn't get a connection within the time limit
Time of Reported error: Tue Mar 02 2021 16:17:53 GMT+0000 (UTC)
Migration Results for the last 24 hours:
No recent migrations
databases:
{ "_id" : "config", "primary" : "config", "partitioned" : true }
config.system.sessions
shard key: { "_id" : 1 }
unique: false
balancing: true
chunks:
shard0 1
{ "_id" : { "$minKey" : 1 } } -->> { "_id" : { "$maxKey" : 1 } } on : shard0 Timestamp(1, 0)
From all the above outputs we can see that the number of shards are 2.
Now, we are going to verify the number of replicas each shard has from the MongoDB object, number of pods the statefulset have,
$ kubectl get mongodb -n demo mg-sharding -o json | jq '.spec.shardTopology.shard.replicas'
3
$ kubectl get sts -n demo mg-sharding-shard0 -o json | jq '.spec.replicas'
3
Now let’s connect to a shard instance and run a mongodb internal command to check the number of replicas,
$ kubectl exec -n demo mg-sharding-shard0-0 -- mongo admin -u root -p xBC-EwMFivFCgUlK --eval "db.adminCommand( { replSetGetStatus : 1 } ).members" --quiet
[
{
"_id" : 0,
"name" : "mg-sharding-shard0-0.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 2096,
"optime" : {
"ts" : Timestamp(1614703771, 1),
"t" : NumberLong(2)
},
"optimeDate" : ISODate("2021-03-02T16:49:31Z"),
"syncingTo" : "mg-sharding-shard0-2.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"syncSourceHost" : "mg-sharding-shard0-2.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 2,
"infoMessage" : "",
"configVersion" : 5,
"self" : true,
"lastHeartbeatMessage" : ""
},
{
"_id" : 1,
"name" : "mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 2065,
"optime" : {
"ts" : Timestamp(1614703771, 1),
"t" : NumberLong(2)
},
"optimeDurable" : {
"ts" : Timestamp(1614703771, 1),
"t" : NumberLong(2)
},
"optimeDate" : ISODate("2021-03-02T16:49:31Z"),
"optimeDurableDate" : ISODate("2021-03-02T16:49:31Z"),
"lastHeartbeat" : ISODate("2021-03-02T16:49:39.092Z"),
"lastHeartbeatRecv" : ISODate("2021-03-02T16:49:40.074Z"),
"pingMs" : NumberLong(18),
"lastHeartbeatMessage" : "",
"syncingTo" : "",
"syncSourceHost" : "",
"syncSourceId" : -1,
"infoMessage" : "",
"electionTime" : Timestamp(1614701678, 2),
"electionDate" : ISODate("2021-03-02T16:14:38Z"),
"configVersion" : 5
},
{
"_id" : 2,
"name" : "mg-sharding-shard0-2.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 2065,
"optime" : {
"ts" : Timestamp(1614703771, 1),
"t" : NumberLong(2)
},
"optimeDurable" : {
"ts" : Timestamp(1614703771, 1),
"t" : NumberLong(2)
},
"optimeDate" : ISODate("2021-03-02T16:49:31Z"),
"optimeDurableDate" : ISODate("2021-03-02T16:49:31Z"),
"lastHeartbeat" : ISODate("2021-03-02T16:49:38.712Z"),
"lastHeartbeatRecv" : ISODate("2021-03-02T16:49:39.885Z"),
"pingMs" : NumberLong(4),
"lastHeartbeatMessage" : "",
"syncingTo" : "mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"syncSourceHost" : "mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 1,
"infoMessage" : "",
"configVersion" : 5
}
]
From all the above outputs we can see that the replicas of each shard has is 3.
Verify Number of ConfigServer Replicas
Now, we are going to verify the number of replicas this database has from the MongoDB object, number of pods the statefulset have,
$ kubectl get mongodb -n demo mg-sharding -o json | jq '.spec.shardTopology.configServer.replicas'
3
$ kubectl get sts -n demo mg-sharding-configsvr -o json | jq '.spec.replicas'
3
Now let’s connect to a mongodb instance and run a mongodb internal command to check the number of replicas,
$ kubectl exec -n demo mg-sharding-configsvr-0 -- mongo admin -u root -p xBC-EwMFivFCgUlK --eval "db.adminCommand( { replSetGetStatus : 1 } ).members" --quiet
[
{
"_id" : 0,
"name" : "mg-sharding-configsvr-0.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 2345,
"optime" : {
"ts" : Timestamp(1614703841, 1),
"t" : NumberLong(2)
},
"optimeDate" : ISODate("2021-03-02T16:50:41Z"),
"syncingTo" : "mg-sharding-configsvr-1.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"syncSourceHost" : "mg-sharding-configsvr-1.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 1,
"infoMessage" : "",
"configVersion" : 5,
"self" : true,
"lastHeartbeatMessage" : ""
},
{
"_id" : 1,
"name" : "mg-sharding-configsvr-1.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 2329,
"optime" : {
"ts" : Timestamp(1614703841, 1),
"t" : NumberLong(2)
},
"optimeDurable" : {
"ts" : Timestamp(1614703841, 1),
"t" : NumberLong(2)
},
"optimeDate" : ISODate("2021-03-02T16:50:41Z"),
"optimeDurableDate" : ISODate("2021-03-02T16:50:41Z"),
"lastHeartbeat" : ISODate("2021-03-02T16:50:45.874Z"),
"lastHeartbeatRecv" : ISODate("2021-03-02T16:50:44.194Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncingTo" : "",
"syncSourceHost" : "",
"syncSourceId" : -1,
"infoMessage" : "",
"electionTime" : Timestamp(1614701497, 2),
"electionDate" : ISODate("2021-03-02T16:11:37Z"),
"configVersion" : 5
},
{
"_id" : 2,
"name" : "mg-sharding-configsvr-2.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 2329,
"optime" : {
"ts" : Timestamp(1614703841, 1),
"t" : NumberLong(2)
},
"optimeDurable" : {
"ts" : Timestamp(1614703841, 1),
"t" : NumberLong(2)
},
"optimeDate" : ISODate("2021-03-02T16:50:41Z"),
"optimeDurableDate" : ISODate("2021-03-02T16:50:41Z"),
"lastHeartbeat" : ISODate("2021-03-02T16:50:45.778Z"),
"lastHeartbeatRecv" : ISODate("2021-03-02T16:50:46.091Z"),
"pingMs" : NumberLong(1),
"lastHeartbeatMessage" : "",
"syncingTo" : "mg-sharding-configsvr-1.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"syncSourceHost" : "mg-sharding-configsvr-1.mg-sharding-configsvr-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 1,
"infoMessage" : "",
"configVersion" : 5
}
]
From all the above outputs we can see that the replicas of the configServer is 3. That means we have successfully scaled down the replicas of the MongoDB configServer replicas.
Verify Number of Mongos Replicas
Now, we are going to verify the number of replicas this database has from the MongoDB object, number of pods the statefulset have,
$ kubectl get mongodb -n demo mg-sharding -o json | jq '.spec.shardTopology.mongos.replicas'
2
$ kubectl get sts -n demo mg-sharding-mongos -o json | jq '.spec.replicas'
2
Now let’s connect to a mongodb instance and run a mongodb internal command to check the number of replicas,
$ kubectl exec -n demo mg-sharding-mongos-0 -- mongo admin -u root -p xBC-EwMFivFCgUlK --eval "sh.status()" --quiet
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId("603e5a4bec470e6b4197e10b")
}
shards:
{ "_id" : "shard0", "host" : "shard0/mg-sharding-shard0-0.mg-sharding-shard0-pods.demo.svc.cluster.local:27017,mg-sharding-shard0-1.mg-sharding-shard0-pods.demo.svc.cluster.local:27017,mg-sharding-shard0-2.mg-sharding-shard0-pods.demo.svc.cluster.local:27017", "state" : 1 }
{ "_id" : "shard1", "host" : "shard1/mg-sharding-shard1-0.mg-sharding-shard1-pods.demo.svc.cluster.local:27017,mg-sharding-shard1-1.mg-sharding-shard1-pods.demo.svc.cluster.local:27017,mg-sharding-shard1-2.mg-sharding-shard1-pods.demo.svc.cluster.local:27017", "state" : 1 }
active mongoses:
"4.2.3" : 2
autosplit:
Currently enabled: yes
balancer:
Currently enabled: yes
Currently running: no
Failed balancer rounds in last 5 attempts: 2
Last reported error: Couldn't get a connection within the time limit
Time of Reported error: Tue Mar 02 2021 16:17:53 GMT+0000 (UTC)
Migration Results for the last 24 hours:
No recent migrations
databases:
{ "_id" : "config", "primary" : "config", "partitioned" : true }
config.system.sessions
shard key: { "_id" : 1 }
unique: false
balancing: true
chunks:
shard0 1
{ "_id" : { "$minKey" : 1 } } -->> { "_id" : { "$maxKey" : 1 } } on : shard0 Timestamp(1, 0)
From all the above outputs we can see that the replicas of the mongos is 2. That means we have successfully scaled down the replicas of the MongoDB mongos replicas.
So, we have successfully scaled down all the components of the MongoDB database.
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-vscale-up-shard mops-vscale-down-shard