MariaDB

We can wrap the Pod from 9.1.2 into a StatefulSet:

kubectl create -f Chapter09/9.2.1_StatefulSet_MariaDB/mariadb-statefulset.yaml

$ kubectl get pvc
NAME                    STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
mariadb-pvc-mariadb-0   Bound    pvc-baaf6655-992e-48f0-8912-cfa28fd70cd8   2Gi        RWO            standard-rwo   7s

This time let’s test it with an ephemeral container running in the cluster, rather than locally via Docker.

kubectl run my -it --rm --restart=Never --pod-running-timeout=3m \
--image mariadb -- mariadb -h mariadb-0.mariadb-service -P 3306 -u root -p

Since it’s in the cluster it may take a moment to spin up, watch in a separate tab

$ kubectl get pod/my -w
NAME   READY   STATUS    RESTARTS   AGE
my     0/1     Pending   0          16s
my     0/1     Pending   0          57s
my     0/1     ContainerCreating   0          57s
my     1/1     Running             0          2m13s

When it’s Running, enter the password and test the DB like before

If you don't see a command prompt, try pressing enter.

It will show this, but don’t press enter (that sends the empty string as a password) instead, type your database password, as configured in the YAML.

If you don't see a command prompt, try pressing enter.

Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 3
Server version: 11.1.2-MariaDB-1:11.1.2+maria~ubu2204 mariadb.org binary distribution

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> CREATE DATABASE foo;
Query OK, 1 row affected (0.002 sec)

MariaDB [(none)]> exit
Bye
pod "my" deleted

The ephemeral Pod is automatically deleted once you exit.

Redis

Another example is Redis. For this one we need to configure a file on the container, which we can do with a ConfigMap

And here’s the Redis StatefulSet that references the ConfigMap

Create both

kubectl create -f Chapter09/9.2.1_StatefulSet_Redis/

Once it’s ready, we can connect via the port-forward plus Docker method, like so:

$ k get pods -w
NAME                          READY   STATUS    RESTARTS   AGE
redis-0                       0/1     Pending   0          12s
redis-0                       0/1     Pending   0          78s
redis-0                       0/1     Pending   0          92s
redis-0                       0/1     ContainerCreating   0          92s
redis-0                       1/1     Running             0          2m8s

$ kubectl port-forward pod/redis-0 6379:637979
Forwarding from 127.0.0.1:6379 -> 6379
Handling connection for 6379

In a separate tab:

$ docker run --net=host -it --rm redis redis-cli
27.0.0.1:6379> INFO
# Server
redis_version:7.2.1
127.0.0.1:6379> exit

Note that Redis is configured with no password, as a purely internal service.

Cleanup

kubectl delete -f Chapter09/9.2.1_StatefulSet_MariaDB
kubectl delete -f Chapter09/9.2.1_StatefulSet_Redis