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MongoDB + Kanister sidecar Helm Chart

Prerequisites Details

  • Kubernetes 1.8+ with Beta APIs enabled.
  • PV support on the underlying infrastructure.
  • Kanister version 0.15.0 with CRD installed

StatefulSet Details

StatefulSet Caveats

Chart Details

This chart implements a dynamically scalable MongoDB replica set using Kubernetes StatefulSets and Init Containers.

Installing the Chart

For basic installation, you can install using a the provided Helm chart that will install an instance of a MongoDB ReplicaSet (a StatefulSet with a persistent volumes) as well as a Kanister blueprint to be used with it.

Prior to install you will need to have the Kanister Helm repository added to your local setup.

$ helm repo add kanister

Then install the sample MongoDB application with the release name my-release in its own namespace mongo-test using the command below. Make sure you have the kanister controller running in namespace kasten-io which is the default setting in MongoDB charts. Otherwise, you will also have to set the kanister.controller_namespace parameter value to the respective kanister controller namespace in the following command:

# Replace the default s3 credentials (endpoint, bucket and region) with your credentials before you run this command
$ helm install kanister/kanister-mongodb-replicaset -n my-release --namespace mongo-test \
     --set profile.create='true' \
     --set profile.profileName='mongo-test-profile' \
     --set profile.s3.endpoint='https://my-custom-s3-provider:9000' \
     --set profile.s3.accessKey="${AWS_ACCESS_KEY_ID}" \
     --set profile.s3.secretKey="${AWS_SECRET_ACCESS_KEY}" \
     --set profile.s3.bucket='kanister-bucket' \
     --set profile.s3.region=us-west-2

The command deploys MongoDB ReplicaSet on the Kubernetes cluster in the default configuration. The configuration section lists the parameters that can be configured during installation. It also installs a CRD named mongo-test-profile in mongo-test namespace.

The command will also configure a location where artifacts resulting from Kanister data operations such as backup should go. This is stored as a CustomResource (CR) which is then referenced in Kanister ActionSets. Every ActionSet requires a Profile reference whether one created as part of the application install or not. Support for creating an ActionSet as part of install is simply for convenience. This CR can be shared between Kanister-enabled application instances so one option is to only create as part of the first instance.

If not creating a Profile CR, it is possible to use an even simpler command.

$ helm install kanister/kanister-mongodb-replicaset -n my-release --namespace mongo-test

Once MongoDB is running, you can populate it with some data. Let's add a collection called "restaurants" to a test database:

# Connect to MongoDB by running a shell inside MongoDB's pod
$ kubectl exec --namespace mongo-test -i -t my-release-kanister-mongodb-replicaset-0  -- bash -l

# From inside the shell, use the mongo CLI to insert some data into the test database
$ mongo test --quiet --eval "db.restaurants.insert({'name' : 'Roys', 'cuisine' : 'Hawaiian', 'id' : '8675309'})"
WriteResult({ "nInserted" : 1 })

# View the restaurants data in the test database
$ mongo test --quiet --eval "db.restaurants.find()"
{ "_id" : ObjectId("5a1dd0719dcbfd513fecf87c"), "name" : "Roys", "cuisine" : "Hawaiian", "id" : "8675309" }

Protect the Application

You can now take a backup of the MongoDB data using an ActionSet defining backup for this application. Create an ActionSet in the same namespace as the controller.

$ kanctl create actionset --action backup --namespace kasten-io --blueprint my-release-kanister-mongodb-replicaset-blueprint --statefulset mongo-test/my-release-kanister-mongodb-replicaset --profile mongo-test/mongo-test-profile
actionset backup-llfb8 created

$ kubectl --namespace kasten-io get
NAME                 AGE
backup-llfb8         2h

# View the status of the actionset
$ kubectl --namespace kasten-io describe actionset backup-llfb8

Disaster strikes!

Let's say someone with fat fingers accidentally deleted the restaurants collection using the following command:

# Drop the restaurants collection
$ mongo test --quiet --eval "db.restaurants.drop()"

If you try to access this data in the database, you should see that it is no longer there:

$ mongo test --quiet --eval "db.restaurants.find()"
# No entries should be found in the restaurants collection

Restore the Application

To restore the missing data, you should use the backup that you created before. An easy way to do this is to leverage kanctl, a command-line tool that helps create ActionSets that depend on other ActionSets:

$ kanctl --namespace kasten-io create actionset --action restore --from "backup-llfb8"
actionset restore-backup-llfb8-64gqm created

# View the status of the ActionSet
kubectl --namespace kasten-io describe actionset restore-backup-llfb8-64gqm

You should now see that the data has been successfully restored to MongoDB!

$ mongo test --quiet --eval "db.restaurants.find()"
{ "_id" : ObjectId("5a1dd0719dcbfd513fecf87c"), "name" : "Roys", "cuisine" : "Hawaiian", "id" : "8675309" }

Delete the Artifacts

The artifacts created by the backup action can be cleaned up using the following command:

$ kanctl --namespace kasten-io create actionset --action delete --from "backup-llfb8"
actionset "delete-backup-llfb8-k9ncm" created

# View the status of the ActionSet
$ kubectl --namespace kasten-io describe actionset delete-backup-llfb8-k9ncm


If you run into any issues with the above commands, you can check the logs of the controller using:

$ kubectl --namespace kasten-io logs -l app=kanister-operator

Uninstalling the Chart

To uninstall/delete the my-release deployment:

$ helm delete my-release

The command removes all the Kubernetes components associated with the chart and deletes the release. To completely remove the release include the --purge flag.


The following table lists the configurable MongoDB Kanister blueprint and Profile CR parameters and their default values. The Profile CR parameters are passed to the profile sub-chart.

Parameter Description Default
profile.create (Optional) Specify if a Profile CR should be created as part of install. false
profile.defaultProfile (Optional if not creating a default Profile) Set to true to create a profile with name default-profile false
profile.profileName (Required if not creating a default Profile) Name for the profile that is created nil
profile.s3.accessKey (Required if creating profile) API Key for an s3 compatible object store. nil
profile.s3.secretKey (Required if creating profile) Corresponding secret for accessKey. nil
profile.s3.bucket (Required if creating profile) A bucket that will be used to store Kanister artifacts.

The bucket must already exist and the account with the above API key and secret needs to have sufficient permissions to list, get, put, delete.
profile.s3.region (Optional if creating profile) Region to be used for the bucket. nil
profile.s3.endpoint (Optional if creating profile) The URL for an s3 compatible object store provider. Can be omitted if provider is AWS. Required for any other provider. nil
profile.verifySSL (Optional if creating profile) Set to false to disable SSL verification on the s3 endpoint. true
kanister.controller_namespace (Optional) Specify the namespace where the Kanister controller is running. kasten-io

The following tables lists the configurable parameters of the mongodb chart and their default values.

Parameter Description Default
replicas Number of replicas in the replica set 3
replicaSetName The name of the replica set rs0
podDisruptionBudget Pod disruption budget {}
port MongoDB port 27017
installImage.repository Image name for the install container
installImage.tag Image tag for the install container 0.5
installImage.pullPolicy Image pull policy for the init container that establishes the replica set IfNotPresent
image.repository MongoDB image name mongo
image.tag MongoDB image tag 3.6
image.pullPolicy MongoDB image pull policy IfNotPresent
podAnnotations Annotations to be added to MongoDB pods {}
securityContext Security context for the pod {runAsUser: 999, fsGroup: 999, runAsNonRoot: true}
resources Pod resource requests and limits {}
persistentVolume.enabled If true, persistent volume claims are created true
persistentVolume.storageClass Persistent volume storage class
persistentVolume.accessMode Persistent volume access modes [ReadWriteOnce]
persistentVolume.size Persistent volume size 10Gi
persistentVolume.annotations Persistent volume annotations {}
tls.enabled Enable MongoDB TLS support including authentication false
tls.cacert The CA certificate used for the members Our self signed CA certificate
tls.cakey The CA key used for the members Our key for the self signed CA certificate
metrics.enabled Enable Prometheus compatible metrics for pods and replicasets false
metrics.image.repository Image name for metrics exporter ssalaues/mongodb-exporter
metrics.image.tag Image tag for metrics exporter 0.6.1
metrics.image.pullPolicy Image pull policy for metrics exporter IfNotPresent
metrics.port Port for metrics exporter 9216
metrics.path URL Path to expose metrics /metrics
metrics.socketTimeout Time to wait for a non-responding socket 3s
metrics.syncTimeout Time an operation with this session will wait before returning an error 1m
metrics.prometheusServiceDiscovery Adds annotations for Prometheus ServiceDiscovery true
auth.enabled If true, keyfile access control is enabled false
auth.key Key for internal authentication
auth.existingKeySecret If set, an existing secret with this name for the key is used
auth.adminUser MongoDB admin user
auth.adminPassword MongoDB admin password
auth.metricsUser MongoDB clusterMonitor user
auth.metricsPassword MongoDB clusterMonitor password
auth.existingAdminSecret If set, and existing secret with this name is used for the admin user
serviceAnnotations Annotations to be added to the service {}
configmap Content of the MongoDB config file
nodeSelector Node labels for pod assignment {}
affinity Node/pod affinities {}
tolerations List of node taints to tolerate []
livenessProbe Liveness probe configuration See below
readinessProbe Readiness probe configuration See below
extraVars Set environment variables for the main container {}
extraLabels Additional labels to add to resources {}

MongoDB config file

All options that depended on the chart configuration are supplied as command-line arguments to mongod. By default, the chart creates an empty config file. Entries may be added via the configmap configuration value.

Specify each parameter using the --set key=value[,key=value] argument to helm install.

Alternatively, a YAML file that specifies the values for the parameters can be provided while installing the chart. For example,

$ helm install --name my-release -f values.yaml kanister/kanister-mongodb-replicaset

Tip: You can use the default values.yaml

Once you have all 3 nodes in running, you can run the "" script in this directory, which will insert a key into the primary and check the secondaries for output. This script requires that the $RELEASE_NAME environment variable be set, in order to access the pods.


By default, this chart creates a MongoDB replica set without authentication. Authentication can be enabled using the parameter auth.enabled. Once enabled, keyfile access control is set up and an admin user with root privileges is created. User credentials and keyfile may be specified directly. Alternatively, existing secrets may be provided. The secret for the admin user must contain the keys user and password, that for the key file must contain key.txt. The user is created with full root permissions but is restricted to the admin database for security purposes. It can be used to create additional users with more specific permissions.

TLS support

To enable full TLS encryption set tls.enabled to true. It is recommended to create your own CA by executing:

$ openssl genrsa -out ca.key 2048
$ openssl req -x509 -new -nodes -key ca.key -days 10000 -out ca.crt -subj "/"

After that paste the base64 encoded (cat ca.key | base64 -w0) cert and key into the fields tls.cacert and tls.cakey. Adapt the configmap for the replicaset as follows:

    dbPath: /data/db
    port: 27017
      mode: requireSSL
      CAFile: /ca/tls.crt
      PEMKeyFile: /work-dir/mongo.pem
    replSetName: rs0
    authorization: enabled
    clusterAuthMode: x509
    keyFile: /keydir/key.txt

To access the cluster you need one of the certificates generated during cluster setup in /work-dir/mongo.pem of the certain container or you generate your own one via:

$ cat >openssl.cnf <<EOL
req_extensions = v3_req
distinguished_name = req_distinguished_name
[ v3_req ]
basicConstraints = CA:FALSE
keyUsage = nonRepudiation, digitalSignature, keyEncipherment
subjectAltName = @alt_names
$ openssl genrsa -out mongo.key 2048
$ openssl req -new -key mongo.key -out mongo.csr -subj "/CN=$HOSTNAME" -config openssl.cnf
$ openssl x509 -req -in mongo.csr \
    -CA $MONGOCACRT -CAkey $MONGOCAKEY -CAcreateserial \
    -out mongo.crt -days 3650 -extensions v3_req -extfile openssl.cnf
$ rm mongo.csr
$ cat mongo.crt mongo.key > mongo.pem
$ rm mongo.key mongo.crt

Please ensure that you exchange the $HOSTNAME with your actual hostname and the $HOSTNAME1, $HOSTNAME2, etc. with alternative hostnames you want to allow access to the MongoDB replicaset. You should now be able to authenticate to the mongodb with your mongo.pem certificate:

$ mongo --ssl --sslCAFile=ca.crt --sslPEMKeyFile=mongo.pem --eval "db.adminCommand('ping')"

Promethus metrics

Enabling the metrics as follows will allow for each replicaset pod to export Prometheus compatible metrics on server status, individual replicaset information, replication oplogs, and storage engine.

  enabled: true
    repository: ssalaues/mongodb-exporter
    tag: 0.6.1
    pullPolicy: IfNotPresent
  port: 9216
  path: "/metrics"
  socketTimeout: 3s
  syncTimeout: 1m
  prometheusServiceDiscovery: true
  resources: {}

More information on MongoDB Exporter metrics available.

Readiness probe

The default values for the readiness probe are:

  initialDelaySeconds: 5
  timeoutSeconds: 1
  failureThreshold: 3
  periodSeconds: 10
  successThreshold: 1

Liveness probe

The default values for the liveness probe are:

  initialDelaySeconds: 30
  timeoutSeconds: 5
  failureThreshold: 3
  periodSeconds: 10
  successThreshold: 1

Deep dive

Because the pod names are dependent on the name chosen for it, the following examples use the environment variable RELEASENAME. For example, if the helm release name is messy-hydra, one would need to set the following before proceeding. The example scripts below assume 3 pods only.

export RELEASE_NAME=messy-hydra

Cluster Health

$ for i in 0 1 2; do kubectl exec $RELEASE_NAME-kanister-mongodb-replicaset-$i -- sh -c 'mongo --eval="printjson(db.serverStatus())"'; done


One can check the roles being played by each node by using the following:

$ for i in 0 1 2; do kubectl exec $RELEASE_NAME-kanister-mongodb-replicaset-$i -- sh -c 'mongo --eval="printjson(rs.isMaster())"'; done

MongoDB shell version: 3.6.3
connecting to: mongodb://
MongoDB server version: 3.6.3
	"hosts" : [
	"setName" : "rs0",
	"setVersion" : 3,
	"ismaster" : true,
	"secondary" : false,
	"primary" : "messy-hydra-mongodb-0.messy-hydra-mongodb.default.svc.cluster.local:27017",
	"me" : "messy-hydra-mongodb-0.messy-hydra-mongodb.default.svc.cluster.local:27017",
	"electionId" : ObjectId("7fffffff0000000000000001"),
	"maxBsonObjectSize" : 16777216,
	"maxMessageSizeBytes" : 48000000,
	"maxWriteBatchSize" : 1000,
	"localTime" : ISODate("2016-09-13T01:10:12.680Z"),
	"maxWireVersion" : 4,
	"minWireVersion" : 0,
	"ok" : 1

This lets us see which member is primary.

Let us now test persistence and failover. First, we insert a key (in the below example, we assume pod 0 is the master):

$ kubectl exec $RELEASE_NAME-kanister-mongodb-replicaset-0 -- mongo --eval="printjson(db.test.insert({key1: 'value1'}))"

MongoDB shell version: 3.6.3
connecting to: mongodb://
{ "nInserted" : 1 }

Watch existing members:

$ kubectl run --attach bbox --image=mongo:3.6 --restart=Never --env="RELEASE_NAME=$RELEASE_NAME" -- sh -c 'while true; do for i in 0 1 2; do echo $RELEASE_NAME-kanister-mongodb-replicaset-$i $(mongo --host=$RELEASE_NAME-kanister-mongodb-replicaset-$i.$RELEASE_NAME-kanister-mongodb-replicaset --eval="printjson(rs.isMaster())" | grep primary); sleep 1; done; done';

Waiting for pod default/bbox2 to be running, status is Pending, pod ready: false
If you don't see a command prompt, try pressing enter.
messy-hydra-mongodb-2 "primary" : "messy-hydra-mongodb-0.messy-hydra-mongodb.default.svc.cluster.local:27017",
messy-hydra-mongodb-0 "primary" : "messy-hydra-mongodb-0.messy-hydra-mongodb.default.svc.cluster.local:27017",
messy-hydra-mongodb-1 "primary" : "messy-hydra-mongodb-0.messy-hydra-mongodb.default.svc.cluster.local:27017",
messy-hydra-mongodb-2 "primary" : "messy-hydra-mongodb-0.messy-hydra-mongodb.default.svc.cluster.local:27017",
messy-hydra-mongodb-0 "primary" : "messy-hydra-mongodb-0.messy-hydra-mongodb.default.svc.cluster.local:27017",

Kill the primary and watch as a new master getting elected.

$ kubectl delete pod $RELEASE_NAME-kanister-mongodb-replicaset-0

pod "messy-hydra-mongodb-0" deleted

Delete all pods and let the statefulset controller bring it up.

$ kubectl delete po -l "app=kanister-mongodb-replicaset,release=$RELEASE_NAME"
$ kubectl get po --watch-only
NAME                    READY     STATUS        RESTARTS   AGE
messy-hydra-mongodb-0   0/1       Pending   0         0s
messy-hydra-mongodb-0   0/1       Pending   0         0s
messy-hydra-mongodb-0   0/1       Pending   0         7s
messy-hydra-mongodb-0   0/1       Init:0/2   0         7s
messy-hydra-mongodb-0   0/1       Init:1/2   0         27s
messy-hydra-mongodb-0   0/1       Init:1/2   0         28s
messy-hydra-mongodb-0   0/1       PodInitializing   0         31s
messy-hydra-mongodb-0   0/1       Running   0         32s
messy-hydra-mongodb-0   1/1       Running   0         37s
messy-hydra-mongodb-1   0/1       Pending   0         0s
messy-hydra-mongodb-1   0/1       Pending   0         0s
messy-hydra-mongodb-1   0/1       Init:0/2   0         0s
messy-hydra-mongodb-1   0/1       Init:1/2   0         20s
messy-hydra-mongodb-1   0/1       Init:1/2   0         21s
messy-hydra-mongodb-1   0/1       PodInitializing   0         24s
messy-hydra-mongodb-1   0/1       Running   0         25s
messy-hydra-mongodb-1   1/1       Running   0         30s
messy-hydra-mongodb-2   0/1       Pending   0         0s
messy-hydra-mongodb-2   0/1       Pending   0         0s
messy-hydra-mongodb-2   0/1       Init:0/2   0         0s
messy-hydra-mongodb-2   0/1       Init:1/2   0         21s
messy-hydra-mongodb-2   0/1       Init:1/2   0         22s
messy-hydra-mongodb-2   0/1       PodInitializing   0         25s
messy-hydra-mongodb-2   0/1       Running   0         26s
messy-hydra-mongodb-2   1/1       Running   0         30s

messy-hydra-mongodb-0 "primary" : "messy-hydra-mongodb-0.messy-hydra-mongodb.default.svc.cluster.local:27017",
messy-hydra-mongodb-1 "primary" : "messy-hydra-mongodb-0.messy-hydra-mongodb.default.svc.cluster.local:27017",
messy-hydra-mongodb-2 "primary" : "messy-hydra-mongodb-0.messy-hydra-mongodb.default.svc.cluster.local:27017",

Check the previously inserted key:

$ kubectl exec $RELEASE_NAME-kanister-mongodb-replicaset-1 -- mongo --eval="rs.slaveOk(); db.test.find({key1:{\$exists:true}}).forEach(printjson)"

MongoDB shell version: 3.6.3
connecting to: mongodb://
{ "_id" : ObjectId("57b180b1a7311d08f2bfb617"), "key1" : "value1" }


Scaling should be managed by helm upgrade, which is the recommended way.