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Run MongoDB with Custom PodTemplate

KubeDB supports providing custom configuration for MongoDB via PodTemplate. This tutorial will show you how to use KubeDB to run a MongoDB database with custom configuration using PodTemplate.

Before You Begin

  • At first, you need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. 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 demo throughout this tutorial.

    $ kubectl create ns demo
    namespace/demo created
    

Note: YAML files used in this tutorial are stored in docs/examples/mongodb folder in GitHub repository kubedb/docs.

Overview

KubeDB allows providing a template for database pod through spec.podTemplate. KubeDB operator will pass the information provided in spec.podTemplate to the StatefulSet created for MongoDB database.

KubeDB accept following fields to set in spec.podTemplate:

  • metadata:
    • annotations (pod’s annotation)
  • controller:
    • annotations (statefulset’s annotation)
  • spec:
    • args
    • env
    • resources
    • initContainers
    • imagePullSecrets
    • nodeSelector
    • affinity
    • schedulerName
    • tolerations
    • priorityClassName
    • priority
    • securityContext

Read about the fields in details in PodTemplate concept,

CRD Configuration

Below is the YAML for the MongoDB created in this example. Here, spec.podTemplate.spec.env specifies environment variables and spec.podTemplate.spec.args provides extra arguments for MongoDB Docker Image.

In this tutorial, maxIncomingConnections is set to 100 (default, 65536) through args --maxConns=100.

apiVersion: kubedb.com/v1alpha2
kind: MongoDB
metadata:
  name: mgo-misc-config
  namespace: demo
spec:
  version: "3.6-v3"
  storageType: "Durable"
  storage:
    storageClassName: "standard"
    accessModes:
    - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
  podTemplate:
    spec:
      args:
      - --maxConns=100
      resources:
        requests:
          memory: "1Gi"
          cpu: "250m"
  terminationPolicy: Halt
$ kubectl create -f https://github.com/kubedb/docs/raw/v2020.11.12/docs/examples/mongodb/configuration/mgo-misc-config.yaml
mongodb.kubedb.com/mgo-misc-config created

Now, wait a few minutes. KubeDB operator will create necessary PVC, statefulset, services, secret etc. If everything goes well, we will see that a pod with the name mgo-misc-config-0 has been created.

Check that the statefulset’s pod is running

$ kubectl get pod -n demo
NAME                READY     STATUS    RESTARTS   AGE
mgo-misc-config-0   1/1       Running   0          14m

Now, check if the database has started with the custom configuration we have provided.

Now, you can connect to this database through mongo-shell. In this tutorial, we are connecting to the MongoDB server from inside the pod.

$ kubectl get secrets -n demo mgo-misc-config-auth -o jsonpath='{.data.\username}' | base64 -d
root

$ kubectl get secrets -n demo mgo-misc-config-auth -o jsonpath='{.data.\password}' | base64 -d
zyp5hDfRlVOWOyk9

$ kubectl exec -it mgo-misc-config-0 -n demo sh

> mongo admin

> db.auth("root","zyp5hDfRlVOWOyk9")
1

> db._adminCommand( {getCmdLineOpts: 1})
{
	"argv" : [
		"mongod",
		"--dbpath=/data/db",
		"--auth",
		"--bind_ip=0.0.0.0",
		"--port=27017",
		"--maxConns=100"
	],
	"parsed" : {
		"net" : {
			"bindIp" : "0.0.0.0",
			"maxIncomingConnections" : 100,
			"port" : 27017
		},
		"security" : {
			"authorization" : "enabled"
		},
		"storage" : {
			"dbPath" : "/data/db"
		}
	},
	"ok" : 1
}

> exit
bye

You can see the maximum connection is set to 100 in parsed.net.maxIncomingConnections.

Cleaning up

To cleanup the Kubernetes resources created by this tutorial, run:

kubectl patch -n demo mg/mgo-misc-config -p '{"spec":{"terminationPolicy":"WipeOut"}}' --type="merge"
kubectl delete -n demo mg/mgo-misc-config

kubectl patch -n demo drmn/mgo-misc-config -p '{"spec":{"wipeOut":true}}' --type="merge"
kubectl delete -n demo drmn/mgo-misc-config

kubectl delete ns demo

If you would like to uninstall KubeDB operator, please follow the steps here.

Next Steps