Error: Connection refused while connecting to upstream

Questions
1

I have set up a docker-compose yaml file to launch Kong Gateway, and to have it point to my backend.
The docker compose file starts up just fine with Kong and my API service. I can verify that kong is up and running as I can query it’s services etc…

The thing is I’m using a yaml configuration file to setup my services and routes:

_format_version: "2.1"
_transform: true
services:
  - name: registrations-api-gateway
    url: http://127.0.0.1:4556
#   # Entities can store tags as metadata
    tags:
    - example_1
    - example_2
    - example_3
    - example_4
    routes:
    - name: reg-route
      methods:
      - POST
      paths:
      - /registrations

My docker-compose file looks like this:

  kong:
    image: kong:latest
    user: root
    volumes:
      - ./src/kong/:/root/kong/
    environment:
      KONG_DATABASE: "off"
      KONG_DECLARATIVE_CONFIG: "/root/kong/kong.yml"
      KONG_PROXY_ACCESS_LOG: /dev/stdout
      KONG_ADMIN_ACCESS_LOG: /dev/stdout
      KONG_PROXY_ERROR_LOG: /dev/stderr
      KONG_ADMIN_ERROR_LOG: /dev/stderr

      KONG_ADMIN_LISTEN: '0.0.0.0:8001, 0.0.0.0:8444 ssl'
    networks:
      - kong-net
    ports:
      - "8000:8000"
      - "8443:8443"
      - "127.0.0.1:8001:8001"
      - "127.0.0.1:8444:8444"
    restart: on-failure

networks:
  kong-net:
    name: kong-network

When I try to call my endpoint (which I’m running locally), I get this error message:

kong_1  | 2021/10/07 22:09:47 [error] 1097#0: *105 connect() failed (111: Connection refused) while connecting to upstream, client: 172.19.0.1, server: kong, request: "POST /registrations HTTP/1.1", upstream: "http://127.0.0.1:4556/", host: "127.0.0.1:8000"
kong_1  | 2021/10/07 22:09:47 [error] 1097#0: *105 connect() failed (111: Connection refused) while connecting to upstream, client: 172.19.0.1, server: kong, request: "POST /registrations HTTP/1.1", upstream: "http://127.0.0.1:4556/", host: "127.0.0.1:8000"
kong_1  | 2021/10/07 22:09:47 [error] 1097#0: *105 connect() failed (111: Connection refused) while connecting to upstream, client: 172.19.0.1, server: kong, request: "POST /registrations HTTP/1.1", upstream: "http://127.0.0.1:4556/", host: "127.0.0.1:8000"
kong_1  | 2021/10/07 22:09:47 [error] 1097#0: *105 connect() failed (111: Connection refused) while connecting to upstream, client: 172.19.0.1, server: kong, request: "POST /registrations HTTP/1.1", upstream: "http://127.0.0.1:4556/", host: "127.0.0.1:8000"
kong_1  | 2021/10/07 22:09:47 [error] 1097#0: *105 connect() failed (111: Connection refused) while connecting to upstream, client: 172.19.0.1, server: kong, request: "POST /registrations HTTP/1.1", upstream: "http://127.0.0.1:4556/", host: "127.0.0.1:8000"
kong_1  | 2021/10/07 22:09:47 [error] 1097#0: *105 connect() failed (111: Connection refused) while connecting to upstream, client: 172.19.0.1, server: kong, request: "POST /registrations HTTP/1.1", upstream: "http://127.0.0.1:4556/", host: "127.0.0.1:8000"
kong_1  | 172.19.0.1 - test_customer_id [07/Oct/2021:22:09:47 +0000] "POST /registrations HTTP/1.1" 502 75 "-" "PostmanRuntime/7.28.1"