Troubleshoot Deployment issues in Kubernetes.md

Problem Statement

The Nautilus DevOps team is facing issues with their Redis application deployment on Kubernetes. The pods are not running due to errors related to the container image and ConfigMap.

Solution

1. Identify the Issues

Pod Status:

kubectl get pods

Output:

NAME                                READY   STATUS              RESTARTS   AGE
redis-deployment-54cdf4f76d-lvj2m   0/1     ContainerCreating   0          52s

Deployment Description:

kubectl describe deployments.apps redis-deployment

Output:

Name:                   redis-deployment
Namespace:              default
CreationTimestamp:      Tue, 30 Jul 2024 04:46:52 +0000
Labels:                 app=redis
Annotations:            deployment.kubernetes.io/revision: 1
Selector:               app=redis
Replicas:               1 desired | 1 updated | 1 total | 0 available | 1 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=redis
  Containers:
   redis-container:
    Image:      redis:alpin  # Error: Typo in image name
    Port:       6379/TCP
    Host Port:  0/TCP
    Requests:
      cpu:        300m
    Environment:  <none>
    Mounts:
      /redis-master from config (rw)
      /redis-master-data from data (rw)
  Volumes:
   data:
    Type:       EmptyDir (a temporary directory that shares a pod's lifetime)
    Medium:
    SizeLimit:  <unset>
   config:
    Type:          ConfigMap (a volume populated by a ConfigMap)
    Name:          redis-conig  # Error: Typo in ConfigMap name
    Optional:      false
  Node-Selectors:  <none>
  Tolerations:     <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      False   MinimumReplicasUnavailable
  Progressing    True    ReplicaSetUpdated
OldReplicaSets:  <none>
NewReplicaSet:   redis-deployment-54cdf4f76d (1/1 replicas created)
Events:
  Type    Reason             Age   From                   Message
  ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  98s   deployment-controller  Scaled up replica set redis-deployment-54cdf4f76d to 1
  Warning FailedMount       90s   kubelet, node1          MountVolume.SetUp failed for volume "config" : configmap "redis-conig" not found
  Warning FailedMount       69s   kubelet, node1          Unable to attach or mount volumes: unmounted volumes=[config], unattached volumes=[], failed to process volumes=[]: timed out waiting for the condition

Issues Identified:

1. Image Name Typo: The image specified is redis:alpin instead of redis:alpine.
2. ConfigMap Name Typo: The ConfigMap specified is redis-conig instead of redis-config.

2. Fix the Deployment

Update the Deployment:

To fix the issues, you need to update the deployment configuration. First, create a corrected YAML file or edit the deployment directly.

Edit the Deployment:

kubectl edit deployment redis-deployment

Update the following fields in the editor:

spec:
  containers:
  - name: redis-container
    image: redis:alpine  # Corrected image name
  volumes:
  - name: config
    configMap:
      name: redis-config  # Corrected ConfigMap name

Apply the Updated Configuration:

Alternatively, you can apply a corrected YAML configuration file. Create or edit the file named redis-deployment-corrected.yaml with the following content:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: redis-deployment
  namespace: default
spec:
  replicas: 1
  selector:
    matchLabels:
      app: redis
  template:
    metadata:
      labels:
        app: redis
    spec:
      containers:
      - name: redis-container
        image: redis:alpine
        ports:
        - containerPort: 6379
        volumeMounts:
        - name: config
          mountPath: /redis-master
        - name: data
          mountPath: /redis-master-data
      volumes:
      - name: config
        configMap:
          name: redis-config
      - name: data
        emptyDir: {}

Apply the Updated YAML:

kubectl apply -f redis-deployment-corrected.yaml

3. Verify the Fix

Check Pods Status:

kubectl get pods

Verify Pod Details:

kubectl describe pods redis-deployment-54cdf4f76d-<pod-suffix>

Check Events:

kubectl get events

By following these steps, the issues with the Redis deployment should be resolved, and the pods should be running as expected.