brew install minikube

$brew install minikube

minikube start --vm=true

$minikube start --vm=true

kubectl create namespace postgres

kubectl config set-context postgres --namespace postgres --cluster minikube --user minikube

kubectl config use-context postgres

$kubectl create namespace postgres

$kubectl config set-context postgres --namespace postgres --cluster minikube --user minikube

$kubectl config use-context postgres

There are two ways to create Persistent Volumes. Either you manually create a volume per replica of PostgreSQL or you configure[dynamic provisioning](https://minikube.sigs.k8s.io/docs/handbook/persistent_volumes/#dynamic-provisioning-and-csi). For simplicity we choose the manual approach first.

kubectl apply -f pv-0.yaml

kubectl apply -f pv-1.yaml

kubectl apply -f pv-2.yaml

$kubectl apply -f pv-0.yaml

$kubectl apply -f pv-1.yaml

$kubectl apply -f pv-2.yaml

kubectl get pv

$kubectl get pv

NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE

pv-postgresql-0 1Gi RWO Retain Available default 9s

pv-postgresql-1 1Gi RWO Retain Available default 7s

A[Headless Service](https://kubernetes.io/docs/concepts/services-networking/service/#headless-services) is specified with`clusterIP: None` and omits to use a L4 load balancer. By also defining a selector, the endpoints controller creates`Endpoint` records and also modifies the DNS configuration so that`A` records are returned that point directly to the pods.

kubectl apply -f svc.yaml

$kubectl apply -f svc.yaml

kubectl describe svc postgresql-svc

$kubectl describe svc postgresql-svc

Name: postgresql-svc

Namespace: postgres

Labels: sfs=postgresql-sfs

PostgreSQL uses environment variables for configuration. The most important one for the official[PostgreSQL Docker image](https://hub.docker.com/_/postgres) is`POSTGRES_PASSWORD`. We utilize[Secrets](https://kubernetes.io/docs/concepts/configuration/secret/) to inject the respective value into the container later on.

kubectl create secret generic postgresql-secrets --from-literal=POSTGRES_PASSWORD=tes6Aev8

$kubectl create secret generic postgresql-secrets --from-literal=POSTGRES_PASSWORD=tes6Aev8

kubectl describe secrets postgresql-secrets

$kubectl describe secrets postgresql-secrets

Name: postgresql-secrets

Namespace: postgres

Labels:<none>

A[Stateful Set](https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/) is similar to a_Replica Set_ in a sense that it also handles pods for the configured number of replicas. In contrast to a_Replica Set_, it maintains a sticky identity for each of them. This means they are created in a fixed, sequential order and deleted counterwise. Their network identity is stable as well, what enables us to reference them by the automatically assigned DNS host inside of the cluster.

kubectl apply -f sfs.yaml

$kubectl apply -f sfs.yaml

kubectl get statefulsets

$kubectl get statefulsets

NAME READY AGE

postgresql-sfs 3/3 16s

kubectl get pods

$kubectl get pods

NAME READY STATUS RESTARTS AGE

postgresql-sfs-0 1/1 Running 0 86s

postgresql-sfs-1 1/1 Running 0 83s

postgresql-sfs-2 1/1 Running 0 80s

kubectl logs postgresql-sfs-0

$kubectl logs postgresql-sfs-0

PostgreSQL Database directory appears to contain a database; Skipping initialization

2021-08-04 08:19:50.838 UTC [26] LOG: database system was shut down at 2021-08-03 14:33:17 UTC

2021-08-04 08:19:50.843 UTC [1] LOG: database system is ready to accept connections

kubectl describe svc postgresql-svc

$kubectl describe svc postgresql-svc

Name: postgresql-svc

Namespace: postgres

Labels: sfs=postgresql-sfs

You are able to directly connect to PostgreSQL by starting`bash` within a particular pod.

kubectlexec -it postgresql-sfs-0 -- bash

$kubectlexec -it postgresql-sfs-0 -- bash

root@postgresql-sfs-0:/# PGPASSWORD=tes6Aev8 psql -U postgres

psql (13.3 (Debian 13.3-1.pgdg100+1))

Type"help"for help.

An alternative approach is running a temporary PostgreSQL container and using the included`psql` to connect to one of the database instances. Where the hostname is the automatically created DNS host of the service we deployed earlier. The format of that hostname is:`<service-name>.<namespace>.svc.cluster.local` and will be resolved to a random pod running a database server.

kubectl run -it --rm pg-psql --image=postgres:13.3 --restart=Never --env="PGPASSWORD=tes6Aev8" -- psql -h postgresql-svc.postgres.svc.cluster.local -U postgres

$ kubectl run -it --rm pg-psql --image=postgres:13.3 --restart=Never \

--env="PGPASSWORD=tes6Aev8" -- \

psql -h postgresql-svc.postgres.svc.cluster.local -U postgres

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

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

/# ping postgresql-svc.postgres.svc.cluster.local

PING postgresql-svc.postgres.svc.cluster.local (172.17.0.3): 56 data bytes