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Binding an Imported app to an In-cluster Operator Managed PostgreSQL Database

Introduction

This scenario illustrates binding an imported application to an in-cluster operated managed PostgreSQL Database.

Note that this example app is configured to operate with OpenShift 4.5 or newer.

Actions to Perform by Users in 2 Roles

In this example there are 2 roles:

  • Cluster Admin - Installs the operators to the cluster
  • Application Developer - Imports a Node.js application, creates a DB instance, creates a request to bind the application and DB (to connect the DB and the application).

Cluster Admin

The cluster admin needs to install 2 operators into the cluster:

  • Service Binding Operator
  • Backing Service Operator

A Backing Service Operator that is "bind-able," in other words a Backing Service Operator that exposes binding information in secrets, config maps, status, and/or spec attributes. The Backing Service Operator may represent a database or other services required by applications. We'll use postgresql-operator to demonstrate a sample use case.

Install the Service Binding Operator

Navigate to the Operators->OperatorHub in the OpenShift console and in the Developer Tools category select the Service Binding Operator operator

Service Binding Operator as shown in OperatorHub

and install the beta version.

This makes the ServiceBinding custom resource available, that the application developer will use later.

Install the DB operator using a CatalogSource

Apply the following CatalogSource:

kubectl apply -f - << EOD
---
apiVersion: operators.coreos.com/v1alpha1
kind: CatalogSource
metadata:
    name: sample-db-operators
    namespace: openshift-marketplace
spec:
    sourceType: grpc
    image: quay.io/redhat-developer/sample-db-operators-olm:v1
    displayName: Sample DB Operators
EOD

Then navigate to the Operators->OperatorHub in the OpenShift console and in the Database category select the PostgreSQL Database operator

PostgreSQL Database Operator as shown in OperatorHub

and install a beta version.

This makes the Database custom resource available, that the application developer will use later.

Application Developer

Create a namespace called service-binding-demo

The application and the DB needs a namespace to live in so let's create one for them:

kubectl create namespace service-binding-demo

Import an application

In this example we will import an arbitrary Node.js application.

In the OpenShift Console switch to the Developer perspective. (Make sure you have selected the service-binding-demo project). Navigate to the +Add page from the menu and then click on the [From Git] button. Fill in the form with the following:

  • Project = service-binding-demo

  • Git Repo URL = https://github.com/pmacik/nodejs-rest-http-crud

  • Builder Image = Node.js

  • Application Name = nodejs-app

  • Name = nodejs-app

  • Select the resource type to generate = Deployment

  • Create a route to the application = checked

and click on the [Create] button.

Notice, that during the import no DB config was mentioned or requested.

When the application is running navigate to its route to verify that it is up. Notice that in the header it says (DB: N/A). That means that the application is not connected to a DB and so it should not work properly. Try the application's UI to add a fruit - it causes an error proving that the DB is not connected.

Create a DB instance for the application

Now we utilize the DB operator that the cluster admin has installed. To create a DB instance just create a Database custom resource in the service-binding-demo namespace called db-demo:

kubectl apply -f - << EOD
---
apiVersion: postgresql.baiju.dev/v1alpha1
kind: Database
metadata:
  name: db-demo
  namespace: service-binding-demo
spec:
  image: docker.io/postgres
  imageName: postgres
  dbName: db-demo
EOD

Express an intent to bind the DB and the application

Now, the only thing that remains is to connect the DB and the application. We let the Service Binding Operator to 'magically' do the connection for us.

Create the following ServiceBinding:

kubectl apply -f - << EOD
---
apiVersion: binding.operators.coreos.com/v1alpha1
kind: ServiceBinding
metadata:
  name: binding-request
  namespace: service-binding-demo
spec:
  bindAsFiles: false
  application:
    name: nodejs-app
    group: apps
    version: v1
    resource: deployments
  services:
  - group: postgresql.baiju.dev
    version: v1alpha1
    kind: Database
    name: db-demo
  mappings:
    - name: DATABASE_DBCONNECTIONIP
      value: "{{ .postgresDB.status.dbConnectionIP }}"
    - name: DATABASE_DBCONNECTIONPORT
      value: "{{ .postgresDB.status.dbConnectionPort }}"
    - name: DATABASE_SECRET_USER
#     value: "{{ .postgresDB.status.dbCredentials.user }}",
      value: "postgres"
    - name: DATABASE_SECRET_PASSWORD
#     value: "{{ .postgresDB.status.dbCredentials.password }}"
      value: "password"
    - name: DATABASE_DBNAME
      value: "{{ .postgresDB.status.dbName }}"
EOD

Note: The issue redhat-developer#982 is opened for tracking user and password evaluation problem. Currently, hard-code user and password as workaround.

  • application - used to search for the application based on the name that we set earlier and the group, version and resource of the application to be a Deployment.
  • services - used to find the backing service - our operator-backed DB instance called db-demo.
  • mappings - used to inject the custom environment variables to application deployment, it's optional.

That causes the application to be re-deployed.

Once the new version is up, go to the application's route to check the UI. In the header you can see (DB: db-demo) which indicates that the application is connected to a DB and its name is db-demo. Now you can try the UI again but now it works!

When the ServiceBinding was created the Service Binding Operator's controller injected the DB connection information into the application's Deployment as environment variables via an intermediate Secret called binding-request， follows as example:

If bindAsFiles: false, the envFrom section will be injected into application deployment
spec:
  template:
    spec:
      containers:
      - envFrom:
        - secretRef:
            name: binding-request-44ddf789

Check the DB connection information as environment variables in application pod:

# env | grep DATA
DATABASE_SECRET_USER=postgres
DATABASE_SECRET_PASSWORD=password
DATABASE_DBNAME=db-demo
DATABASE_USER=postgres
DATABASE_DB.USER=postgres
DATABASE_DB.NAME=db-demo
DATABASE_DB.PORT=5432
DATABASE_DBCONNECTIONPORT=5432
DATABASE_IMAGENAME=postgres
DATABASE_DB.HOST=172.30.58.28
DATABASE_PASSWORD=password
DATABASE_DB.PASSWORD=password
DATABASE_DBCONNECTIONIP=172.30.58.28
DATABASE_IMAGE=docker.io/postgres
If bindAsFiles: true, the volumeMount/volumes sections will be injected into application deployment
spec:
  template:
    spec:
      containers:
      - env:
        volumeMounts:
        - mountPath: /bindings/binding-request
          name: binding-request
      volumes:
      - name: binding-request
        secret:
          defaultMode: 420
          secretName: binding-request-44ddf789

The secret mounted into application pod:

oc get secret binding-request-44ddf789 -o yaml
apiVersion: v1
kind: Secret
metadata:
  name: binding-request-44ddf789
  namespace: service-binding-demo
data:
  DATABASE_DB.HOST: MTcyLjMwLjEzMC4xNTM=
  DATABASE_DB.NAME: ZGItZGVtbw==
  DATABASE_DB.PASSWORD: cGFzc3dvcmQ=
  DATABASE_DB.PORT: NTQzMg==
  DATABASE_DB.USER: cG9zdGdyZXM=
  DATABASE_DBCONNECTIONIP: MTcyLjMwLjEzMC4xNTM=
  DATABASE_DBCONNECTIONPORT: NTQzMg==
  DATABASE_DBNAME: ZGItZGVtbw==
  DATABASE_IMAGE: ZG9ja2VyLmlvL3Bvc3RncmVz
  DATABASE_IMAGENAME: cG9zdGdyZXM=
  DATABASE_PASSWORD: cGFzc3dvcmQ=
  DATABASE_SECRET_PASSWORD: cGFzc3dvcmQ=
  DATABASE_SECRET_USER: cG9zdGdyZXM=
  DATABASE_USER: cG9zdGdyZXM=
type: Opaque

Check the DB connection information as files in application pod:

oc exec -it nodejs-app-869bb569d-cvwqw bash
bash-4.2$ cd bindings/binding-request
bash-4.2$ ls
DATABASE_DBCONNECTIONIP DATABASE_DBCONNECTIONPORT DATABASE_DBNAME  DATABASE_SECRET_PASSWORD DATABASE_SECRET_USER  
db.host  db.name  db.password  db.port  db.user  dbConnectionIP  dbConnectionPort  dbName  image  imageName  password  user
bash-4.2$ cat DATABASE_DBCONNECTIONIP; echo
172.30.58.28
bash-4.2$ cat DATABASE_DBCONNECTIONPORT; echo
5432
bash-4.2$ cat db.user; echo
postgres
bash-4.2$ cat db.password; echo
password

Check the status of Service Binding

ServiceBinding Status depicts the status of the Service Binding operator. More info: https://github.com/kubernetes/community/blob/master/contributors/devel/sig-architecture/api-conventions.md#spec-and-status

To check the status of Service Binding, run the command:

kubectl get servicebinding binding-request -n service-binding-demo -o yaml

Status of Service Binding on successful binding:

status:
  conditions:
  - lastHeartbeatTime: "2020-10-15T13:23:36Z"
    lastTransitionTime: "2020-10-15T13:23:23Z"
    status: "True"
    type: CollectionReady
  - lastHeartbeatTime: "2020-10-15T13:23:36Z"
    lastTransitionTime: "2020-10-15T13:23:23Z"
    status: "True"
    type: InjectionReady
  secret: binding-request-72ddc0c540ab3a290e138726940591debf14c581

where

  • Conditions represent the latest available observations of Service Binding's state
  • Secret represents the name of the secret created by the Service Binding Operator

Conditions have two types CollectionReady and InjectionReady

where

  • CollectionReady type represents collection of secret from the service
  • InjectionReady type represents an injection of the secret into the application

Conditions can have the following type, status and reason:

Type Status Reason Type Status Reason
CollectionReady False EmptyServiceSelector InjectionReady False
CollectionReady False ServiceNotFound InjectionReady False
CollectionReady True InjectionReady False EmptyApplicationSelector
CollectionReady True InjectionReady False ApplicationNotFound
CollectionReady True InjectionReady True

That's it, folks!