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MongoDB Sharding
This tutorial will show you how to use KubeDB to run a sharded MongoDB cluster.
Before You Begin
Before proceeding:
Read mongodb sharding concept to learn about MongoDB Sharding clustering.
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 Sharded MongoDB Cluster
To deploy a MongoDB Sharding, user have to specify spec.shardTopology option in Mongodb CRD.
The following is an example of a Mongodb object which creates MongoDB Sharding of three members.
apiVersion: kubedb.com/v1alpha2
kind: MongoDB
metadata:
name: mongo-sh
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
$ kubectl create -f https://github.com/kubedb/docs/raw/v2022.12.24-rc.1/docs/examples/mongodb/clustering/mongo-sharding.yaml
mongodb.kubedb.com/mongo-sh created
Here,
spec.shardTopologyrepresents the topology configuration for sharding.shardrepresents configuration for Shard component of mongodb.shardsrepresents number of shards for a mongodb deployment. Each shard is deployed as a replicaset.replicasrepresents number of replicas of each shard replicaset.prefixrepresents the prefix of each shard node.configSecretis an optional field to provide custom configuration file for shards (i.e mongod.cnf). If specified, this file will be used as configuration file otherwise a default configuration file will be used.podTemplateis an optional configuration for pods.storageto specify pvc spec for each node of sharding. You can specify any StorageClass available in your cluster with appropriate resource requests.
configServerrepresents configuration for ConfigServer component of mongodb.replicasrepresents number of replicas for configServer replicaset. Here, configServer is deployed as a replicaset of mongodb.prefixrepresents the prefix of configServer nodes.configSecretis an optional field to provide custom configuration file for configSource (i.e mongod.cnf). If specified, this file will be used as configuration file otherwise a default configuration file will be used.podTemplateis an optional configuration for pods.storageto specify pvc spec for each node of configServer. You can specify any StorageClass available in your cluster with appropriate resource requests.
mongosrepresents configuration for Mongos component of mongodb.Mongosinstances run as stateless components (deployment).replicasrepresents number of replicas ofMongosinstance. Here, Mongos is not deployed as replicaset.prefixrepresents the prefix of mongos nodes.configSecretis an optional field to provide custom configuration file for mongos (i.e mongod.cnf). If specified, this file will be used as configuration file otherwise a default configuration file will be used.podTemplateis an optional configuration for pods.
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.
KubeDB operator watches for MongoDB objects using Kubernetes api. When a MongoDB object is created, KubeDB operator will create some new StatefulSets : 1 for mongos, 1 for configServer & 1 for each of the shards. It creates a primary Service with the matching MongoDB object name. KubeDB operator will also create governing services for StatefulSets with the name <mongodb-name>-<node-type>-pods.
MongoDB mongo-sh state,
$ kubectl get mg -n demo
NAME VERSION STATUS AGE
mongo-sh 4.2.3 Ready 9m41s
All the types of nodes Shard, ConfigServer & Mongos are deployed as statefulset.
$ kubectl get statefulset -n demo
NAME READY AGE
mongo-sh-configsvr 3/3 11m
mongo-sh-mongos 3/3 8m41s
mongo-sh-shard0 3/3 10m
mongo-sh-shard1 3/3 8m59s
All PVCs and PVs for MongoDB mongo-sh,
$ kubectl get pvc -n demo
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
datadir-mongo-sh-configsvr-0 Bound pvc-1db4185e-6a5f-11e9-a871-080027a851ba 1Gi RWO standard 16m
datadir-mongo-sh-configsvr-1 Bound pvc-330cc6ee-6a5f-11e9-a871-080027a851ba 1Gi RWO standard 16m
datadir-mongo-sh-configsvr-2 Bound pvc-3db2d3f5-6a5f-11e9-a871-080027a851ba 1Gi RWO standard 15m
datadir-mongo-sh-shard0-0 Bound pvc-49b7cc3b-6a5f-11e9-a871-080027a851ba 1Gi RWO standard 15m
datadir-mongo-sh-shard0-1 Bound pvc-5b781770-6a5f-11e9-a871-080027a851ba 1Gi RWO standard 15m
datadir-mongo-sh-shard0-2 Bound pvc-6ba3263e-6a5f-11e9-a871-080027a851ba 1Gi RWO standard 14m
datadir-mongo-sh-shard1-0 Bound pvc-75feb227-6a5f-11e9-a871-080027a851ba 1Gi RWO standard 14m
datadir-mongo-sh-shard1-1 Bound pvc-89bb7bb3-6a5f-11e9-a871-080027a851ba 1Gi RWO standard 13m
datadir-mongo-sh-shard1-2 Bound pvc-98c96ae4-6a5f-11e9-a871-080027a851ba 1Gi RWO standard 13m
$ kubectl get pv -n demo
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pvc-1db4185e-6a5f-11e9-a871-080027a851ba 1Gi RWO Delete Bound demo/datadir-mongo-sh-configsvr-0 standard 17m
pvc-330cc6ee-6a5f-11e9-a871-080027a851ba 1Gi RWO Delete Bound demo/datadir-mongo-sh-configsvr-1 standard 16m
pvc-3db2d3f5-6a5f-11e9-a871-080027a851ba 1Gi RWO Delete Bound demo/datadir-mongo-sh-configsvr-2 standard 16m
pvc-49b7cc3b-6a5f-11e9-a871-080027a851ba 1Gi RWO Delete Bound demo/datadir-mongo-sh-shard0-0 standard 16m
pvc-5b781770-6a5f-11e9-a871-080027a851ba 1Gi RWO Delete Bound demo/datadir-mongo-sh-shard0-1 standard 15m
pvc-6ba3263e-6a5f-11e9-a871-080027a851ba 1Gi RWO Delete Bound demo/datadir-mongo-sh-shard0-2 standard 15m
pvc-75feb227-6a5f-11e9-a871-080027a851ba 1Gi RWO Delete Bound demo/datadir-mongo-sh-shard1-0 standard 14m
pvc-89bb7bb3-6a5f-11e9-a871-080027a851ba 1Gi RWO Delete Bound demo/datadir-mongo-sh-shard1-1 standard 14m
pvc-98c96ae4-6a5f-11e9-a871-080027a851ba 1Gi RWO Delete Bound demo/datadir-mongo-sh-shard1-2 standard 13m
Services created for MongoDB mongo-sh
$ kubectl get svc -n demo
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
mongo-sh ClusterIP 10.108.188.201 <none> 27017/TCP 18m
mongo-sh-configsvr-pods ClusterIP None <none> 27017/TCP 18m
mongo-sh-mongos-pods ClusterIP None <none> 27017/TCP 18m
mongo-sh-shard0-pods ClusterIP None <none> 27017/TCP 18m
mongo-sh-shard1-pods ClusterIP None <none> 27017/TCP 18m
KubeDB operator sets the status.phase to Ready once the database is successfully created. It has also defaulted some field of crd object. Run the following command to see the modified MongoDB object:
$ kubectl get mg -n demo mongo-sh -o yaml
apiVersion: kubedb.com/v1alpha2
kind: MongoDB
metadata:
annotations:
kubectl.kubernetes.io/last-applied-configuration: |
{"apiVersion":"kubedb.com/v1alpha2","kind":"MongoDB","metadata":{"annotations":{},"name":"mongo-sh","namespace":"demo"},"spec":{"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"}}},"version":"4.2.3"}}
creationTimestamp: "2021-02-10T12:57:03Z"
finalizers:
- kubedb.com
generation: 3
managedFields:
- apiVersion: kubedb.com/v1alpha2
fieldsType: FieldsV1
fieldsV1:
f:metadata:
f:annotations:
.: {}
f:kubectl.kubernetes.io/last-applied-configuration: {}
f:spec:
.: {}
f:shardTopology:
.: {}
f:configServer:
.: {}
f:replicas: {}
f:storage:
.: {}
f:resources:
.: {}
f:requests:
.: {}
f:storage: {}
f:storageClassName: {}
f:mongos:
.: {}
f:replicas: {}
f:shard:
.: {}
f:replicas: {}
f:shards: {}
f:storage:
.: {}
f:resources:
.: {}
f:requests:
.: {}
f:storage: {}
f:storageClassName: {}
f:version: {}
manager: kubectl-client-side-apply
operation: Update
time: "2021-02-10T12:57:03Z"
- apiVersion: kubedb.com/v1alpha2
fieldsType: FieldsV1
fieldsV1:
f:metadata:
f:finalizers: {}
f:spec:
f:authSecret:
.: {}
f:name: {}
f:keyFileSecret:
.: {}
f:name: {}
f:status:
.: {}
f:conditions: {}
f:observedGeneration: {}
f:phase: {}
manager: mg-operator
operation: Update
time: "2021-02-10T12:57:03Z"
name: mongo-sh
namespace: demo
resourceVersion: "152268"
uid: 8522c8c1-344b-4824-9061-47031b88f1fa
spec:
authSecret:
name: mongo-sh-auth
clusterAuthMode: keyFile
keyFileSecret:
name: mongo-sh-key
shardTopology:
configServer:
podTemplate:
controller: {}
metadata: {}
spec:
affinity:
podAntiAffinity:
preferredDuringSchedulingIgnoredDuringExecution:
- podAffinityTerm:
labelSelector:
matchLabels:
app.kubernetes.io/instance: mongo-sh
app.kubernetes.io/managed-by: kubedb.com
app.kubernetes.io/name: mongodbs.kubedb.com
mongodb.kubedb.com/node.config: mongo-sh-configsvr
namespaces:
- demo
topologyKey: kubernetes.io/hostname
weight: 100
- podAffinityTerm:
labelSelector:
matchLabels:
app.kubernetes.io/instance: mongo-sh
app.kubernetes.io/managed-by: kubedb.com
app.kubernetes.io/name: mongodbs.kubedb.com
mongodb.kubedb.com/node.config: mongo-sh-configsvr
namespaces:
- demo
topologyKey: failure-domain.beta.kubernetes.io/zone
weight: 50
livenessProbe:
exec:
command:
- bash
- -c
- "set -x; if [[ $(mongo admin --host=localhost --username=$MONGO_INITDB_ROOT_USERNAME
--password=$MONGO_INITDB_ROOT_PASSWORD --authenticationDatabase=admin
--quiet --eval \"db.adminCommand('ping').ok\" ) -eq \"1\" ]]; then
\n exit 0\n fi\n exit 1"
failureThreshold: 3
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 5
readinessProbe:
exec:
command:
- bash
- -c
- "set -x; if [[ $(mongo admin --host=localhost --username=$MONGO_INITDB_ROOT_USERNAME
--password=$MONGO_INITDB_ROOT_PASSWORD --authenticationDatabase=admin
--quiet --eval \"db.adminCommand('ping').ok\" ) -eq \"1\" ]]; then
\n exit 0\n fi\n exit 1"
failureThreshold: 3
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 1
resources:
limits:
cpu: 500m
memory: 1Gi
requests:
cpu: 500m
memory: 1Gi
serviceAccountName: mongo-sh
replicas: 3
storage:
resources:
requests:
storage: 1Gi
storageClassName: standard
mongos:
podTemplate:
controller: {}
metadata: {}
spec:
affinity:
podAntiAffinity:
preferredDuringSchedulingIgnoredDuringExecution:
- podAffinityTerm:
labelSelector:
matchLabels:
app.kubernetes.io/instance: mongo-sh
app.kubernetes.io/managed-by: kubedb.com
app.kubernetes.io/name: mongodbs.kubedb.com
mongodb.kubedb.com/node.mongos: mongo-sh-mongos
namespaces:
- demo
topologyKey: kubernetes.io/hostname
weight: 100
- podAffinityTerm:
labelSelector:
matchLabels:
app.kubernetes.io/instance: mongo-sh
app.kubernetes.io/managed-by: kubedb.com
app.kubernetes.io/name: mongodbs.kubedb.com
mongodb.kubedb.com/node.mongos: mongo-sh-mongos
namespaces:
- demo
topologyKey: failure-domain.beta.kubernetes.io/zone
weight: 50
lifecycle:
preStop:
exec:
command:
- bash
- -c
- 'mongo admin --username=$MONGO_INITDB_ROOT_USERNAME --password=$MONGO_INITDB_ROOT_PASSWORD
--quiet --eval "db.adminCommand({ shutdown: 1 })" || true'
livenessProbe:
exec:
command:
- bash
- -c
- "set -x; if [[ $(mongo admin --host=localhost --username=$MONGO_INITDB_ROOT_USERNAME
--password=$MONGO_INITDB_ROOT_PASSWORD --authenticationDatabase=admin
--quiet --eval \"db.adminCommand('ping').ok\" ) -eq \"1\" ]]; then
\n exit 0\n fi\n exit 1"
failureThreshold: 3
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 5
readinessProbe:
exec:
command:
- bash
- -c
- "set -x; if [[ $(mongo admin --host=localhost --username=$MONGO_INITDB_ROOT_USERNAME
--password=$MONGO_INITDB_ROOT_PASSWORD --authenticationDatabase=admin
--quiet --eval \"db.adminCommand('ping').ok\" ) -eq \"1\" ]]; then
\n exit 0\n fi\n exit 1"
failureThreshold: 3
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 1
resources:
limits:
cpu: 500m
memory: 1Gi
requests:
cpu: 500m
memory: 1Gi
serviceAccountName: mongo-sh
replicas: 2
shard:
podTemplate:
controller: {}
metadata: {}
spec:
affinity:
podAntiAffinity:
preferredDuringSchedulingIgnoredDuringExecution:
- podAffinityTerm:
labelSelector:
matchLabels:
app.kubernetes.io/instance: mongo-sh
app.kubernetes.io/managed-by: kubedb.com
app.kubernetes.io/name: mongodbs.kubedb.com
mongodb.kubedb.com/node.shard: mongo-sh-shard${SHARD_INDEX}
namespaces:
- demo
topologyKey: kubernetes.io/hostname
weight: 100
- podAffinityTerm:
labelSelector:
matchLabels:
app.kubernetes.io/instance: mongo-sh
app.kubernetes.io/managed-by: kubedb.com
app.kubernetes.io/name: mongodbs.kubedb.com
mongodb.kubedb.com/node.shard: mongo-sh-shard${SHARD_INDEX}
namespaces:
- demo
topologyKey: failure-domain.beta.kubernetes.io/zone
weight: 50
livenessProbe:
exec:
command:
- bash
- -c
- "set -x; if [[ $(mongo admin --host=localhost --username=$MONGO_INITDB_ROOT_USERNAME
--password=$MONGO_INITDB_ROOT_PASSWORD --authenticationDatabase=admin
--quiet --eval \"db.adminCommand('ping').ok\" ) -eq \"1\" ]]; then
\n exit 0\n fi\n exit 1"
failureThreshold: 3
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 5
readinessProbe:
exec:
command:
- bash
- -c
- "set -x; if [[ $(mongo admin --host=localhost --username=$MONGO_INITDB_ROOT_USERNAME
--password=$MONGO_INITDB_ROOT_PASSWORD --authenticationDatabase=admin
--quiet --eval \"db.adminCommand('ping').ok\" ) -eq \"1\" ]]; then
\n exit 0\n fi\n exit 1"
failureThreshold: 3
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 1
resources:
limits:
cpu: 500m
memory: 1Gi
requests:
cpu: 500m
memory: 1Gi
serviceAccountName: mongo-sh
replicas: 3
shards: 2
storage:
resources:
requests:
storage: 1Gi
storageClassName: standard
sslMode: disabled
storageEngine: wiredTiger
storageType: Durable
terminationPolicy: Delete
version: 4.2.3
status:
conditions:
- lastTransitionTime: "2021-02-10T12:57:03Z"
message: 'The KubeDB operator has started the provisioning of MongoDB: demo/mongo-sh'
reason: DatabaseProvisioningStartedSuccessfully
status: "True"
type: ProvisioningStarted
- lastTransitionTime: "2021-02-10T13:09:44Z"
message: All desired replicas are ready.
reason: AllReplicasReady
status: "True"
type: ReplicaReady
- lastTransitionTime: "2021-02-10T12:59:33Z"
message: 'The MongoDB: demo/mongo-sh is accepting client requests.'
observedGeneration: 3
reason: DatabaseAcceptingConnectionRequest
status: "True"
type: AcceptingConnection
- lastTransitionTime: "2021-02-10T12:59:33Z"
message: 'The MongoDB: demo/mongo-sh is ready.'
observedGeneration: 3
reason: ReadinessCheckSucceeded
status: "True"
type: Ready
- lastTransitionTime: "2021-02-10T12:59:51Z"
message: 'The MongoDB: demo/mongo-sh 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-sh-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.
Connection Information
Hostname/address: you can use any of these
- Service:
mongo-sh.demo - Pod IP: (
$ kubectl get po -n demo -l mongodb.kubedb.com/node.mongos=mongo-sh-mongos -o yaml | grep podIP)
- Service:
Port:
27017Username: Run following command to get username,
$ kubectl get secrets -n demo mongo-sh-auth -o jsonpath='{.data.\username}' | base64 -d rootPassword: Run the following command to get password,
$ kubectl get secrets -n demo mongo-sh-auth -o jsonpath='{.data.\password}' | base64 -d 7QiqLcuSCmZ8PU5a
Now, you can connect to this database through mongo-shell.
Sharded Data
In this tutorial, we will insert sharded and unsharded document, and we will see if the data actually sharded across cluster or not.
$ kubectl get po -n demo -l mongodb.kubedb.com/node.mongos=mongo-sh-mongos
NAME READY STATUS RESTARTS AGE
mongo-sh-mongos-0 1/1 Running 0 49m
mongo-sh-mongos-1 1/1 Running 0 49m
$ kubectl exec -it mongo-sh-mongos-0 -n demo bash
mongodb@mongo-sh-mongos-0:/$ mongo admin -u root -p 7QiqLcuSCmZ8PU5a
MongoDB shell version v4.2.3
connecting to: mongodb://127.0.0.1:27017/admin?gssapiServiceName=mongodb
Implicit session: session { "id" : UUID("8b7abf57-09e4-4e30-b4a0-a37ebf065e8f") }
MongoDB server version: 4.2.3
Welcome to the MongoDB shell.
For interactive help, type "help".
For more comprehensive documentation, see
http://docs.mongodb.org/
Questions? Try the support group
http://groups.google.com/group/mongodb-user
mongos>
To detect if the MongoDB instance that your client is connected to is mongos, use the isMaster command. When a client connects to a mongos, isMaster returns a document with a msg field that holds the string isdbgrid.
mongos> rs.isMaster()
{
"ismaster" : true,
"msg" : "isdbgrid",
"maxBsonObjectSize" : 16777216,
"maxMessageSizeBytes" : 48000000,
"maxWriteBatchSize" : 100000,
"localTime" : ISODate("2021-02-10T13:37:24.140Z"),
"logicalSessionTimeoutMinutes" : 30,
"connectionId" : 803,
"maxWireVersion" : 8,
"minWireVersion" : 0,
"ok" : 1,
"operationTime" : Timestamp(1612964237, 2),
"$clusterTime" : {
"clusterTime" : Timestamp(1612964237, 2),
"signature" : {
"hash" : BinData(0,"5ugX3jIC+sVDtYjxGWP5SCI7QSE="),
"keyId" : NumberLong("6927618399740624913")
}
}
}
mongo-sh Shard status,
mongos> sh.status()
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId("6023d83b8df2b687ecfade84")
}
shards:
{ "_id" : "shard0", "host" : "shard0/mongo-sh-shard0-0.mongo-sh-shard0-pods.demo.svc.cluster.local:27017,mongo-sh-shard0-1.mongo-sh-shard0-pods.demo.svc.cluster.local:27017,mongo-sh-shard0-2.mongo-sh-shard0-pods.demo.svc.cluster.local:27017", "state" : 1 }
{ "_id" : "shard1", "host" : "shard1/mongo-sh-shard1-0.mongo-sh-shard1-pods.demo.svc.cluster.local:27017,mongo-sh-shard1-1.mongo-sh-shard1-pods.demo.svc.cluster.local:27017,mongo-sh-shard1-2.mongo-sh-shard1-pods.demo.svc.cluster.local:27017", "state" : 1 }
active mongoses:
"4.2.3" : 2
autosplit:
Currently enabled: yes
balancer:
Currently enabled: yes
Currently running: no
Failed balancer rounds in last 5 attempts: 0
Migration Results for the last 24 hours:
No recent migrations
databases:
{ "_id" : "config", "primary" : "config", "partitioned" : true }
config.system.sessions
shard key: { "_id" : 1 }
unique: false
balancing: true
chunks:
shard0 1
{ "_id" : { "$minKey" : 1 } } -->> { "_id" : { "$maxKey" : 1 } } on : shard0 Timestamp(1, 0)
Shard collection test.testcoll and insert document. See sh.shardCollection(namespace, key, unique, options) for details about shardCollection command.
mongos> sh.enableSharding("test");
{
"ok" : 1,
"operationTime" : Timestamp(1612964293, 5),
"$clusterTime" : {
"clusterTime" : Timestamp(1612964293, 5),
"signature" : {
"hash" : BinData(0,"DJbXhWUbiTQCWvlWgTTW/vlH3LE="),
"keyId" : NumberLong("6927618399740624913")
}
}
}
mongos> sh.shardCollection("test.testcoll", {"myfield": 1});
{
"collectionsharded" : "test.testcoll",
"collectionUUID" : UUID("f2617eb1-8f61-47dd-af58-73f5fe4ea2c0"),
"ok" : 1,
"operationTime" : Timestamp(1612964314, 14),
"$clusterTime" : {
"clusterTime" : Timestamp(1612964314, 14),
"signature" : {
"hash" : BinData(0,"CZzOATrFeADxMkGTWbX85Olkc2Q="),
"keyId" : NumberLong("6927618399740624913")
}
}
}
mongos> use test;
switched to db test
mongos> db.testcoll.insert({"myfield": "a", "otherfield": "b"});
WriteResult({ "nInserted" : 1 })
mongos> db.testcoll.insert({"myfield": "c", "otherfield": "d", "kube" : "db" });
WriteResult({ "nInserted" : 1 })
mongos> db.testcoll.find();
{ "_id" : ObjectId("5cc6d6f656a9ddd30be2c12a"), "myfield" : "a", "otherfield" : "b" }
{ "_id" : ObjectId("5cc6d71e56a9ddd30be2c12b"), "myfield" : "c", "otherfield" : "d", "kube" : "db" }
Run sh.status() to see whether the test database has sharding enabled, and the primary shard for the test database.
The Sharded Collection section sh.status.databases.<collection> provides information on the sharding details for sharded collection(s) (E.g. test.testcoll). For each sharded collection, the section displays the shard key, the number of chunks per shard(s), the distribution of documents across chunks, and the tag information, if any, for shard key range(s).
mongos> sh.status();
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId("6023d83b8df2b687ecfade84")
}
shards:
{ "_id" : "shard0", "host" : "shard0/mongo-sh-shard0-0.mongo-sh-shard0-pods.demo.svc.cluster.local:27017,mongo-sh-shard0-1.mongo-sh-shard0-pods.demo.svc.cluster.local:27017,mongo-sh-shard0-2.mongo-sh-shard0-pods.demo.svc.cluster.local:27017", "state" : 1 }
{ "_id" : "shard1", "host" : "shard1/mongo-sh-shard1-0.mongo-sh-shard1-pods.demo.svc.cluster.local:27017,mongo-sh-shard1-1.mongo-sh-shard1-pods.demo.svc.cluster.local:27017,mongo-sh-shard1-2.mongo-sh-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 }
config.system.sessions
shard key: { "_id" : 1 }
unique: false
balancing: true
chunks:
shard0 1
{ "_id" : { "$minKey" : 1 } } -->> { "_id" : { "$maxKey" : 1 } } on : shard0 Timestamp(1, 0)
{ "_id" : "test", "primary" : "shard1", "partitioned" : true, "version" : { "uuid" : UUID("2a39d8c7-c731-46af-84c3-bf04ba10ac82"), "lastMod" : 1 } }
test.testcoll
shard key: { "myfield" : 1 }
unique: false
balancing: true
chunks:
shard1 1
{ "myfield" : { "$minKey" : 1 } } -->> { "myfield" : { "$maxKey" : 1 } } on : shard1 Timestamp(1, 0)
Now create another database where partiotioned is not applied and see how the data is stored.
mongos> use demo
switched to db demo
mongos> db.testcoll2.insert({"myfield": "ccc", "otherfield": "d", "kube" : "db" });
WriteResult({ "nInserted" : 1 })
mongos> db.testcoll2.insert({"myfield": "aaa", "otherfield": "d", "kube" : "db" });
WriteResult({ "nInserted" : 1 })
mongos> db.testcoll2.find()
{ "_id" : ObjectId("5cc6dc831b6d9b3cddc947ec"), "myfield" : "ccc", "otherfield" : "d", "kube" : "db" }
{ "_id" : ObjectId("5cc6dce71b6d9b3cddc947ed"), "myfield" : "aaa", "otherfield" : "d", "kube" : "db" }
Now, eventually sh.status()
mongos> sh.status()
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId("6023d83b8df2b687ecfade84")
}
shards:
{ "_id" : "shard0", "host" : "shard0/mongo-sh-shard0-0.mongo-sh-shard0-pods.demo.svc.cluster.local:27017,mongo-sh-shard0-1.mongo-sh-shard0-pods.demo.svc.cluster.local:27017,mongo-sh-shard0-2.mongo-sh-shard0-pods.demo.svc.cluster.local:27017", "state" : 1 }
{ "_id" : "shard1", "host" : "shard1/mongo-sh-shard1-0.mongo-sh-shard1-pods.demo.svc.cluster.local:27017,mongo-sh-shard1-1.mongo-sh-shard1-pods.demo.svc.cluster.local:27017,mongo-sh-shard1-2.mongo-sh-shard1-pods.demo.svc.cluster.local:27017", "state" : 1 }
active mongoses:
"4.2.3" : 2
autosplit:
Currently enabled: yes
balancer:
Currently enabled: yes
Currently running: no
Failed balancer rounds in last 5 attempts: 0
Migration Results for the last 24 hours:
No recent migrations
databases:
{ "_id" : "config", "primary" : "config", "partitioned" : true }
config.system.sessions
shard key: { "_id" : 1 }
unique: false
balancing: true
chunks:
shard0 1
{ "_id" : { "$minKey" : 1 } } -->> { "_id" : { "$maxKey" : 1 } } on : shard0 Timestamp(1, 0)
{ "_id" : "demo", "primary" : "shard1", "partitioned" : false, "version" : { "uuid" : UUID("93d077e0-2da0-4b68-a4d4-d23394b22ab2"), "lastMod" : 1 } }
{ "_id" : "test", "primary" : "shard1", "partitioned" : true, "version" : { "uuid" : UUID("2a39d8c7-c731-46af-84c3-bf04ba10ac82"), "lastMod" : 1 } }
test.testcoll
shard key: { "myfield" : 1 }
unique: false
balancing: true
chunks:
shard1 1
{ "myfield" : { "$minKey" : 1 } } -->> { "myfield" : { "$maxKey" : 1 } } on : shard1 Timestamp(1, 0)
Here, demo database is not partitioned and all collections under demo database are stored in it’s primary shard, which is shard1.
Halt Database
When TerminationPolicy is set to halt, and you delete the mongodb object, the KubeDB operator will delete the StatefulSet and its pods but leaves the PVCs, secrets and database backup (snapshots) intact. Learn details of all TerminationPolicy here.
You can also keep the mongodb object and halt the database to resume it again later. If you halt the database, the kubedb will delete the statefulsets and services but will keep the mongodb object, pvcs, secrets and backup (snapshots).
To halt the database, first you have to set the terminationPolicy to Halt in existing database. You can use the below command to set the terminationPolicy to Halt, if it is not already set.
$ kubectl patch -n demo mg/mongo-sh -p '{"spec":{"terminationPolicy":"Halt"}}' --type="merge"
mongodb.kubedb.com/mongo-sh patched
Then, you have to set the spec.halted as true to set the database in a Halted state. You can use the below command.
$ kubectl patch -n demo mg/mongo-sh -p '{"spec":{"halted":true}}' --type="merge"
mongodb.kubedb.com/mongo-sh patched
After that, kubedb will delete the statefulsets and services and you can see the database Phase as Halted.
Now, you can run the following command to get all mongodb resources in demo namespaces,
$ kubectl get mg,sts,svc,secret,pvc -n demo
NAME VERSION STATUS AGE
mongodb.kubedb.com/mongo-sh 4.2.3 Halted 74m
NAME TYPE DATA AGE
secret/default-token-x2zcl kubernetes.io/service-account-token 3 32h
secret/mongo-sh-auth Opaque 2 75m
secret/mongo-sh-key Opaque 1 75m
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
persistentvolumeclaim/datadir-mongo-sh-configsvr-0 Bound pvc-9d1b3c01-fdce-45ab-b6f6-fc7bf9462e89 1Gi RWO standard 74m
persistentvolumeclaim/datadir-mongo-sh-configsvr-1 Bound pvc-8e14fcea-ec15-4614-9ec5-21fdf3eb477c 1Gi RWO standard 74m
persistentvolumeclaim/datadir-mongo-sh-configsvr-2 Bound pvc-b65665ce-f35b-4c4f-a7ac-410ad2dfa82d 1Gi RWO standard 73m
persistentvolumeclaim/datadir-mongo-sh-shard0-0 Bound pvc-8fbfdd01-1ed1-4e3b-9a2a-0aa75911cbf0 1Gi RWO standard 74m
persistentvolumeclaim/datadir-mongo-sh-shard0-1 Bound pvc-71d2b22b-2168-46d3-927c-d3ac92f22ebb 1Gi RWO standard 74m
persistentvolumeclaim/datadir-mongo-sh-shard0-2 Bound pvc-82f83359-6e31-43e4-88b3-2555cb442ca0 1Gi RWO standard 73m
persistentvolumeclaim/datadir-mongo-sh-shard1-0 Bound pvc-07ef7cd3-99b2-47de-b1bb-ef6c5606d92e 1Gi RWO standard 74m
persistentvolumeclaim/datadir-mongo-sh-shard1-1 Bound pvc-ffa4b9a7-2492-4f18-be90-7950004e9efd 1Gi RWO standard 74m
persistentvolumeclaim/datadir-mongo-sh-shard1-2 Bound pvc-4e75b90e-dac5-4431-a50e-2bc8dfcf481b 1Gi RWO standard 73m
From the above output, you can see that MongoDB object, PVCs, Secret are still there.
Resume Halted Database
Now, to resume the database, i.e. to get the same database setup back again, you have to set the the spec.halted as false. You can use the below command.
$ kubectl patch -n demo mg/mongo-sh -p '{"spec":{"halted":false}}' --type="merge"
mongodb.kubedb.com/mongo-sh patched
When the database is resumed successfully, you can see the database Status is set to Ready.
$ kubectl get mg -n demo
NAME VERSION STATUS AGE
mongo-sh 4.2.3 Ready 6m27s
Now, If you again exec into pod and look for previous data, you will see that, all the data persists.
$ kubectl get po -n demo -l mongodb.kubedb.com/node.mongos=mongo-sh-mongos
NAME READY STATUS RESTARTS AGE
mongo-sh-mongos-0 1/1 Running 0 3m52s
mongo-sh-mongos-1 1/1 Running 0 3m52s
$ kubectl exec -it mongo-sh-mongos-0 -n demo bash
mongodb@mongo-sh-mongos-0:/$ mongo admin -u root -p 7QiqLcuSCmZ8PU5a
mongos> use test;
switched to db test
mongos> db.testcoll.find();
{ "_id" : ObjectId("5cc6d6f656a9ddd30be2c12a"), "myfield" : "a", "otherfield" : "b" }
{ "_id" : ObjectId("5cc6d71e56a9ddd30be2c12b"), "myfield" : "c", "otherfield" : "d", "kube" : "db" }
mongos> sh.status()
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId("6023d83b8df2b687ecfade84")
}
shards:
{ "_id" : "shard0", "host" : "shard0/mongo-sh-shard0-0.mongo-sh-shard0-pods.demo.svc.cluster.local:27017,mongo-sh-shard0-1.mongo-sh-shard0-pods.demo.svc.cluster.local:27017,mongo-sh-shard0-2.mongo-sh-shard0-pods.demo.svc.cluster.local:27017", "state" : 1 }
{ "_id" : "shard1", "host" : "shard1/mongo-sh-shard1-0.mongo-sh-shard1-pods.demo.svc.cluster.local:27017,mongo-sh-shard1-1.mongo-sh-shard1-pods.demo.svc.cluster.local:27017,mongo-sh-shard1-2.mongo-sh-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: 1
Last reported error: Could not find host matching read preference { mode: "primary" } for set shard0
Time of Reported error: Wed Feb 10 2021 14:16:04 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)
{ "_id" : "demo", "primary" : "shard1", "partitioned" : false, "version" : { "uuid" : UUID("93d077e0-2da0-4b68-a4d4-d23394b22ab2"), "lastMod" : 1 } }
{ "_id" : "test", "primary" : "shard1", "partitioned" : true, "version" : { "uuid" : UUID("2a39d8c7-c731-46af-84c3-bf04ba10ac82"), "lastMod" : 1 } }
test.testcoll
shard key: { "myfield" : 1 }
unique: false
balancing: true
chunks:
shard1 1
{ "myfield" : { "$minKey" : 1 } } -->> { "myfield" : { "$maxKey" : 1 } } on : shard1 Timestamp(1, 0)
Cleaning up
To cleanup the Kubernetes resources created by this tutorial, run:
kubectl patch -n demo mg/mongo-sh -p '{"spec":{"terminationPolicy":"WipeOut"}}' --type="merge"
kubectl delete -n demo mg/mongo-sh
kubectl delete ns demo
Next Steps
- 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.