using prometheus pod to monitor a golang webapp pod

Question

I have a golang webapp pod running in kubernetes cluster, and I tried to deploy a prometheus pod to monitor the golang webapp pod.

I specified prometheus.io/port: to 2112 in the service.yaml file, which is the port that the golang webapp is listening on, but when I go to the Prometheus dashboard, it says that the 2112 endpoint is down.

I'm following this guide , tried this thread's solution thread , but still getting result saying 2112 endpoint is down.

Below is the my service.yaml and deployment.yaml

apiVersion: v1
kind: Service
metadata:
  name: prometheus-service
  namespace: monitoring
  annotations:
      prometheus.io/scrape: 'true'
      prometheus.io/path: '/metrics'
      prometheus.io/port:   '2112'
spec:
  selector: 
    app: prometheus-server
  type: NodePort  
  ports:
    - port: 8080
      targetPort: 9090 
      nodePort: 30000
---
apiVersion: v1
kind: Service
metadata: 
  namespace: monitoring
  name: goapp
spec:
  type: NodePort
  selector:
    app: golang
  ports:
    - name: main
      protocol: TCP
      port: 80
      targetPort: 2112
      nodePort: 30001






apiVersion: apps/v1
kind: Deployment
metadata:
  name: prometheus-deployment
  namespace: monitoring
  labels:
    app: prometheus-server
spec:
  replicas: 1
  selector:
    matchLabels:
      app: prometheus-server
  template:
    metadata:
      labels:
        app: prometheus-server
    spec:
      containers:
        - name: prometheus
          image: prom/prometheus
          args:
            - "--config.file=/etc/prometheus/prometheus.yml"
            - "--storage.tsdb.path=/prometheus/"
          ports:
            - containerPort: 9090
          volumeMounts:
            - name: prometheus-config-volume
              mountPath: /etc/prometheus/
            - name: prometheus-storage-volume
              mountPath: /prometheus/
      volumes:
        - name: prometheus-config-volume
          configMap:
            defaultMode: 420
            name: prometheus-server-conf
  
        - name: prometheus-storage-volume
          emptyDir: {}
---
apiVersion: apps/v1
kind: Deployment
metadata:
  namespace: monitoring
  name: golang
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: golang
    spec:
      containers:
        - name: gogo
          image: effy77/gogo2
          ports: 
            - containerPort: 2112
  selector:
    matchLabels:
      app: golang

I will try add prometheus.io/port: 2112 to the prometheus deployment part, as I suspect that might be the cause.

Answer 1

I was confused with where to put the annotations,got my clarifications from this thread , I needed to put it under the service's metadata that needs to be scraped by prothemeus. So in my case it needs to be in goapp's metadata.

apiVersion: v1
kind: Service
metadata: 
  namespace: monitoring
  name: goapp
  annotations:
      prometheus.io/scrape: 'true'
      prometheus.io/path: '/metrics'
      prometheus.io/port:   '2112'