connect Postgres database in docker to app in Kubernetes - postgresql

Question

I'm new with Kubernetes and I try to understand how to connect Postgres database which is outside from Kubernetes (exactly in docker with ip address 172.17.0.2 and port 5432) to my webapp in Kubernetes.
I try connect database through env variable PS_DATABASE_URL in Deployment section.
But it cannot find mentioned url for postgres. How it need to be done correctly?
webapp.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: webapp-deployment
labels:
app: webapp
spec:
replicas: 1
selector:
matchLabels:
app: webapp
template:
metadata:
labels:
app: webapp
spec:
containers:
- name: webapp
image: dmitriy83/flask_kuber
ports:
- containerPort: 5000
env:
- name: PS_DATABASE_URL
value: postgresql://postgres:password#172.17.0.2:5432/db
---
apiVersion: v1
kind: Service
metadata:
name: webapp-service
spec:
type: NodePort
selector:
app: webapp
ports:
- protocol: TCP
port: 5000
targetPort: 5000
nodePort: 30100

Answer 1

I figured it out. it depends from cloud provider. For this example i use amazon cloud and to connect database on amazon (this is external service). So we must define it in yaml file like an external service.
postgres_external.yaml
kind: Service
apiVersion: v1
metadata:
name: postgres
spec:
type: ExternalName
externalName: db.cdmhjidhpqyu.us-east-2.rds.amazonaws.com
to connect to external service you need to link to it on deployment.
webapp.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: webapp-deployment
labels:
app: webapp
spec:
replicas: 1
selector:
matchLabels:
app: webapp
template:
metadata:
labels:
app: webapp
spec:
containers:
- name: webapp
image: dmitriy83/flask_kuber
ports:
- containerPort: 5000
env:
- name: PS_DATABASE_URL
value: postgresql://<username>:<password>#postgres:5432/db
---
apiVersion: v1
kind: Service
metadata:
name: webapp-service
spec:
type: NodePort
selector:
app: webapp
ports:
- protocol: TCP
port: 5000
targetPort: 5000
nodePort: 30100
Please note in webapp.yaml, env section value value: postgresql://<username>:<password>#postgres:5432/db   contains postgres - this is name of our external service which we define in postgres_external.yaml