How do I know which pod processes the request? - azure

Question

I used this Deployment.yml to create pods.
apiVersion: apps/v1
kind: Deployment
metadata:
name: price-calculation-deployment
labels:
app: price-calculation
spec:
replicas: 2
selector:
matchLabels:
app: price-calculation
template:
metadata:
labels:
app: price-calculation
spec:
containers:
- name: price-calculation
image: ${somewhere}/price-calculation:latest
ports:
- containerPort: 80
protocol: TCP
- name: pc-mongodb
image: mongo:latest
ports:
- containerPort: 27017
protocol: TCP
imagePullSecrets:
- name: acr-auth
And, later on, I used this Service.yml to expose port to external.
apiVersion: v1
kind: Service
metadata:
name: price-calculation-service
spec:
type: LoadBalancer
ports:
- port: 5004
targetPort: 80
protocol: TCP
selector:
app: price-calculation
Finally, both are working now. Good.
As I configured the LoadBalancer in the Service.yml, there shall be a LoadBalancer dispatches requests to the 2 replicas/pods.
Now, I want to know which pod takes the request and how do I know
that?
Thanks!!!

Answer 1

well, the easiest way - make pods write their identity in the response, that way you will know which pod responds. Another way - implement distributed tracing with Zipkin\Jaeger. That will give you deep insights into networking flows.
I believe kubernetes doesnt offer any sort of built-in network tracing.

Answer 2

Append pod name to the response that gets rendered on the user's browser. That is how you know which pod is processing the request

Answer 3

You may view pod logs to see the requests made to the pod:
kubectl logs my-pod # dump pod logs (stdout)
kubectl logs my-pod -c my-container # dump pod container logs (stdout, multi-container case)
Or add to the response in the application itself, for instance in Nodejs app it might look like this:
const http = require('http');
const os = require('os');
var handler = function(request, response) {
response.writeHead(200);
response.end("You have hit " + os.hostname() + "\n");
};
var app = http.createServer(handler);
app.listen(8080);
Then you can use curl to test out your service and get a response:
Request:
curl http://serviceIp:servicePort
Response:
You have hit podName
Depending on the app’s programming language, just find a module/library that provides a utility method to get a hostname and you’ll be good to go to give it back in the response for debugging purposes.