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KubeDB - MongoDB ReplicaSet with Hidden-node
This tutorial will show you how to use KubeDB to run a MongoDB ReplicaSet with hidden-node.
Before You Begin
Before proceeding:
Read mongodb hidden-node concept to get the concept about MongoDB Hidden node.
You need to have a Kubernetes cluster, and the kubectl command-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.
Now, install KubeDB cli on your workstation and KubeDB operator in your cluster following the steps here.
To keep things isolated, this tutorial uses a separate namespace called
demothroughout this tutorial. Run the following command to prepare your cluster for this tutorial:$ kubectl create ns demo namespace/demo created
Note: The yaml files used in this tutorial are stored in docs/examples/mongodb folder in GitHub repository kubedb/docs.
Deploy MongoDB ReplicaSet with Hidden-node
To deploy a MongoDB ReplicaSet, user have to specify spec.replicaSet option in Mongodb CRD.
The following is an example of a Mongodb object which creates MongoDB ReplicaSet of three members.
apiVersion: kubedb.com/v1
kind: MongoDB
metadata:
name: mongo-rs-hid
namespace: demo
spec:
version: "percona-7.0.4"
replicaSet:
name: "replicaset"
podTemplate:
spec:
containers:
- name: mongo
resources:
requests:
cpu: "600m"
memory: "600Mi"
replicas: 3
storageEngine: inMemory
storageType: Ephemeral
ephemeralStorage:
sizeLimit: "900Mi"
hidden:
podTemplate:
spec:
resources:
requests:
cpu: "400m"
memory: "400Mi"
replicas: 2
storage:
storageClassName: "standard"
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 2Gi
deletionPolicy: WipeOut
Note: inMemory databases are only allowed for Percona variations of mongodb
$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.11.18/docs/examples/mongodb/hidden-node/replicaset.yaml
mongodb.kubedb.com/mongo-rs-hid created
Here,
spec.replicaSetrepresents the configuration for replicaset.namedenotes the name of mongodb replicaset.
spec.keyFileSecret(optional) is a secret name that contains keyfile (a random string)againstkey.txtkey. Each mongod instances in the replica set andshardTopologyuses the contents of the keyfile as the shared password for authenticating other members in the replicaset. Only mongod instances with the correct keyfile can join the replica set. User can provide thekeyFileSecretby creating a secret with keykey.txt. See here to create the string forkeyFileSecret. IfkeyFileSecretis not given, KubeDB operator will generate akeyFileSecretitself.spec.replicasdenotes the number of general members inrs0mongodb replicaset.spec.podTemplatedenotes specifications of all the 3 general replicaset members.spec.storageEngineis set to inMemory, &spec.storageTypeto ephemeral.spec.ephemeralStorageholds the emptyDir volume specifications. This storage spec will be passed to the PetSet created by KubeDB operator to run database pods. So, each members will have a pod of this ephemeral storage configuration.spec.hiddendenotes hidden-node spec of the deployed MongoDB CRD. There are four fields under it :spec.hidden.podTemplateholds the hidden-node podSpec.nullvalue of it, instructs kubedb operator to use the default hidden-node podTemplate.spec.hidden.configSecretis an optional field to provide custom configuration file for database (i.e mongod.cnf). If specified, this file will be used as configuration file otherwise default configuration file will be used.spec.hidden.replicasholds the number of hidden-node in the replica set.spec.hidden.storagespecifies the StorageClass of PVC dynamically allocated to store data for these hidden-nodes. This storage spec will be passed to the PetSet created by KubeDB operator to run database pods. So, each members will have a pod of this storage configuration. You can specify any StorageClass available in your cluster with appropriate resource requests.
KubeDB operator watches for MongoDB objects using Kubernetes api. When a MongoDB object is created, KubeDB operator will create two new PetSets (one for replicas & one for hidden-nodes) and a Service with the matching MongoDB object name. This service will always point to the primary of the replicaset. KubeDB operator will also create a governing service for the pods of those two PetSets with the name <mongodb-name>-pods.
$ kubectl dba describe mg -n demo mongo-rs-hid
Name: mongo-rs-hid
Namespace: demo
CreationTimestamp: Mon, 31 Oct 2022 11:03:50 +0600
Labels: <none>
Annotations: kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"kubedb.com/v1","kind":"MongoDB","metadata":{"annotations":{},"name":"mongo-rs-hid","namespace":"demo"},"spec":{"ephemeralStorage":...
Replicas: 3 total
Status: Ready
StorageType: Ephemeral
No volumes.
Paused: false
Halted: false
Termination Policy: WipeOut
PetSet:
Name: mongo-rs-hid
CreationTimestamp: Mon, 31 Oct 2022 11:03:50 +0600
Labels: app.kubernetes.io/component=database
app.kubernetes.io/instance=mongo-rs-hid
app.kubernetes.io/managed-by=kubedb.com
app.kubernetes.io/name=mongodbs.kubedb.com
mongodb.kubedb.com/node.type=replica
Annotations: <none>
Replicas: 824644499032 desired | 3 total
Pods Status: 3 Running / 0 Waiting / 0 Succeeded / 0 Failed
PetSet:
Name: mongo-rs-hid-hidden
CreationTimestamp: Mon, 31 Oct 2022 11:04:50 +0600
Labels: app.kubernetes.io/component=database
app.kubernetes.io/instance=mongo-rs-hid
app.kubernetes.io/managed-by=kubedb.com
app.kubernetes.io/name=mongodbs.kubedb.com
mongodb.kubedb.com/node.type=hidden
Annotations: <none>
Replicas: 824646223576 desired | 2 total
Pods Status: 2 Running / 0 Waiting / 0 Succeeded / 0 Failed
Service:
Name: mongo-rs-hid
Labels: app.kubernetes.io/component=database
app.kubernetes.io/instance=mongo-rs-hid
app.kubernetes.io/managed-by=kubedb.com
app.kubernetes.io/name=mongodbs.kubedb.com
Annotations: <none>
Type: ClusterIP
IP: 10.96.197.33
Port: primary 27017/TCP
TargetPort: db/TCP
Endpoints: 10.244.0.53:27017
Service:
Name: mongo-rs-hid-pods
Labels: app.kubernetes.io/component=database
app.kubernetes.io/instance=mongo-rs-hid
app.kubernetes.io/managed-by=kubedb.com
app.kubernetes.io/name=mongodbs.kubedb.com
Annotations: <none>
Type: ClusterIP
IP: None
Port: db 27017/TCP
TargetPort: db/TCP
Endpoints: 10.244.0.53:27017,10.244.0.54:27017,10.244.0.55:27017 + 2 more...
Auth Secret:
Name: mongo-rs-hid-auth
Labels: app.kubernetes.io/component=database
app.kubernetes.io/instance=mongo-rs-hid
app.kubernetes.io/managed-by=kubedb.com
app.kubernetes.io/name=mongodbs.kubedb.com
Annotations: <none>
Type: kubernetes.io/basic-auth
Data:
password: 16 bytes
username: 4 bytes
AppBinding:
Metadata:
Annotations:
kubectl.kubernetes.io/last-applied-configuration: {"apiVersion":"kubedb.com/v1","kind":"MongoDB","metadata":{"annotations":{},"name":"mongo-rs-hid","namespace":"demo"},"spec":{"ephemeralStorage":{"sizeLimit":"900Mi"},"hidden":{"podTemplate":{"spec":{"resources":{"requests":{"cpu":"400m","memory":"400Mi"}}}},"replicas":2,"storage":{"accessModes":["ReadWriteOnce"],"resources":{"requests":{"storage":"2Gi"}},"storageClassName":"standard"}},"podTemplate":{"spec":{"resources":{"requests":{"cpu":"600m","memory":"600Mi"}}}},"replicaSet":{"name":"replicaset"},"replicas":3,"storageEngine":"inMemory","storageType":"Ephemeral","deletionPolicy":"WipeOut","version":"percona-7.0.4"}}
Creation Timestamp: 2022-10-31T05:05:38Z
Labels:
app.kubernetes.io/component: database
app.kubernetes.io/instance: mongo-rs-hid
app.kubernetes.io/managed-by: kubedb.com
app.kubernetes.io/name: mongodbs.kubedb.com
Name: mongo-rs-hid
Namespace: demo
Spec:
Client Config:
Service:
Name: mongo-rs-hid
Port: 27017
Scheme: mongodb
Parameters:
API Version: config.kubedb.com/v1alpha1
Kind: MongoConfiguration
Replica Sets:
host-0: replicaset/mongo-rs-hid-0.mongo-rs-hid-pods.demo.svc:27017,mongo-rs-hid-1.mongo-rs-hid-pods.demo.svc:27017,mongo-rs-hid-2.mongo-rs-hid-pods.demo.svc:27017,mongo-rs-hid-hidden-0.mongo-rs-hid-pods.demo.svc:27017,mongo-rs-hid-hidden-1.mongo-rs-hid-pods.demo.svc:27017
Stash:
Addon:
Backup Task:
Name: mongodb-backup-4.4.6
Restore Task:
Name: mongodb-restore-4.4.6
Secret:
Name: mongo-rs-hid-auth
Type: kubedb.com/mongodb
Version: 7.0.4
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal PhaseChanged 12m MongoDB operator Phase changed from to Provisioning.
Normal Successful 12m MongoDB operator Successfully created governing service
Normal Successful 12m MongoDB operator Successfully created Primary Service
Normal Successful 11m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid
Normal Successful 11m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid
Normal Successful 11m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid
Normal Successful 11m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid
Normal Successful 11m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid
Normal Successful 11m MongoDB operator Successfully patched MongoDB
Normal Successful 11m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid-hidden
Normal Successful 11m MongoDB operator Successfully patched MongoDB
Normal Successful 11m MongoDB operator Successfully created appbinding
Normal Successful 11m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid
Normal Successful 11m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid-hidden
Normal Successful 11m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid
Normal PhaseChanged 11m MongoDB operator Phase changed from Provisioning to Ready.
Normal Successful 11m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid
Normal Successful 11m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid-hidden
Normal Successful 11m MongoDB operator Successfully patched MongoDB
Normal Successful 7m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid
Normal Successful 7m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid-hidden
Normal Successful 7m MongoDB operator Successfully patched MongoDB
Normal Successful 7m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid
Normal Successful 7m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid-hidden
Normal Successful 7m MongoDB operator Successfully patched MongoDB
Normal Successful 7m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid
Normal Successful 7m MongoDB operator Successfully patched PetSet demo/mongo-rs-hid-hidden
Normal Successful 7m MongoDB operator Successfully patched MongoDB
$ kubectl get petset -n demo
NAME READY AGE
mongo-rs-hid 3/3 13m
mongo-rs-hid-hidden 2/2 12m
$ kubectl get pvc -n demo
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
datadir-mongo-rs-hid-hidden-0 Bound pvc-e8c2a3b3-0c47-453f-8a5a-40d7dcb5b4d7 2Gi RWO standard 13m
datadir-mongo-rs-hid-hidden-1 Bound pvc-7b752799-b6b9-43cf-9aa7-d39a2577216c 2Gi RWO standard 13m
$ kubectl get pv -n demo
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pvc-7b752799-b6b9-43cf-9aa7-d39a2577216c 2Gi RWO Delete Bound demo/datadir-mongo-rs-hid-hidden-1 standard 13m
pvc-e8c2a3b3-0c47-453f-8a5a-40d7dcb5b4d7 2Gi RWO Delete Bound demo/datadir-mongo-rs-hid-hidden-0 standard 13m
$ kubectl get service -n demo
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
mongo-rs-hid ClusterIP 10.96.197.33 <none> 27017/TCP 14m
mongo-rs-hid-pods ClusterIP None <none> 27017/TCP 14m
KubeDB operator sets the status.phase to Ready once the database is successfully created. Run the following command to see the modified MongoDB object:
$ kubectl get mg -n demo mongo-rs-hid -o yaml
apiVersion: kubedb.com/v1
kind: MongoDB
metadata:
annotations:
kubectl.kubernetes.io/last-applied-configuration: |
{"apiVersion":"kubedb.com/v1","kind":"MongoDB","metadata":{"annotations":{},"name":"mongo-rs-hid","namespace":"demo"},"spec":{"ephemeralStorage":{"sizeLimit":"900Mi"},"hidden":{"podTemplate":{"spec":{"resources":{"requests":{"cpu":"400m","memory":"400Mi"}}}},"replicas":2,"storage":{"accessModes":["ReadWriteOnce"],"resources":{"requests":{"storage":"2Gi"}},"storageClassName":"standard"}},"podTemplate":{"spec":{"resources":{"requests":{"cpu":"600m","memory":"600Mi"}}}},"replicaSet":{"name":"replicaset"},"replicas":3,"storageEngine":"inMemory","storageType":"Ephemeral","deletionPolicy":"WipeOut","version":"percona-7.0.4"}}
creationTimestamp: "2022-10-31T05:03:50Z"
finalizers:
- kubedb.com
generation: 3
name: mongo-rs-hid
namespace: demo
resourceVersion: "716264"
uid: 428fa2bd-db5a-4bf5-a4ad-174fd0d7ade2
spec:
allowedSchemas:
namespaces:
from: Same
authSecret:
name: mongo-rs-hid-auth
autoOps: {}
clusterAuthMode: keyFile
ephemeralStorage:
sizeLimit: 900Mi
healthChecker:
failureThreshold: 1
periodSeconds: 10
timeoutSeconds: 10
hidden:
podTemplate:
controller: {}
metadata: {}
spec:
resources:
limits:
memory: 400Mi
requests:
cpu: 400m
memory: 400Mi
replicas: 2
storage:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 2Gi
storageClassName: standard
keyFileSecret:
name: mongo-rs-hid-key
podTemplate:
controller: {}
metadata: {}
spec:
resources:
limits:
memory: 600Mi
requests:
cpu: 600m
memory: 600Mi
serviceAccountName: mongo-rs-hid
replicaSet:
name: replicaset
replicas: 3
sslMode: disabled
storageEngine: inMemory
storageType: Ephemeral
deletionPolicy: WipeOut
version: percona-7.0.4
status:
conditions:
- lastTransitionTime: "2022-10-31T05:03:50Z"
message: 'The KubeDB operator has started the provisioning of MongoDB: demo/mongo-rs-hid'
reason: DatabaseProvisioningStartedSuccessfully
status: "True"
type: ProvisioningStarted
- lastTransitionTime: "2022-10-31T05:05:38Z"
message: All desired replicas are ready.
reason: AllReplicasReady
status: "True"
type: ReplicaReady
- lastTransitionTime: "2022-10-31T05:05:00Z"
message: 'The MongoDB: demo/mongo-rs-hid is accepting client requests.'
observedGeneration: 3
reason: DatabaseAcceptingConnectionRequest
status: "True"
type: AcceptingConnection
- lastTransitionTime: "2022-10-31T05:05:00Z"
message: 'The MongoDB: demo/mongo-rs-hid is ready.'
observedGeneration: 3
reason: ReadinessCheckSucceeded
status: "True"
type: Ready
- lastTransitionTime: "2022-10-31T05:05:38Z"
message: 'The MongoDB: demo/mongo-rs-hid is successfully provisioned.'
observedGeneration: 3
reason: DatabaseSuccessfullyProvisioned
status: "True"
type: Provisioned
observedGeneration: 3
phase: Ready
Please note that KubeDB operator has created a new Secret called mongo-rs-hid-auth (format: {mongodb-object-name}-auth) for storing the password for mongodb superuser. This secret contains a username key which contains the username for MongoDB superuser and a password key which contains the password for MongoDB superuser.
If you want to use custom or existing secret please specify that when creating the MongoDB object using spec.authSecret.name. While creating this secret manually, make sure the secret contains these two keys containing data username and password. For more details, please see here.
Redundancy and Data Availability
Now, you can connect to this database through mongo-rs-hid. In this tutorial, we will insert document on the primary member, and we will see if the data becomes available on secondary members.
At first, insert data inside primary member rs0:PRIMARY.
$ kubectl get secrets -n demo mongo-rs-hid-auth -o jsonpath='{.data.\username}' | base64 -d
root
$ kubectl get secrets -n demo mongo-rs-hid-auth -o jsonpath='{.data.\password}' | base64 -d
OX4yb!IFm;~yAHkD
$ kubectl exec -it mongo-rs-hid-0 -n demo bash
bash-4.4$ mongo admin -u root -p 'OX4yb!IFm;~yAHkD'
Percona Server for MongoDB shell version v7.0.4-11
connecting to: mongodb://127.0.0.1:27017/?compressors=disabled&gssapiServiceName=mongodb
Implicit session: session { "id" : UUID("11890d64-37da-43dd-acb6-0f36a3678875") }
Percona Server for MongoDB server version: v7.0.4-11
Welcome to the Percona Server for MongoDB shell.
For interactive help, type "help".
For more comprehensive documentation, see
https://www.percona.com/doc/percona-server-for-mongodb
Questions? Try the support group
https://www.percona.com/forums/questions-discussions/percona-server-for-mongodb
replicaset:PRIMARY>
replicaset:PRIMARY>
replicaset:PRIMARY> rs.status()
{
"set" : "replicaset",
"date" : ISODate("2022-10-31T05:25:19.148Z"),
"myState" : 1,
"term" : NumberLong(1),
"syncSourceHost" : "",
"syncSourceId" : -1,
"heartbeatIntervalMillis" : NumberLong(2000),
"majorityVoteCount" : 3,
"writeMajorityCount" : 3,
"votingMembersCount" : 5,
"writableVotingMembersCount" : 5,
"optimes" : {
"lastCommittedOpTime" : {
"ts" : Timestamp(1667193912, 1),
"t" : NumberLong(1)
},
"lastCommittedWallTime" : ISODate("2022-10-31T05:25:12.590Z"),
"readConcernMajorityOpTime" : {
"ts" : Timestamp(1667193912, 1),
"t" : NumberLong(1)
},
"readConcernMajorityWallTime" : ISODate("2022-10-31T05:25:12.590Z"),
"appliedOpTime" : {
"ts" : Timestamp(1667193912, 1),
"t" : NumberLong(1)
},
"durableOpTime" : {
"ts" : Timestamp(1667193912, 1),
"t" : NumberLong(1)
},
"lastAppliedWallTime" : ISODate("2022-10-31T05:25:12.590Z"),
"lastDurableWallTime" : ISODate("2022-10-31T05:25:12.590Z")
},
"lastStableRecoveryTimestamp" : Timestamp(1667193912, 1),
"electionCandidateMetrics" : {
"lastElectionReason" : "electionTimeout",
"lastElectionDate" : ISODate("2022-10-31T05:04:02.548Z"),
"electionTerm" : NumberLong(1),
"lastCommittedOpTimeAtElection" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"lastSeenOpTimeAtElection" : {
"ts" : Timestamp(1667192642, 1),
"t" : NumberLong(-1)
},
"numVotesNeeded" : 1,
"priorityAtElection" : 1,
"electionTimeoutMillis" : NumberLong(10000),
"newTermStartDate" : ISODate("2022-10-31T05:04:02.552Z"),
"wMajorityWriteAvailabilityDate" : ISODate("2022-10-31T05:04:02.553Z")
},
"members" : [
{
"_id" : 0,
"name" : "mongo-rs-hid-0.mongo-rs-hid-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 1287,
"optime" : {
"ts" : Timestamp(1667193912, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2022-10-31T05:25:12Z"),
"syncSourceHost" : "",
"syncSourceId" : -1,
"infoMessage" : "",
"electionTime" : Timestamp(1667192642, 2),
"electionDate" : ISODate("2022-10-31T05:04:02Z"),
"configVersion" : 5,
"configTerm" : 1,
"self" : true,
"lastHeartbeatMessage" : ""
},
{
"_id" : 1,
"name" : "mongo-rs-hid-1.mongo-rs-hid-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 1257,
"optime" : {
"ts" : Timestamp(1667193912, 1),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1667193912, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2022-10-31T05:25:12Z"),
"optimeDurableDate" : ISODate("2022-10-31T05:25:12Z"),
"lastHeartbeat" : ISODate("2022-10-31T05:25:18.122Z"),
"lastHeartbeatRecv" : ISODate("2022-10-31T05:25:18.120Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncSourceHost" : "mongo-rs-hid-0.mongo-rs-hid-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 0,
"infoMessage" : "",
"configVersion" : 5,
"configTerm" : 1
},
{
"_id" : 2,
"name" : "mongo-rs-hid-2.mongo-rs-hid-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 1237,
"optime" : {
"ts" : Timestamp(1667193912, 1),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1667193912, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2022-10-31T05:25:12Z"),
"optimeDurableDate" : ISODate("2022-10-31T05:25:12Z"),
"lastHeartbeat" : ISODate("2022-10-31T05:25:18.118Z"),
"lastHeartbeatRecv" : ISODate("2022-10-31T05:25:18.119Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncSourceHost" : "mongo-rs-hid-0.mongo-rs-hid-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 0,
"infoMessage" : "",
"configVersion" : 5,
"configTerm" : 1
},
{
"_id" : 3,
"name" : "mongo-rs-hid-hidden-0.mongo-rs-hid-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 1213,
"optime" : {
"ts" : Timestamp(1667193912, 1),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1667193912, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2022-10-31T05:25:12Z"),
"optimeDurableDate" : ISODate("2022-10-31T05:25:12Z"),
"lastHeartbeat" : ISODate("2022-10-31T05:25:18.118Z"),
"lastHeartbeatRecv" : ISODate("2022-10-31T05:25:18.119Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncSourceHost" : "mongo-rs-hid-2.mongo-rs-hid-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 2,
"infoMessage" : "",
"configVersion" : 5,
"configTerm" : 1
},
{
"_id" : 4,
"name" : "mongo-rs-hid-hidden-1.mongo-rs-hid-pods.demo.svc.cluster.local:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 1187,
"optime" : {
"ts" : Timestamp(1667193912, 1),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1667193912, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2022-10-31T05:25:12Z"),
"optimeDurableDate" : ISODate("2022-10-31T05:25:12Z"),
"lastHeartbeat" : ISODate("2022-10-31T05:25:18.119Z"),
"lastHeartbeatRecv" : ISODate("2022-10-31T05:25:18.008Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncSourceHost" : "mongo-rs-hid-2.mongo-rs-hid-pods.demo.svc.cluster.local:27017",
"syncSourceId" : 2,
"infoMessage" : "",
"configVersion" : 5,
"configTerm" : 1
}
],
"ok" : 1,
"$clusterTime" : {
"clusterTime" : Timestamp(1667193912, 1),
"signature" : {
"hash" : BinData(0,"EPi/BjSrT3iN3lqSAFcCynAqlP0="),
"keyId" : NumberLong("7160537873521836037")
}
},
"operationTime" : Timestamp(1667193912, 1)
}
Here, Hidden-node’s statestr is showing SECONDARY. If you want to see if they have been really added as hidden or not, you need to run rs.conf() command, look at the hidden: true specifications.
replicaset:PRIMARY> rs.conf()
{
"_id" : "replicaset",
"version" : 5,
"term" : 1,
"protocolVersion" : NumberLong(1),
"writeConcernMajorityJournalDefault" : false,
"members" : [
{
"_id" : 0,
"host" : "mongo-rs-hid-0.mongo-rs-hid-pods.demo.svc.cluster.local:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
},
{
"_id" : 1,
"host" : "mongo-rs-hid-1.mongo-rs-hid-pods.demo.svc.cluster.local:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
},
{
"_id" : 2,
"host" : "mongo-rs-hid-2.mongo-rs-hid-pods.demo.svc.cluster.local:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
},
{
"_id" : 3,
"host" : "mongo-rs-hid-hidden-0.mongo-rs-hid-pods.demo.svc.cluster.local:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : true,
"priority" : 0,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
},
{
"_id" : 4,
"host" : "mongo-rs-hid-hidden-1.mongo-rs-hid-pods.demo.svc.cluster.local:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : true,
"priority" : 0,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
}
],
"settings" : {
"chainingAllowed" : true,
"heartbeatIntervalMillis" : 2000,
"heartbeatTimeoutSecs" : 10,
"electionTimeoutMillis" : 10000,
"catchUpTimeoutMillis" : -1,
"catchUpTakeoverDelayMillis" : 30000,
"getLastErrorModes" : {
},
"getLastErrorDefaults" : {
"w" : 1,
"wtimeout" : 0
},
"replicaSetId" : ObjectId("635f574270b72a363804832f")
replicaset:PRIMARY> rs.isMaster().primary
mongo-rs-hid-0.mongo-rs-hid-pods.demo.svc.cluster.local:27017
replicaset:PRIMARY> show dbs
admin 0.000GB
config 0.000GB
kubedb-system 0.000GB
local 0.000GB
replicaset:PRIMARY> use admin
switched to db admin
replicaset:PRIMARY> show users
{
"_id" : "admin.root",
"userId" : UUID("5473e955-a97d-4c8f-a4fe-a82cbe7183f4"),
"user" : "root",
"db" : "admin",
"roles" : [
{
"role" : "root",
"db" : "admin"
}
],
"mechanisms" : [
"SCRAM-SHA-1",
"SCRAM-SHA-256"
]
}
replicaset:PRIMARY> use mydb
switched to db mydb
replicaset:PRIMARY> db.songs.insert({"pink floyd": "shine on you crazy diamond"})
WriteResult({ "nInserted" : 1 })
replicaset:PRIMARY> db.songs.find().pretty()
{
"_id" : ObjectId("635f5df01804db954f81276e"),
"pink floyd" : "shine on you crazy diamond"
}
replicaset:PRIMARY> exit
bye
Now, check the redundancy and data availability in secondary members.
We will exec in mongo-rs-hid-hidden-0(which is a hidden node right now) to check the data availability.
$ kubectl exec -it mongo-rs-hid-hidden-0 -n demo bash
bash-4.4$ mongo admin -u root -p 'OX4yb!IFm;~yAHkD'
Percona Server for MongoDB server version: v7.0.4-11
connecting to: mongodb://127.0.0.1:27017/admin
MongoDB server version: 7.0.4
Welcome to the MongoDB shell.
replicaset:SECONDARY> rs.slaveOk()
WARNING: slaveOk() is deprecated and may be removed in the next major release. Please use secondaryOk() instead.
replicaset:SECONDARY> show dbs
admin 0.000GB
config 0.000GB
kubedb-system 0.000GB
local 0.000GB
mydb 0.000GB
replicaset:SECONDARY> use admin
switched to db admin
replicaset:SECONDARY> show users
{
"_id" : "admin.root",
"userId" : UUID("5473e955-a97d-4c8f-a4fe-a82cbe7183f4"),
"user" : "root",
"db" : "admin",
"roles" : [
{
"role" : "root",
"db" : "admin"
}
],
"mechanisms" : [
"SCRAM-SHA-1",
"SCRAM-SHA-256"
]
}
replicaset:SECONDARY> use mydb
switched to db mydb
replicaset:SECONDARY> db.songs.find().pretty()
{
"_id" : ObjectId("635f5df01804db954f81276e"),
"pink floyd" : "shine on you crazy diamond"
}
rs0:SECONDARY> exit
bye
Automatic Failover
To test automatic failover, we will force the primary member to restart. As the primary member (pod) becomes unavailable, the rest of the members will elect a primary member by election.
$ kubectl get pods -n demo
NAME READY STATUS RESTARTS AGE
mongo-rs-hid-0 2/2 Running 0 34m
mongo-rs-hid-1 2/2 Running 0 33m
mongo-rs-hid-2 2/2 Running 0 33m
mongo-rs-hid-hidden-0 1/1 Running 0 33m
mongo-rs-hid-hidden-1 1/1 Running 0 32m
$ kubectl delete pod -n demo mongo-rs-hid-0
pod "mongo-rs-hid-0" deleted
$ kubectl get pods -n demo
NAME READY STATUS RESTARTS AGE
mongo-rs-hid-0 2/2 Terminating 0 34m
mongo-rs-hid-1 2/2 Running 0 33m
mongo-rs-hid-2 2/2 Running 0 33m
mongo-rs-hid-hidden-0 1/1 Running 0 33m
mongo-rs-hid-hidden-1 1/1 Running 0 32m
Now verify the automatic failover, Let’s exec in mongo-rs-hid-0 pod,
$ kubectl exec -it mongo-rs-hid-0 -n demo bash
bash-4.4:/$ mongo admin -u root -p 'OX4yb!IFm;~yAHkD'
Percona Server for MongoDB server version: v7.0.4-11
connecting to: mongodb://127.0.0.1:27017/admin
MongoDB server version: 7.0.4
Welcome to the MongoDB shell.
replicaset:SECONDARY> rs.isMaster().primary
mongo-rs-hid-1.mongo-rs-hid-pods.demo.svc.cluster.local:27017
# Also verify, data persistency
replicaset:SECONDARY> rs.slaveOk()
replicaset:SECONDARY> > show dbs
admin 0.000GB
config 0.000GB
kubedb-system 0.000GB
local 0.000GB
mydb 0.000GB
replicaset:SECONDARY> use mydb
switched to db mydb
replicaset:SECONDARY> db.songs.find().pretty()
{
"_id" : ObjectId("635f5df01804db954f81276e"),
"pink floyd" : "shine on you crazy diamond"
}
We could terminate the hidden-nodes also in a similar fashion, & check the automatic failover.
Cleaning up
To cleanup the Kubernetes resources created by this tutorial, run:
kubectl delete -n demo mg/mongo-rs-hid
kubectl delete ns demo
Next Steps
- Deploy MongoDB shard with Hidden-node.
- Backup and Restore process of MongoDB databases using Stash.
- Initialize MongoDB with Script.
- Monitor your MongoDB database with KubeDB using out-of-the-box Prometheus operator.
- Monitor your MongoDB database with KubeDB using out-of-the-box builtin-Prometheus.
- Use private Docker registry to deploy MongoDB with KubeDB.
- Detail concepts of MongoDB object.
- Detail concepts of MongoDBVersion object.
- Want to hack on KubeDB? Check our contribution guidelines.