postgres-operator-tutorial

requirements

• kind - 0.11.0
• docker - 20.10.7
• psql

init zalando-operator submodules from official repository

git submodule init

setup k8s cluster on localhost

During this tutorial we will be using kind to provision k8s cluster on docker, with following configuration:

• 1 master node
• 3 worker nodes

verify if any cluster is available

kind get clusters

create k8s cluster

kind create cluster --config manifests/kind/cluster.yml

verify if kubectl context is switched to proper cluster

$ kubectl get nodes                                            
NAME                 STATUS   ROLES                  AGE   VERSION
kind-control-plane   Ready    control-plane,master   54s   v1.21.1
kind-worker          Ready    <none>                 25s   v1.21.1
kind-worker2         Ready    <none>                 25s   v1.21.1
kind-worker3         Ready    <none>                 25s   v1.21.1

setup zalando-operator

provision PostgreSQL operator

cd postgres-operator
kubectl create -f manifests/configmap.yaml
kubectl create -f manifests/operator-service-account-rbac.yaml
kubectl create -f manifests/postgres-operator.yaml
kubectl create -f manifests/api-service.yaml 

check if operator is running

kubectl get pod -l name=postgres-operator
NAME                                 READY   STATUS    RESTARTS   AGE
postgres-operator-55b8549cff-84gp7   1/1     Running   0          118s

deploy the oparator UI

kubectl apply -f postgres-operator/ui/manifests/

verify if its running

kubectl get pod -l name=postgres-operator-ui

port-forward the operator UI service to localhost

kubectl port-forward svc/postgres-operator-ui 8081:80

then go to http://localhost:8081 and explore

deploy first PostgreSQL cluster

kubectl apply -f manifests/postgres-12-cluster.yml

connect to PostgreSQL master

port-forward the master node to localhost

export PGPASSWORD=$(kubectl get secret postgres.acid-first.credentials -o 'jsonpath={.data.password}' | base64 -d)

export PGMASTER=$(kubectl get pods -o jsonpath={.items..metadata.name} -l application=spilo,cluster-name=acid-first,spilo-role=master -n default)

kubectl port-forward $PGMASTER 6432:5432 -n default

connect to master instance

$ psql -U postgres -h localhost -p 6432
psql (12.7 (Ubuntu 12.7-0ubuntu0.20.04.1))
SSL connection (protocol: TLSv1.3, cipher: TLS_AES_256_GCM_SHA384, bits: 256, compression: off)
Type "help" for help.

verify the instance version

SELECT version();

cerate sample table within new database

CREATE DATABASE ssu_operator_labs; 

#connect to created database
\c ssu_operator_labs 

CREATE TABLE ssu_tab (random_str text);

#list all tables that matches following regex
\dt ssu*

seed sample database with data

# seed the values
INSERT INTO ssu_tab (random_str) VALUES ('Magiera'), ('Dygas'), ('Bodera');

SELECT * FROM ssu_tab;

 random_str 
------------
 Magiera
 Dygas
 Bodera
(3 rows)

verify if the data was replicated to the slave cluster

kubectl port-forward acid-first-1 6433:5432 -n default

and then inspect the values

\c ssu_operator_labs 
SELECT * FROM ssu_tab;

upgrade an existing PostgreSQL cluster version

open another terminal session and watch pods status

kubectl get pods  -w 

change the spec.postgresql.version from 12 to 13 in postgres/v12-cluster.yml (example in postgres/v13-cluster.yml) and apply edited config:

kubectl apply -f manifests/postgres-13-cluster.yml 

and wait till all pods will be in running state again

then verify the version on master node

SELECT version();

failover

in this example we will try If our setup if capable of handling failover

get the current master name

$ kubectl get pods -o jsonpath={.items..metadata.name} -l application=spilo,cluster-name=acid-first,spilo-role=master -n default
acid-first-2

delete the master instance

$ kubectl delete pod acid-first-2 
pod "acid-first-2" deleted

check if new master will be elected

$ kubectl get pods -o jsonpath={.items..metadata.name} -l application=spilo,cluster-name=acid-first,spilo-role=master -n default
acid-first-0

then check which one will be switched to readonly mode and if current master is writeable