Kubernetes Crashloopbackoff With Minikube - node.js

Question

So I am learning about Kubernetes with a guide, I am trying to deploy a MongoDB Pod with 1 replica. This is the deployment config file.
apiVersion: apps/v1
kind: Deployment
metadata:
name: mongodb-deployment
labels:
app: mongodb
spec:
replicas: 1
selector:
matchLabels:
app: mongodb
template:
metadata:
labels:
app: mongodb
spec:
containers:
- name: mongodb
image: mongo
ports:
- containerPort: 27017
env:
- name: MONGO_INITDB_ROOT_USERNAME
valueFrom:
secretKeyRef:
name: mongodb-secret
key: mongo-root-username
- name: MONGO_INITDB_ROOT_PASSWORD
valueFrom:
secretKeyRef:
name: mongodb-secret
key: mongo-root-password
---
apiVersion: v1
kind: Service
metadata:
name: mongodb-service
spec:
selector:
app: mongodb
ports:
- protocol: TCP
port: 27017
targetPort: 27017
I also try to deploy a Mongo-Express Pod with almost the same config file, but I keep getting CrashLoopBackOff for both Pods, From the little understanding I have, this is caused by the container failing and restarting in a cycle. I tried going through the events with kubectl get events and I see that a warning with message Back-off restarting failed container keeps occurring. I also tried doing a little digging around and came across a solution that says to add
command: ['sleep']
args: ['infinity']
That fixed the CrashLoopBackOff issue, but when I try to get the logs for the Pod, nothing is displayed on the terminal. Please I need some help and possible explanation as how the command and args seem to fix it, also how do I stop this crash from happening to my Pods and current one, Thank you very much.

Answer 1

My advice is to deploy MongoDB as StatefulSet on Kubernetes.
In stateful application, the N-replicas of master nodes manages several worker nodes under a cluster. So, if any master node goes down the other ordinal instances will be active to execute the workflow. The master node instances must be identified as a unique ordinal number known as StatefulSet.
See more: mongodb-sts, mongodb-on-kubernetes.
Also use Headless service to manage the domain of a Pod. In general understanding of Headless Service, there is no need for LoadBalancer or a kube-proxy to interact directly with Pods but using a Service IP, so the Cluster IP is set to none.
In your case:
apiVersion: v1
kind: Service
metadata:
name: mongodb
spec:
clusterIP: None
selector:
app: mongodb
ports:
- port: 27017
The error:
Also uncaught exception: Error: couldn't add user: Error preflighting normalization: U_STRINGPREP_PROHIBITED_ERROR _getErrorWithCode#src/mongo/shell/utils.js:25:13
indicates that the secret may be missing. Take a look: mongodb-initializating.
In your case secret should look similar:
apiVersion: v1
kind: Secret
metadata:
name: mongodb-secret
type: Opaque
data:
mongo-root-username: YWRtaW4=
mongo-root-password: MWYyZDFlMmU2N2Rm
Remember to configure also a volume for your pods - follow tutorials I have linked above.

Answer 2

Deploy mongodb with StatefulSet not as deployment.
Example:
apiVersion: v1
kind: Service
metadata:
name: mongodb-service
labels:
name: mongo
spec:
ports:
port: 27017
targetPort: 27017
clusterIP: None
selector:
role: mongo
apiVersion: apps/v1beta1
kind: StatefulSet
metadata:
name: mongod
spec:
serviceName: mongodb-service
replicas: 3
template:
metadata:
labels:
role: mongo
environment: test
replicaset: MainRepSet
spec:
affinity:
podAntiAffinity:
preferredDuringSchedulingIgnoredDuringExecution:
- weight: 100
podAffinityTerm:
labelSelector:
matchExpressions:
- key: replicaset
operator: In
values:
- MainRepSet
topologyKey: kubernetes.io/hostname
terminationGracePeriodSeconds: 10
volumes:
- name: secrets-volume
secret:
secretName: shared-bootstrap-data
defaultMode: 256
containers:
- name: mongod-container
#image: pkdone/mongo-ent:3.4
image: mongo
command:
- "numactl"
- "--interleave=all"
- "mongod"
- "--wiredTigerCacheSizeGB"
- "0.1"
- "--bind_ip"
- "0.0.0.0"
- "--replSet"
- "MainRepSet"
- "--auth"
- "--clusterAuthMode"
- "keyFile"
- "--keyFile"
- "/etc/secrets-volume/internal-auth-mongodb-keyfile"
- "--setParameter"
- "authenticationMechanisms=SCRAM-SHA-1"
resources:
requests:
cpu: 0.2
memory: 200Mi
ports:
- containerPort: 27017
volumeMounts:
- name: secrets-volume
readOnly: true
mountPath: /etc/secrets-volume
- name: mongodb-persistent-storage-claim
mountPath: /data/db
volumeClaimTemplates:
metadata:
name: mongodb-persistent-storage-claim
annotations:
volume.beta.kubernetes.io/storage-class: "standard"
spec:
accessModes: [ "ReadWriteOnce" ]
resources:
requests:
storage: 1Gi