Troubleshooting Application Failure Solution

  • Troubleshooting Test 1: A simple 2 tier application is deployed in the alpha namespace. It must display a green web page on success. Click on the App tab at the top of your terminal to view your application. It is currently failed. Troubleshoot and fix the issue.

Stick to the given architecture. Use the same names and port numbers as given in the below architecture diagram. Feel free to edit, delete or recreate objects as necessary.

The service name used for the MySQL Pod is incorrect. According to the Architecture diagram, it should be mysql-service.

To fix this, first delete the current service: kubectl -n alpha delete svc mysql

Then create a new service with the following YAML file (or use imperative command):

---
apiVersion: v1
kind: Service
metadata:
  name: mysql-service
  namespace: alpha
spec:
    ports:
    - port: 3306
      targetPort: 3306
    selector:
      name: mysql


Create the new service: kubectl create -f <service.yaml>
  • Troubleshooting Test 2: The same 2 tier application is deployed in the beta namespace. It must display a green web page on success. Click on the App tab at the top of your terminal to view your application. It is currently failed. Troubleshoot and fix the issue.

Stick to the given architecture. Use the same names and port numbers as given in the below architecture diagram. Feel free to edit, delete or recreate objects as necessary.

* Troubleshooting Test 3: The same 2 tier application is deployed in the gamma namespace. It must display a green web page on success. Click on the App tab at the top of your terminal to view your application. It is currently failed or unresponsive. Troubleshoot and fix the issue.

Stick to the given architecture. Use the same names and port numbers as given in the below architecture diagram. Feel free to edit, delete or recreate objects as necessary.


If you inspect the mysql-service, you will see that that the selector used does not match the label on the mysql pod.

Service:

root@controlplane:~# kubectl -n gamma describe svc mysql-service | grep -i selector
Selector:          name=sql00001
root@controlplane:~#

Pod:

root@controlplane:~# kubectl -n gamma describe pod mysql | grep -i label   
Labels:       name=mysql
root@controlplane:~#

As you can see the selector used is name=sql001 whereas it should be name=mysql.
Update the mysql-service to use the correct selector as per the below YAML:

---
apiVersion: v1
kind: Service
metadata:
  name: mysql-service
  namespace: gamma
spec:
    ports:
    - port: 3306
      targetPort: 3306
    selector:
      name: mysql


* Troubleshooting Test 4: The same 2 tier application is deployed in the delta namespace. It must display a green web page on success. Click on the App tab at the top of your terminal to view your application. It is currently failed. Troubleshoot and fix the issue.

Stick to the given architecture. Use the same names and port numbers as given in the below architecture diagram. Feel free to edit, delete or recreate objects as necessary.

Try accessing the web application from the browser using the tab called app. You will notice that it cannot connect to the MySQL database:

Environment Variables: DB_Host=mysql-service; DB_Database=Not Set; DB_User=sql-user; DB_Password=paswrd; 1045 (28000): Access denied for user ‘sql-user’@’10.244.1.9’ (using password: YES)

According to the architecture diagram, the DB_User should be root but it is set to sql-user in the webapp-mysql deployment.

Use the command kubectl -n delta edit deployments.apps webapp-mysql and update the environment variable as follows:

spec: containers: - env: - name: DB_Host value: mysql-service - name: DB_User value: root - name: DB_Password value: paswrd

This will recreate the pod and you should then be able to access the application.

* Troubleshooting Test 5: The same 2 tier application is deployed in the epsilon namespace. It must display a green web page on success. Click on the App tab at the top of your terminal to view your application. It is currently failed. Troubleshoot and fix the issue.

Stick to the given architecture. Use the same names and port numbers as given in the below architecture diagram. Feel free to edit, delete or recreate objects as necessary.

If you inspect the environment variable called MYSQL_ROOT_PASSWORD, you will notice that the value is incorrect as compared to the architecture diagram: -

root@controlplane:~# kubectl -n epsilon describe pod mysql | grep MYSQL_ROOT_PASSWORD MYSQL_ROOT_PASSWORD: passwooooorrddd root@controlplane:~#

Correct this by deleting and recreating the mysql pod with the correct environment variable as follows: -

spec: containers:

  • env:
    • name: MYSQL_ROOT_PASSWORD value: paswrd

Also edit the webapp-mysql deployment and make sure that the DB_User environment variable is set to root as follows: -

spec: containers: - env: - name: DB_Host value: mysql-service - name: DB_User value: root - name: DB_Password value: paswrd

Once the objects are recreated, and you should be able to access the application.


* Troubleshooting Test 6: The same 2 tier application is deployed in the zeta namespace. It must display a green web page on success. Click on the App tab at the top of your terminal to view your application. It is currently failed. Troubleshoot and fix the issue.

Stick to the given architecture. Use the same names and port numbers as given in the below architecture diagram. Feel free to edit, delete or recreate objects as necessary.

There are a few things wrong in this setup:

  1. If you inspect the web-service, you will see that the nodePort used is incorrect. This service should be exposed on port 30081 and NOT 30088.

root@controlplane:~# kubectl -n zeta get svc web-service NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE web-service NodePort 10.102.190.212 8080:30088/TCP 3m1s root@controlplane:~#

To correct this, delete the service and recreate it using the below YAML file:

apiVersion: v1 kind: Service metadata: name: web-service namespace: zeta spec: ports:

  • nodePort: 30081 port: 8080 targetPort: 8080 selector: name: webapp-mysql type: NodePort
  1. Also edit the webapp-mysql deployment and make sure that the DB_User environment variable is set to root as follows: -

spec: containers: - env: - name: DB_Host value: mysql-service - name: DB_User value: root - name: DB_Password value: paswrd

  1. The DB_Password used by the mysql pod is incorrect. Delete the current pod and recreate with the correct environment variable as per the snippet below: -

spec: containers:

  • env:
    • name: MYSQL_ROOT_PASSWORD value: paswrd

Once the objects are recreated, and you should be able to access the application. ```

Updated: