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Kubernetes Level 02 Day 11: Fix Issue with LAMP Environment

This document outlines the troubleshooting and resolution process for Kubernetes Level 02 Day 11. A WordPress application running on a LAMP stack inside a Kubernetes cluster stopped working after previously functioning correctly. Investigation revealed multiple configuration issues including incorrect service ports and application code referencing wrong environment variables.

Table of Contents

Task Overview

Objective: Restore the functionality of the WordPress LAMP application deployed in Kubernetes.

The application was previously accessible but stopped working due to configuration and application-level issues.

Deployment Details

Resource Name
Deployment lamp-wp
Service lamp-service
Database Service mysql-service
HTTP Port 80
Expected NodePort 30008

Observed Problems

  1. The NodePort configured in the service was incorrect.
  2. The application could not connect to the MySQL database.
  3. The PHP application file referenced incorrect environment variable names.

Troubleshooting Process

1. Inspect Cluster Resources

First, verify the running resources in the cluster.

kubectl get pods,deployments,services

Example output:

NAME                           READY   STATUS
pod/lamp-wp-5594699b75-67xrz   2/2     Running

NAME                      READY
deployment.apps/lamp-wp   1/1

NAME               TYPE       PORT(S)
lamp-service       NodePort   80:30009/TCP
mysql-service      ClusterIP  3306/TCP

Observation:

The NodePort was incorrectly set to 30009 instead of 30008.

2. Analyze Service Configuration

Export the service configuration to a YAML file.

kubectl get svc lamp-service -o yaml > lamp-svc.yml

Edit the file:

vi lamp-svc.yml

Fix the following values:

nodePort: 30008
port: 80
targetPort: 80

Apply the changes.

kubectl apply -f lamp-svc.yml

Verify:

kubectl get svc

Expected output:

lamp-service   NodePort   80:30008/TCP

3. Inspect Container Logs

The pod contains two containers:

  • HTTP container (Apache + PHP)
  • MySQL container

Retrieve the container names.

HTTP=$(kubectl get pod -o=jsonpath='{.items[*].spec.containers[0].name}')
MYSQL=$(kubectl get pod -o=jsonpath='{.items[*].spec.containers[1].name}')
POD=$(kubectl get pods -o=jsonpath='{.items[*].metadata.name}')

Check the HTTP container logs.

kubectl logs -f $POD -c $HTTP

Logs indicated that the application was failing to connect to the database.

4. Investigate Application Code

Access the HTTP container shell.

kubectl exec -it $POD -c $HTTP -- sh

Navigate to the application directory.

cd /app
ls

The main application file is:

index.php

Display the file.

cat index.php

Incorrect variables were found:

$dbpass = $_ENV['MYSQL_PASSWORDS'];
$dbhost = $_ENV['HOST_MYQSL'];

These names do not match the environment variables provided by Kubernetes.

Step-by-Step Solution

1. Fix NodePort Configuration

Ensure the service exposes the correct port.

kubectl get svc lamp-service

Correct configuration:

80:30008/TCP

2. Identify Containers and Pod Name

HTTP=$(kubectl get pod -o=jsonpath='{.items[*].spec.containers[0].name}')
MYSQL=$(kubectl get pod -o=jsonpath='{.items[*].spec.containers[1].name}')
POD=$(kubectl get pods -o=jsonpath='{.items[*].metadata.name}')

3. Correct Environment Variable Usage in PHP

Edit the PHP file.

vi /app/index.php

Fix the incorrect variables.

Before

$dbpass = $_ENV['MYSQL_PASSWORDS'];
$dbhost = $_ENV['HOST_MYQSL'];

After

$dbpass = $_ENV['MYSQL_PASSWORD'];
$dbhost = $_ENV['MYSQL_HOST'];

These variables correspond to the Kubernetes secrets injected into the pod.

4. Restart PHP Service

Restart the PHP-FPM process inside the container.

service php-fpm restart

Verify status.

service php-fpm status

Expected output:

php-fpmd RUNNING

Exit the container.

exit

5. Verification

Confirm environment variables inside both containers.

HTTP container:

kubectl exec -it $POD -c $HTTP -- env | grep -i mysql

MySQL container:

kubectl exec -it $POD -c $MYSQL -- env | grep -i mysql

Expected variables:

MYSQL_DATABASE
MYSQL_USER
MYSQL_PASSWORD
MYSQL_HOST
MYSQL_ROOT_PASSWORD

When accessing the application URL through the NodePort, the page should display:

Connected successfully

Deep Dive: Debugging Multi-Container Pods

Service Port Misconfiguration

A Kubernetes NodePort service exposes an application externally. If the NodePort is incorrect, traffic will never reach the application container.

Correct mapping:

NodePort → Service Port → Container Port
30008   → 80           → 80

Environment Variable Issues

Applications often depend on environment variables injected by Kubernetes secrets or ConfigMaps.

Example:

MYSQL_HOST
MYSQL_USER
MYSQL_PASSWORD
MYSQL_DATABASE

If the application code references incorrect variable names, the connection to external services such as databases will fail even if the infrastructure is correct.

Why Application-Level Debugging Matters

Many Kubernetes troubleshooting scenarios involve not only infrastructure configuration but also application logic.

Typical debugging workflow:

  1. Verify Kubernetes resources.
  2. Inspect service configuration.
  3. Check container logs.
  4. Inspect environment variables.
  5. Debug application code inside the container.

This layered approach helps quickly isolate whether the issue is related to Kubernetes configuration or application behavior.