How to pass environment variables to a service in kubernetes? - mongodb

Question

I have configured minikube and am trying to run kubenetes on my local ubuntu machine.
When I build the MongoDB docker image on my local, I can pass the env variables this way and it works well with the backend API:
mongo_db:
image: mongo:latest
container_name: db_container
environment:
- MONGODB_INITDB_DATABASE=contacts
- MONGO_INITDB_ROOT_USERNAME=root
- MONGO_INITDB_ROOT_PASSWORD=password
ports:
- 27017:27017
volumes:
- ./mongodb_data_container:/data/db
But when I try to run the entire application(frontend, backend, and MongoDB) in Kubernetes, how do I initiate the MongoDB with the env variables so the backend API can connect to the database pod instance? I'm pulling latest mongodb instance, here's the mongo-deployment yaml file:
# MongoDB Deployment - Database
apiVersion: apps/v1
kind: Deployment
metadata:
name: mongo
spec:
selector:
matchLabels:
app: mern-stack
replicas: 1
template:
metadata:
labels:
app: mern-stack
spec:
containers:
- name: mern-stack
image: mongo:latest
ports:
- containerPort: 27017
volumeMounts:
- name: db-data
mountPath: /data
readOnly: false
volumes:
- name: db-data
persistentVolumeClaim:
claimName: mern-stack-data
I have tried to pass the env variables this way, but it doesn't seem to work:
...
volumeMounts:
- name: db-data
mountPath: /data
readOnly: false
env:
- name: MONGODB_INITDB_DATABASE
value: "contacts"
- name: MONGO_INITDB_ROOT_USERNAME
value: "root"
- name: MONGO_INITDB_ROOT_PASSWORD
value: "password"
...
What's the quick solution? Should I try config map and secret eventually?

Answer 1

volumeMounts usually used for the whole config file e.g. ***.conf
It's more convenient for you to use secret in your case.
1、create secret resource
apiVersion: v1
data:
db_url: YWRtaW4=
db_password: MWYyZDFlMmU2N2Rm
kind: Secret
metadata:
name: <secretname>
namespace: <namespaceuwant>
type: Opaque
2、you can use in your mongodb
mongo_db:
image: mongo:latest
container_name: db_container
env:
- name: db_url # env you can get
valueFrom:
secretKeyRef:
name: <secretname> # step 1 create
key: db_url # in your secret
.
.
.

Answer 2

Configure kubectl to default to your namespace.
If you have not already, run the following command to execute all kubectl commands in the namespace you created:
kubectl config set-context $(kubectl config current-context) --namespace=<metadata.namespace>
You can choose to use a cleartext password:
apiVersion: v1
kind: Secret
metadata:
name: <mms-user-1-password>
# corresponds to user.spec.passwordSecretKeyRef.name
type: Opaque
stringData:
password: <my-plain-text-password>
# corresponds to user.spec.passwordSecretKeyRef.key
data:
password: <base-64-encoded-password>
# corresponds to user.spec.passwordSecretKeyRef.key
...
or you can choose to use a Base64-encoded password:
---
apiVersion: v1
kind: Secret
metadata:
name: <mms-user-1-password>
# corresponds to user.spec.passwordSecretKeyRef.name
type: Opaque
stringData:
password: <my-plain-text-password>
# corresponds to user.spec.passwordSecretKeyRef.key
data:
password: <base-64-encoded-password>
# corresponds to user.spec.passwordSecretKeyRef.key
...
Create a new User Secret YAML file.
To learn about your options for secret storage, see
https://kubernetes.io/docs/concepts/configuration/secret/
Change these values to yours.
stringData.password #Plaintext password for the desired user.
data.password #Base64-encoded password for the desired user.
Save the User Secret file with a .yaml extension
Create MongoDBUser
Copy the following example MongoDBUser
apiVersion: mongodb.com/v1
kind: MongoDBUser
metadata:
name: <mms-scram-user-1>
spec:
passwordSecretKeyRef:
name: <mms-user-1-password>
# Match to metadata.name of the User Secret
key: password
username: "<mms-scram-user-1>"
db: "admin" #
mongodbResourceRef:
name: "<my-replica-set>"
# Match to MongoDB resource using authenticaiton
roles:
- db: "admin"
name: "clusterAdmin"
- db: "admin"
name: "userAdminAnyDatabase"
- db: "admin"
name: "readWrite"
- db: "admin"
name: "userAdminAnyDatabase"
...
Add your own fields.
Add any additional roles for the user to the MongoDBUser.
Invoke the following Kubernetes command to create your database user:
kubectl apply -f <database-user-conf>.yaml
When you create a new MongoDB database user, Kubernetes Operator automatically creates a new Kubernetes secret. The Kubernetes secret contains the following information about the new database user:
username: Username for the database user
password: Password for the database user
connectionString.standard: Standard connection string that can connect you to the database as this database user.
connectionString.standardSrv: DNS seed list connection string that can connect you to the database as this database user.
For more details, you can visit here

Answer 3

You can populate a container's environment variables through the use of Secrets or ConfigMaps. Use Secrets when the data you are working with is sensitive (e.g. passwords), and ConfigMaps when it is not.
In your Pod definition specify that the container should pull values from a Secret:
apiVersion: v1
kind: Pod
metadata:
labels:
context: docker-k8s-lab
name: mongo-pod
name: mongo-pod
spec:
containers:
- image: "mongo:latest"
name: mongo
ports:
- containerPort: 3306
envFrom:
- secretRef:
name: mongo-secret
You can now define two different Secrets, one for production and one for dev.
dev-secret.yaml:
apiVersion: v1
kind: Secret
metadata:
name: mongo-secret
type: Opaque
data:
MYSQL_USER: bXlzcWwK
MYSQL_PASSWORD: bXlzcWwK
MYSQL_DATABASE: c2FtcGxlCg==
MYSQL_ROOT_PASSWORD: c3VwZXJzZWNyZXQK
prod-secret.yaml:
apiVersion: v1
kind: Secret
metadata:
name: mongo-secret
type: Opaque
data:
MYSQL_USER: am9obgo=
MYSQL_PASSWORD: c2VjdXJlCg==
MYSQL_DATABASE: cHJvZC1kYgo=
MYSQL_ROOT_PASSWORD: cm9vdHkK
And deploy the correct secret to the correct Kubernetes cluster:
kubectl config use-context dev
kubectl create -f dev-secret.yaml
kubectl config use-context prod
kubectl create -f prod-secret.yaml
Now whenever a Pod starts it will populate its environment variables from the values specified in the Secret.