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How to create a new PostgreSQL cluster

Create a manifest for a new PostgreSQL cluster

As an example you can take this minimal example:

apiVersion: "acid.zalan.do/v1"
kind: postgresql
metadata:
  name: acid-minimal-cluster
spec:
  teamId: "ACID"
  volume:
    size: 1Gi
  numberOfInstances: 2
  users:
    # database owner
    zalando:
    - superuser
    - createdb

    # role for application foo
    foo_user:

  #databases: name->owner
  databases:
    foo: zalando
  postgresql:
    version: "10"

Create a new Spilo cluster

$ kubectl create -f manifests/minimal-postgres-manifest.yaml

Watch pods being created

$ kubectl get pods -w --show-labels

Connect to PostgreSQL

We can use the generated secret of the postgres robot user to connect to our acid-minimal-cluster master running in Minikube:

$ export PGHOST=db_host
$ export PGPORT=db_port
$ export PGPASSWORD=$(kubectl get secret postgres.acid-minimal-cluster.credentials -o 'jsonpath={.data.password}' | base64 -d)
$ psql -U postgres

Defining database roles in the operator

Postgres operator allows defining roles to be created in the resulting database cluster. It covers three use-cases:

create application roles specific to the cluster described in the manifest: manifest roles.
create application roles that should be automatically created on every cluster managed by the operator: infrastructure roles.
automatically create users for every member of the team owning the database cluster: teams API roles.

In the next sections, we will cover those use cases in more details.

Manifest roles

Manifest roles are defined directly in the cluster manifest. See minimal postgres manifest for an example of zalando role, defined with superuser and createdb flags.

Manifest roles are defined as a dictionary, with a role name as a key and a list of role options as a value. For a role without any options supply an empty list.

The operator accepts the following options: superuser, inherit, login, nologin, createrole, createdb, replication, bypassrls.

By default, manifest roles are login roles (aka users), unless nologin is specified explicitly.

The operator automatically generates a password for each manifest role and places it in the secret named {username}.{team}-{clustername}.credentials.postgresql.acid.zalan.do in the same namespace as the cluster. This way, the application running in the Kubernetes cluster and working with the database can obtain the password right from the secret, without ever sharing it outside of the cluster.

At the moment it is not possible to define membership of the manifest role in other roles.

Infrastructure roles

An infrastructure role is a role that should be present on every PostgreSQL cluster managed by the operator. An example of such a role is a monitoring user. There are two ways to define them:

Exclusively via the infrastructure roles secret (specified by the infrastructure_roles_secret_name parameter).

The role definition looks like this (values are base64 encoded):

    user1: ZGJ1c2Vy
    password1: c2VjcmV0
    inrole1: b3BlcmF0b3I=

A block above describes the infrastructure role 'dbuser' with the password 'secret' that is the member of the 'operator' role. For the following definitions one must increase the index, i.e. the next role will be defined as 'user2' and so on. Note that there is no way to specify role options (like superuser or nologin) this way, and the resulting role will automatically be a login role.

Via both the infrastructure roles secret and the infrastructure role configmap (with the same name as the infrastructure roles secret).

The infrastructure roles secret should contain an entry with 'rolename: rolepassword' for each role, and the role description should be specified in the configmap. Below is the example:

    dbuser: c2VjcmV0

and the configmap definition for that user:

    data:
      dbuser: |
        inrole: [operator, admin]  # following roles will be assigned to the new user
        user_flags:
          - createdb
        db_parameters:  # db parameters, applied for this particular user
          log_statement: all

Note that the definition above allows for more details than the one that relies solely on the infrastructure role secret. In particular, one can allow membership in multiple roles via the inrole array parameter, define role flags via the user_flags list and supply per-role options through the db_parameters dictionary. All those parameters are optional.

The definitions that solely use the infrastructure roles secret are more limited and considered legacy ones; one should use the new style that specifies infrastructure roles using both the secret and the configmap. You can mix both in the infrastructure role secret, as long as your new-style definition can be clearly distinguished from the old-style one (for instance, do not name new-style rolesuserN).

Since an infrastructure role is created uniformly on all clusters managed by the operator, it makes no sense to define it without the password. Such definitions will be ignored with a prior warning.

See infrastructure roles secret and infrastructure roles configmap for the examples.

Use taints and tolerations for dedicated PostgreSQL nodes

To ensure Postgres pods are running on nodes without any other application pods, you can use taints and tolerations and configure the required toleration in the manifest.

apiVersion: "acid.zalan.do/v1"
kind: postgresql
metadata:
  name: acid-minimal-cluster
spec:
  teamId: "ACID"
  tolerations:
  - key: postgres
    operator: Exists
    effect: NoSchedule

How to clone an existing PostgreSQL cluster

To spin up a new cluster as a clone of the existing one, you need to provide a clone section in the spec:

apiVersion: "acid.zalan.do/v1"
kind: postgresql

metadata:
  name: acid-test-cluster
spec:
  clone:
    uid: "efd12e58-5786-11e8-b5a7-06148230260c"
    cluster: "acid-batman"
    timestamp: "2017-12-19T12:40:33+01:00"

Here cluster is a name of a target cluster that is going to be cloned. If timestamp is not empty, then a new cluster will be cloned from an S3 bucket, that was created by operator, using the latest backup before the timestamp. In this case uid field is also mandatory - operator will use it to find an S3 bucket. You can find this field from metadata of a target cluster:

apiVersion: acid.zalan.do/v1
kind: postgresql
metadata:
  name: acid-test-cluster
  uid: efd12e58-5786-11e8-b5a7-06148230260c

If timestamp is empty or absent, a new cluster will be cloned from an existing alive cluster using pg_basebackup. Note that timezone required for timestamp (offset relative to UTC, see RFC 3339 section 5.6)

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