I am wondering what to specify in a separate deployment in order to have it access a DB deployment/service. Here is the DB deployment/service:
apiVersion: v1
kind: Service
metadata:
name: oracle-db
labels:
app: oracle-db
spec:
ports:
- name: oracle-db
port: 1521
protocol: TCP
targetPort: 1521
selector:
app: oracle-db
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: oracle-db-depl
labels:
app: oracle-db
spec:
selector:
matchLabels:
app: oracle-db
replicas: 1
strategy:
type: Recreate
template:
metadata:
labels:
app: oracle-db
spec:
containers:
- name: oracle-db
image: oracledb:latest
imagePullPolicy: Always
ports:
- containerPort: 1521
env:
...How exactly do I specify the connection in the separate deployment? Do I specify the oracle-db service name somewhere? So far I specify a containerPort in the container.
If the other app deployment is in the same namespace you can refer to the oracle service by oracle-db. Here is an example of a word-press application using oracle.
apiVersion: apps/v1
kind: Deployment
metadata:
name: wordpress
labels:
app: wordpress
spec:
selector:
matchLabels:
app: wordpress
tier: frontend
strategy:
type: Recreate
template:
metadata:
labels:
app: wordpress
tier: frontend
spec:
containers:
- image: wordpress:4.8-apache
name: wordpress
env:
- name: WORDPRESS_DB_HOST
value: oracle-db
ports:
- containerPort: 80
name: wordpressAs you can see oracle service is being referred by oracle-db as an environment variable.
If the service is in different namespace than the app deployment then you can refer to it as oracle-db.namespacename.svc.cluster.local
https://kubernetes.io/docs/tutorials/stateful-application/mysql-wordpress-persistent-volume/
Services in Kubernetes are an "abstract way to expose an application running on a set of Pods as a network service." (k8s documentation)
You can access your pod by its IP and port that Kubernetes have given to it, but that's not a good practice as the Pods can die and another one will be created (if controlled by a Deployment/ReplicaSet). When the new one is created, a new IP will be used, and everything on your app will start to fail.
To solve this you can expose your Pod using a Service (as you already have done), and use service-name:service-port assigned to the Service to access your Pod. In this case, even if the Pod dies and a new one is created, Kubernetes will keep forwarding the traffic to the right Pod.