How do pods communicates with the other pod in a cluster created using Kubernetes

Question

I have created 1 master node and 1 worker node with 2 pods using kops in aws. In one pod i have my oracle database running and in other pod i have deployed my java web application. Now to run the java web application needs to talk to the database pod for To communicate between 2 pods in a cluster, i have configured the pod's IP address in my java application. I am able to access the application using the cloud providers public URL, everything is good in the dev environment. But in case of production environment, i cannot keep configuring the database Pod's IP address in my java application Pod.

How do people solve this issue ? Do you guys use Pod's Ip address to communicate with other pod's in kubernetes ? or is there any other way for communication between pods ?

Here is how my Pods look like in the cloud

   NAME                           READY     STATUS    RESTARTS   AGE       IP            NODE
csapp-8cd5d44556-7725f         1/1       Running   2          1d        100.96.1.54   ip-172-56-35-213.us-west-2.compute.internal
csdb-739d459467-92cmh          1/1       Running   0          1h        100.96.1.57   ip-172-27-86-213.us-west-2.compute.internal

Any help or directions on this issue would be helpful.

Answer 1

To make communication between two pods, you should use service resource with port type ClusterPort since they are in the same cluster.

According to the output of kubectl get pods , you have two tiers:

• App Tier: csapp-8cd5d44556-7725f

• Data Tier : csdb-739d459467-92cmh

Below is an example of service resource for data tier, then how it is used inside App tier.

apiVersion: v1
kind: Service
metadata:
  name: example-data-tier
spec:
  selector:
    app: csdb # ⚠️Make sure of this, it should select the POD csdb-...
  ports:
    - name: redis
      protocol: TCP
      port: 6379
      # type (default is ClusterPort which is for internal)

And in the POD of App tier, you should feed the environment variable with values from the service above:

apiVersion: v1
kind: Pod
spec:
  containers:
    - name: xx
      image: "xxx:v1"
      ports:
        - containerPort: 8080
          protocol: TCP
      env:
        - name: "REDIS_URL"
          value: "redis://$(EXAMPLE_DATA_TIER_SERVICE_HOST):$(EXAMPLE_DATA_TIER_SERVICE_PORT_REDIS)"

If your DB is something other than Redis, you need to consider that when applying this solution.