Zalando Postgres Operator creates and manages PostgreSQL clusters running in Kubernetes.
It delivers an easy to run highly-available PostgreSQL clusters on Kubernetes powered by proven solutions "under the hood", such as:
This project is my notes doing the Quickstart.
This guide aims to give you a quick look and feel for using the Postgres Operator on a local Kubernetes environment.
Since the Postgres Operator is designed for the Kubernetes (K8s) framework, hence set it up first. For local tests I'm using k3d, which allows creating multi-nodes K8s clusters running on Docker.
To interact with the K8s infrastructure install its CLI runtime kubectl.
This quickstart assumes that you have started minikube or created a local kind cluster.
I created a new cluster using k3d (k3s wrapper).
$ make k8s/cluster/upConfiguring the Postgres Operator is only possible before deploying a new
Postgres cluster. This can work in two ways: via a ConfigMap or a custom
OperatorConfiguration object. More details on configuration can be found
here.
The Postgres Operator can be deployed in the following ways:
- Manual deployment
- Kustomization
- Helm chart
The Postgres Operator can be installed simply by applying yaml manifests. Note,
we provide the /manifests directory as an example only; you should consider
adjusting the manifests to your K8s environment (e.g. namespaces).
# Please execute the script only from the root directory of this repo.
# First, clone the repository and change to the directory
$ git clone https://github.com/zalando/postgres-operator.git pgop
# apply the manifests in the following order
$ kubectl create -f pgop/manifests/configmap.yaml # configuration
configmap/postgres-operator created
$ kubectl create -f pgop/manifests/operator-service-account-rbac.yaml # identity and permissions
serviceaccount/postgres-operator created
clusterrole.rbac.authorization.k8s.io/postgres-operator created
clusterrolebinding.rbac.authorization.k8s.io/postgres-operator created
clusterrole.rbac.authorization.k8s.io/postgres-pod created
$ kubectl create -f pgop/manifests/postgres-operator.yaml # deployment
deployment.apps/postgres-operator created
$ kubectl create -f pgop/manifests/api-service.yaml # operator API to be used by UI
service/postgres-operator createdThere is a Kustomization manifest that combines the mentioned resources (except for the CRD) - it can be used with kubectl 1.14 or newer as easy as:
kubectl apply -k github.com/zalando/postgres-operator/manifests
For convenience, they have automated starting the operator with minikube using
the run_operator_locally script. It applies the
acid-minimal-cluster. manifest.
$ ./pgop/run_operator_locally.sh
Alternatively, the operator can be installed by using the provided Helm chart which saves you the manual steps. Clone this repo and change directory to the repo root. With Helm v3 installed you should be able to run:
$ helm install postgres-operator ./pgop/charts/postgres-operatorSee the quickstart doc for more.
Starting the operator may take a few seconds. Check if the operator pod is running before applying a Postgres cluster manifest.
# if you've created the operator using yaml manifests
$ kubectl get pod -l name=postgres-operator
# if you've created the operator using helm chart
$ kubectl get pod -l app.kubernetes.io/name=postgres-operatorIf the operator doesn't get into Running state, either check the latest K8s
events of the deployment or pod with kubectl describe or inspect the operator
logs:
$ kubectl logs "$(kubectl get pod -l name=postgres-operator --output='name')"In the following paragraphs we describe how to access and manage PostgreSQL clusters from the command line with kubectl. But it can also be done from the browser-based Postgres Operator UI. Before deploying the UI make sure the operator is running and its REST API is reachable through a K8s service. The URL to this API must be configured in the deployment manifest of the UI.
To deploy the UI simply apply all its manifests files or use the UI helm chart:
# manual deployment
$ kubectl apply -f pgop/ui/manifests/
deployment.apps/postgres-operator-ui created
ingress.networking.k8s.io/postgres-operator-ui created
service/postgres-operator-ui created
serviceaccount/postgres-operator-ui created
clusterrole.rbac.authorization.k8s.io/postgres-operator-ui created
clusterrolebinding.rbac.authorization.k8s.io/postgres-operator-ui created
error: unable to recognize "pgop/ui/manifests/kustomization.yaml": no matches for kind "Kustomization" in version "kustomize.config.k8s.io/v1beta1"
# or kustomization
$ kubectl apply -k github.com/zalando/postgres-operator/ui/manifests
# or helm chart
$ helm install postgres-operator-ui ./charts/postgres-operator-uiLike with the operator, check if the UI pod gets into Running state:
# if you've created the operator using yaml manifests
$ kubectl get pod -l name=postgres-operator-ui
# if you've created the operator using helm chart
$ kubectl get pod -l app.kubernetes.io/name=postgres-operator-uiYou can now access the web interface by port forwarding the UI pod (mind the
label selector) and enter localhost:8081 in your browser:
$ kubectl port-forward svc/postgres-operator-ui 8081:80
Forwarding from 127.0.0.1:8081 -> 8081
Forwarding from [::1]:8081 -> 8081
Handling connection for 8081$ curl -i localhost:8081
HTTP/1.1 200 OK
Content-Type: text/html; charset=utf-8
Content-Length: 4699
Date: Fri, 15 Oct 2021 15:10:37 GMT
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>PostgreSQL Operator UI</title>
...
</html>Available option are explained in detail in the UI docs.
If the operator pod is running it listens to new events regarding postgresql
resources. Now, it's time to submit your first Postgres cluster manifest.
# create a Postgres cluster
$ kubectl create -f pgop/manifests/minimal-postgres-manifest.yaml
The postgresql "acid-minimal-cluster" is invalid: spec.postgresql.version: Unsupported value: "14": supported values: "9.3", "9.4", "9.5", "9.6", "10", "11", "12", "13"
# fix and retry
$ kubectl create -f pgop/manifests/minimal-postgres-manifest.yaml
postgresql.acid.zalan.do/acid-minimal-cluster createdAfter the cluster manifest is submitted and passed the validation, the operator
will create Service and Endpoint resources and a StatefulSet which spins up new
Pod(s) given the number of instances specified in the manifest. All resources
are named like the cluster. The database pods can be identified by their number
suffix, starting from -0. They run the
Spilo container image by Zalando. As for the
services and endpoints, there will be one for the master pod and another one for
all the replicas (-repl suffix). Check if all components are coming up. Use
the label application=spilo to filter and list the label spilo-role to see
who is currently the master.
# check the deployed cluster
$ kubectl get postgresql
NAME TEAM VERSION PODS VOLUME CPU-REQUEST MEMORY-REQUEST AGE STATUS
acid-minimal-cluster acid 13 2 1Gi 8m19s Running
# check created database pods
$ kubectl get pods -l application=spilo -L spilo-role
NAME READY STATUS RESTARTS AGE SPILO-ROLE
acid-minimal-cluster-0 1/1 Running 0 21m master
acid-minimal-cluster-1 1/1 Running 0 16m replica
# check created service resources
$ kubectl get svc -l application=spilo -L spilo-role
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SPILO-ROLE
acid-minimal-cluster ClusterIP 10.43.66.169 <none> 5432/TCP 21m master
acid-minimal-cluster-repl ClusterIP 10.43.252.226 <none> 5432/TCP 21m replica
acid-minimal-cluster-config ClusterIP None <none> <none> 17mYou can create a port-forward on a database pod to connect to Postgres. See the user guide for instructions. With minikube it's also easy to retrieve the connections string from the K8s service that is pointing to the master pod:
$ export HOST_PORT=$(minikube service acid-minimal-cluster --url | sed 's,.*/,,')
$ export PGHOST=$(echo $HOST_PORT | cut -d: -f 1)
$ export PGPORT=$(echo $HOST_PORT | cut -d: -f 2)Note: as I'm not using minikube, I follow the instructions mentioned in the user guide (copied here):
With a
port-forwardon one of the database pods (e.g. the master) you can connect to the PostgreSQL database from your machine. Use labels to filter for the master pod of our test cluster.
# get name of master pod of acid-minimal-cluster
$ export PGMASTER=$(kubectl get pods -o jsonpath={.items..metadata.name} -l application=spilo,cluster-name=acid-minimal-cluster,spilo-role=master -n default)
# set up port forward
$ kubectl port-forward $PGMASTER 6432:5432 -n default
Forwarding from 127.0.0.1:6432 -> 5432
Forwarding from [::1]:6432 -> 5432
Handling connection for 6432Sidenote:
Another way to connect from your host to k8s service running in k3s pod. See k3d doc: exposing services.
Open another CLI and connect to the database using e.g. the psql client. When connecting with the
postgresuser read its password from the K8s secret which was generated when creating theacid-minimal-cluster. As non-encrypted connections are rejected by default set the SSL mode torequire:
$ export PGPASSWORD=$(kubectl get secret postgres.acid-minimal-cluster.credentials.postgresql.acid.zalan.do -o 'jsonpath={.data.password}' | base64 -d)
$ export PGSSLMODE=require
$ psql -U postgres -h localhost -p 6432
psql (14.0 (Ubuntu 14.0-1.pgdg20.04+1), server 13.4 (Ubuntu 13.4-4.pgdg18.04+1))
SSL connection (protocol: TLSv1.3, cipher: TLS_AES_256_GCM_SHA384, bits: 256, compression: off)
...
postgres=#Sidenote:
Check the master database replication:
postgres=# select * from pg_stat_replication\x\g\x
Expanded display is on.
-[ RECORD 1 ]----+------------------------------
pid | 2727
usesysid | 16661
usename | standby
application_name | acid-minimal-cluster-1
client_addr | 10.42.0.14
client_hostname |
client_port | 37126
backend_start | 2021-10-16 09:40:29.651345+00
backend_xmin |
state | streaming
sent_lsn | 0/E0017B0
write_lsn | 0/E0017B0
flush_lsn | 0/E0017B0
replay_lsn | 0/E0017B0
write_lag |
flush_lag |
replay_lag |
sync_priority | 0
sync_state | async
reply_time | 2021-10-16 11:11:47.517085+00
Expanded display is off.Check the replica database replication:
postgres=# select * from pg_stat_wal_receiver\x\g\x
Expanded display is on.
-[ RECORD 1 ]---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
pid | 1262
status | streaming
receive_start_lsn | 0/C000000
receive_start_tli | 3
written_lsn | 0/F000110
flushed_lsn | 0/F000110
received_tli | 3
last_msg_send_time | 2021-10-16 11:21:09.534223+00
last_msg_receipt_time | 2021-10-16 11:21:09.534364+00
latest_end_lsn | 0/F000110
latest_end_time | 2021-10-16 11:12:08.207732+00
slot_name | acid_minimal_cluster_1
sender_host | 10.42.0.12
sender_port | 5432
conninfo | user=standby passfile=/run/postgresql/pgpass host=10.42.0.12 port=5432 sslmode=prefer application_name=acid-minimal-cluster-1 gssencmode=prefer channel_binding=prefer
Expanded display is off.See this SO thread for more: https://stackoverflow.com/a/54164409/206570
To delete a Postgres cluster simply delete the postgresql custom resource.
$ kubectl delete postgresql acid-minimal-cluster
postgresql.acid.zalan.do "acid-minimal-cluster" deletedThis should remove the associated StatefulSet, database Pods, Services and Endpoints. The PersistentVolumes are released and the PodDisruptionBudget is deleted. Secrets however are not deleted and backups will remain in place.
When deleting a cluster while it is still starting up or got stuck during that
phase it can happen
that the postgresql resource is deleted leaving orphaned components behind. This
can cause troubles when creating a new Postgres cluster. For a fresh setup you
can delete your local minikube or kind cluster and start again.