Could two cluster IP services be connected in Kubernetes? - kubernetes

Question

The situation is that I want to connect two cluster IP services that are inside a tenant which already has Traefik as NodePort so that any of these two services can be a LoadBalancer because the NodePort is used by Traefik.
The two services I am trying to connect work as follows. The first one, which I called "Master", will receive a post from the client with a text and will call the other service, called "slave", which will add some text ("Hola Patri") to the text sent by the client. The two services are flask services defined by the app.py in the Docker image. You can see the app.py for both images below:
master/app.py
from flask import Flask, request
import requests
app = Flask(__name__)
#app.route("/", methods = ['GET', 'POST'])
def put():
if request.method == 'POST':
text = request.get_data()
r = requests.post("http://slave:5001",data=text)
result = r.text
return result
if __name__ == '__main__':
app.run(host="0.0.0.0", port=5000, debug=True)
slave/app.py
from flask import Flask, request
app = Flask(__name__)
#app.route("/", methods = ['GET', 'POST'])
def put():
if request.method == 'POST':
text = request.get_data()
#text = request.data
texto_final = str(text) + 'Hola Patri'
return texto_final
if __name__ == '__main__':
app.run(host="0.0.0.0", port=5001, debug=True)
The configuration of the deployments and the services are defined in two yamls: master_src.yaml and slave_src.yaml.
master_src.yaml
kind: Namespace
apiVersion: v1
metadata:
name: innovation
labels:
name: innovation
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: master
namespace: innovation
spec:
replicas: 1
selector:
matchLabels:
app: myapp
template:
metadata:
labels:
app: myapp
spec:
securityContext:
runAsUser: 1000
fsGroup: 1000
containers:
- name: master
imagePullPolicy: Always
securityContext:
runAsUser: 1000
runAsNonRoot: true
image: reg-dhc.app.corpintra.net/galiani/innovation:mastertest
ports:
- protocol: TCP
containerPort: 5000
imagePullSecrets:
- name: galiani-innovation-pull-secret
---
apiVersion: v1
kind: Service
metadata:
name: master
namespace: innovation
spec:
ports:
- protocol: TCP
port: 5000
targetPort: 5000
selector:
app: myapp
slave_src.yaml
kind: Namespace
apiVersion: v1
metadata:
name: innovation
labels:
name: innovation
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: slave
namespace: innovation
spec:
replicas: 1
selector:
matchLabels:
app: myapp
template:
metadata:
labels:
app: myapp
spec:
securityContext:
runAsUser: 1000
fsGroup: 1000
containers:
- name: slave
imagePullPolicy: Always
securityContext:
runAsUser: 1000
runAsNonRoot: true
image: reg-dhc.app.corpintra.net/galiani/innovation:slavetest
ports:
- protocol: TCP
containerPort: 5001
imagePullSecrets:
- name: galiani-innovation-pull-secret
---
apiVersion: v1
kind: Service
metadata:
name: slave
namespace: innovation
spec:
selector:
app: myapp
ports:
- protocol: TCP
port: 5001
targetPort: 5001
I have also created a network policy to allow the traffic between the two services. The yaml used to define the network policy is the following.
networkpolicy_src.yaml
kind: NetworkPolicy
apiVersion: extensions/v1beta1
metadata:
name: ingress-to-all
namespace: innovation
spec:
podSelector:
matchLabels:
app: myapp
ingress:
- from:
- podSelector:
matchLabels:
app: myapp
ports:
- port: 5000
protocol: TCP
- port: 5001
protocol: TCP
policyTypes:
- Ingress
The connection between the master service and the slave service is not working. I can access to the master and slave independently. Nevertheless, when I try to make a POST to the master (using curl) and it should connect to the slave, I get the following error:
curl: (52) Empty reply from server
Thank you for your help in advance!
For the new question I have regarding the connection using traefik. Here is the yaml of the trafik ingress:
kind: Ingress
apiVersion: extensions/v1beta1
metadata:
name: ingress-innovation
namespace: innovation
annotations:
traefik.frontend.rule.type: PathPrefixStrip
spec:
rules:
- http:
paths:
- path: /master
backend:
serviceName: master
servicePort: 5000
- path: /slave
backend:
serviceName: slave
servicePort: 5001
I have also corrected the networkpolicy yaml and now it is:
kind: NetworkPolicy
apiVersion: extensions/v1beta1
metadata:
name: master-to-slave
namespace: innovation
spec:
podSelector:
matchLabels:
app: app-slave
ingress:
- ports:
- port: 5000
protocol: TCP
- port: 5001
protocol: TCP
- from:
- namespaceSelector:
matchLabels:
app: app-master
Thanks again for your help!

Answer 1

The problem could be having same label app: myapp for both master and slave. Change the label to app: master for master deployment and service and app: slave for slave deployment and service.