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Kubernetes database controller

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This is a database controller for Kubernetes. It allows users to provision on-demand databases for their applications by creating "Database" resources in Kubernetes, without requiring access to the database server. This is useful for staging sites, CI builds, review apps and other situations where new databases need to be provisioned frequently.

The controller works by watching for creation of a new custom resouce type called Database, and running CREATE USER / CREATE DATABASE statements on the configured database server(s). Both MySQL and PostgreSQL databases are supported, and multiple database classes can be configured for each type (e.g. "staging" and "review"). When the Database resource is deleted in Kubernetes, the corresponding database and user are dropped.

WARNING: This is experimental software and drops databases by design. We strongly recommend keeping regular backups, and not running it on production databases.

Cluster setup

For the provisioner to work, you must create the Database custom resource type on your Kubernetes cluster:

$ kubectl apply -f https://raw.githubusercontent.com/kubejam/database-controller/master/crd.yaml

(For Kubernetes 1.6 or earlier, use tpr.yaml instead; this creates a ThirdPartyResource which you will need to migrate when upgrading to 1.8 or later.)

In addition, if your cluster uses authorization (e.g. RBAC) you should give users permission to create and delete Database resources in the kubejam/v1 API group.

Installation

The easiest way to run the provisioner is as a pod inside Kubernetes. See the example deployment.yaml for an example. A configuration file is required; an example is provided in config.yaml.example.

Create the configuration in config.yaml and apply it to the cluster:

$ kubectl create namespace database-controller
$ kubectl -n database-controller create secret generic config --from-file=config.yaml=config.yaml

Then deploy the controller:

$ kubectl apply -f https://raw.githubusercontent.com/kubejam/database-controller/master/deployment.yaml

Usage

To provision a database, create a Database resource that looks like this:

apiVersion: kubejam/v1
kind: Database
metadata:
  namespace: default
  name: mydb
spec:
  type: postgresql
  class: default
  secretName: mydb-secret

type is the type of database to create; currently, postgresql and mysql are the supported types. class is the class of database to create. If not specified, the default is default. The specified class must be configured in config.yaml, or provisioning will fail.

secretName is the name of a secret that will be created to store the database URL. The created secret will look like this:

apiVersion: v1
kind: Secret
metadata:
  namespace: default
  name: mydb-secret
type: Opaque
data:
  database-url: cG9zdGdyZXNxbDovL2RlZmF1bHRfbXlkYjplOFFFTGZUWkpkdW0wVHJVQHBvc3RncmVzLmRhdGFiYXNlLnN2Yy9kZWZhdWx0X215ZGI=
$ echo 'cG9zdGdyZXNxbDovL2RlZmF1bHRfbXlkYjplOFFFTGZUWkpkdW0wVHJVQHBvc3RncmVzLmRhdGFiYXNlLnN2Yy9kZWZhdWx0X215ZGI=' | base64 -d
postgresql://default_mydb:e8QELfTZJdum0TrU@postgres.database.svc/default_mydb

To delete a provisioned database, delete the Database resource:

$ kubectl delete database mydb

Notes / bugs

Compared to the persistent volume provisioner, this controller is very primitive.

It does not use finalizers to ensure consistent database deletion, so it's possible for a Database record to be deleted while the corresponding database isn't dropped, if an error occurs or the controller misses the deletion event.

It does not use a lease to serialize operations, so only one copy can be running at once.

There is no permission checking on the created Secret, so a user with access to create Database resources in a namespace can overwrite existing Secrets in that namespace. (This is not considered a serious problem since Kubernetes access control is usually done on the namespace level anyway.)