Exercise

Exercise: Pod¶

Create the votingapp folder on your local machine. Inside this one, create the YAML files containing the Pod specifications for each microservice, following the instructions from the table below:

Microservice	File Name	Pod Name	Container Image
Vote UI	pod-voteui.yaml	vote-ui	voting/vote-ui:latest
Vote	pod-vote.yaml	vote	voting/vote:latest
Redis	pod-redis.yaml	redis	redis:7.0.8-alpine3.17
Worker	pod-worker.yaml	worker	voting/worker:latest
Postgres	pod-db.yaml	db	postgres:15.1-alpine3.17
Result	pod-result.yaml	result	voting/result:latest
Result UI	pod-resultui.yaml	result-ui	voting/result-ui:latest

For the db Pod, make sure to specify an environment variable POSTGRES_PASSWORD with the value postgres.

Deploy the application defined by all of these specifications
What do you notice ?
Delete the application

Tip

The specifications are as follows:

pod-voteui.yamlpod-vote.yamlpod-redis.yamlpod-worker.yamlpod-db.yamlpod-result.yamlpod-resultui.yaml

pod-voteui.yaml

apiVersion: v1
kind: Pod
metadata:
  name: vote-ui
spec:
  containers:
    - image: voting/vote-ui:latest
      name: vote-ui

apiVersion: v1
kind: Pod
metadata:
  name: vote
spec:
  containers:
    - image: voting/vote:latest
      name: vote

apiVersion: v1
kind: Pod
metadata:
  name: redis
spec:
  containers:
    - image: redis:7.0.8-alpine3.17
      name: redis

apiVersion: v1
kind: Pod
metadata:
  name: worker
spec:
  containers:
    - image: voting/worker:latest
      name: worker
      imagePullPolicy: Always

apiVersion: v1
kind: Pod
metadata:
  name: db
spec:
  containers:
  - image: postgres:15.1-alpine3.17
    name: postgres
    env:
      - name: POSTGRES_PASSWORD
        value: postgres

apiVersion: v1
kind: Pod
metadata:
  name: result
spec:
  containers:
    - image: voting/result:latest
      name: result

apiVersion: v1
kind: Pod
metadata:
  name: result-ui
spec:
  containers:
    - image: voting/result-ui:latest
      name: result-ui

The application can be launched with the following command:
```
kubectl apply -f votingapp
```
Info

If a folder is specifed, all the YAML files in that directory are created.

What do you notice ?

Some Pods are in error:

$ kubectl get po
NAME        READY   STATUS             RESTARTS     AGE
db          1/1     Running            0            25s
redis       1/1     Running            0            25s
result      1/1     Running            0            25s
result-ui   0/1     CrashLoopBackOff   1 (4s ago)   24s
vote        1/1     Running            0            25s
vote-ui     0/1     CrashLoopBackOff   1 (3s ago)   25s
worker      1/1     Running            0            25s

If we take the vote-ui Pod as an example, the logs show that it cannot connect to vote:

$ kubectl logs vote-ui  
/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
10-listen-on-ipv6-by-default.sh: info: Getting the checksum of /etc/nginx/conf.d/default.conf
10-listen-on-ipv6-by-default.sh: info: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf
/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh
/docker-entrypoint.sh: Configuration complete; ready for start up
2024/02/08 11:10:20 [emerg] 1#1: host not found in upstream "vote" in /etc/nginx/nginx.conf:44
nginx: [emerg] host not found in upstream "vote" in /etc/nginx/nginx.conf:44

Moreover, the logs from the worker Pod indicate that it cannot connect to the Redis Pod:

$ kubectl logs worker
...
Waiting for Redis dial tcp: lookup redis on 10.96.0.10:53: no such host

The Pods for the different microservices are created, but they cannot communicate with each other because we need to create Services. We will add this in the next step, which will allow us to have a fully functional application.

We delete the application with the following command:
```
kubectl delete -f votingapp
```