I am learning Kubernetes, and have great trouble understanding the use of names/labels/selectors, and whether pod names and container names should be aligned.

I have a setup with a .NET Core MVC App, a PostgreSQL database and an Nginx reverse proxy.

It is working great with this docker-compose.yml:

version: "3.7"

services:

  reverseproxy:
    build:
      context: ./Nginx
      dockerfile: ../Nginx.dockerfile
    ports:
      - "80:80"
      - "443:443"
    restart: always

  db:
    image: postgres:12.1-alpine
    environment:
      POSTGRES_PASSWORD: "mvcdbsecretpassword"

  mvc:
    depends_on:
      - reverseproxy
      - db
    build:
      context: .
      dockerfile: ./MyMvc.dockerfile
    environment:
      ConnectionStrings.MyMvc: "Host=db;Port=5432;Database=MyMvcDb;Username=postgres;Password=mvcdbsecretpassword"
    expose:
      - "5000"
    restart: always

The MVC app container is built and tagged and pushed to my Docker hub registry. At startup it logs the connection string and it accepts the settings from the docker-compose file (obviously - it is working after all).

I have converted this into six kubernetes yaml files:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: postgres
  labels:
    name: postgres
spec:
  replicas: 1
  selector:
    matchLabels:
      app: postgres
  template:
    metadata:
      labels:
        app: postgres
    spec:
      containers:
      - name: postgres
        image: postgres:12.1-alpine
        env:
        - name: POSTGRES_PASSWORD
          value: mvcdbsecretpassword
      restartPolicy: Always
---
apiVersion: v1
kind: Service
metadata:
  name: postgres
  labels:
    app: postgres
spec:
  ports:
  - name: "postgres"
    port: 5432
    targetPort: 5432
  selector:
    app: postgres
  type: ClusterIP
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: mvc
  labels:
    name: mymvc
spec:
  replicas: 1
  selector:
    matchLabels:
      app: mymvc
  template:
    metadata:
      labels:
        app: mymvc
    spec:
      containers:
      - name: mvc
        image: mymvc:v2
        env:
          - name: ConnectionStrings.MyMvc
            value: "Host=postgres;Port=5432;Database=MyMvcDb;Username=postgres;Password=mvcdbsecretpassword"
      restartPolicy: Always
---
apiVersion: v1
kind: Service
metadata:
  name: mvc
  labels:
    app: mymvc
spec:
  ports:
  - name: "mvc"
    port: 5000
    targetPort: 5000
  selector:
    app: mymvc
  type: ClusterIP
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: reverseproxy-deployment
  labels:
    app: mymvc
spec:
  replicas: 1
  selector:
    matchLabels:
      app: mymvc
  template:
    metadata:
      labels:
        app: mymvc
    spec:
      containers:
      - name: reverseproxy
        image: reverseproxy:v2
        ports:
        - containerPort: 80
        - containerPort: 443
---
apiVersion: v1
kind: Service
metadata:
  name: reverseproxy-service
  labels:
    app: mymvc
spec:
  ports:
  - name: "http"
    port: 80
    targetPort: 80
  - name: "https"
    port: 443
    targetPort: 443
  selector:
    app: mymvc
  type: LoadBalancer

As stated earlier I am very confused about when to use names and when to use labels.

A little guidance will be greatly appreciated.

EDIT: David Maze helped me understand the relationship between names, labels, and selectors. YAML files are updated accordingly.

I also added a service for the mvc app exposing port 5000.

Now the pods are no longer crashing, but I still have no access to the MVC app.

I guess, I should mention that I'm trying to make this run on Docker Desktop on a Windows 10 box.

The reverse proxy made sense in the Compose stack, but I am no longer sure, that it also makes sense in a Kubernetes Cluster, or if I should rather setup some kind of Ingress controller.

Could someone tell me, if it is even possible to test this setup on Docker Desktop?

Running kubectl get nodes -o wide reveals that there is no external IP, but I'm also not sure if the cluster is mirrored to localhost.