Sending API-requests between two docker containers

I have running a DDEV-Environment for Magento2, locally on my Mac OSX (Ventura)

https://ddev.readthedocs.io/en/stable/users/quickstart/#magento-2

For testing purpose I included Nifi per docker-compose.yaml inside my ddev project .ddev/docker-compose.nifi.yaml

Below you can see the docker-compose, which is really minimal at this point. Nifi works like expected, because I can login etc, although it is not persistent yet, but thats a different problem

version: '3'
services:
  nifi:
    image: apache/nifi:latest
    container_name: ddev-${DDEV_SITENAME}-nifi
    ports:
      # HTTP
      - "8080:8080"
      # HTTPS
      - "8443:8443"
    volumes:
        # - ./nifi/database_repository:/opt/nifi/nifi-current/database_repository
        # - ./nifi/flowfile_repository:/opt/nifi/nifi-current/flowfile_repository
        # - ./nifi/content_repository:/opt/nifi/nifi-current/content_repository
        # - ./nifi/provenance_repository:/opt/nifi/nifi-current/provenance_repository
        # - ./nifi/state:/opt/nifi/nifi-current/state
        # - ./nifi/logs:/opt/nifi/nifi-current/logs
        # - ./nifi/conf/login-identity-providers.xml:/opt/nifi/nifi-current/conf/login-identity-providers.xml
        - ".:/mnt/ddev_config"

All I want to do is sending a POST-requst from Nifi to my Magento2 module.

I tried several IPs now, which I got from docker inspect ddev-ddev-magento2-web but I always receive "Connection refused"

My output from docker network ls:

NETWORK ID     NAME                         DRIVER    SCOPE
95bea4031396   bridge                       bridge    local
692b58ca294e   ddev-ddev-magento2_default   bridge    local
46be47991abe   ddev_default                 bridge    local
7e19ae1626f1   host                         host      local
f8f4f1aeef04   nifi_docker_default          bridge    local
dbdba30546d7   nifi_docker_mynetwork        bridge    local
ca12e667b773   none                         null      local

My Magento2-Module is working properly, because sending requests from Postmanto it works fine

You don't want most of what you have. Please remove the ports statement, which you shouldn't need at all; if you need anything, you'll need an expose. But I doubt you need that in this case?

You'll want to look at the docs:

• Additional services and add-ons
• Additional services with docker-compose

Then create a .ddev/docker-compose.nifi.yaml with something like

services:
  nifi:
    image: apache/nifi:latest
    container_name: ddev-${DDEV_SITENAME}-nifi
    container_name: "ddev-${DDEV_SITENAME}-someservice"
    labels:
      com.ddev.site-name: ${DDEV_SITENAME}
      com.ddev.approot: ${DDEV_APPROOT}
    expose:
      - "8080"
    environment:
      - VIRTUAL_HOST=$DDEV_HOSTNAME
      - HTTP_EXPOSE=8080:8080
      - HTTPS_EXPOSE=9999:8080
    volumes:
        - ".:/mnt/ddev_config"

The name of the "web" container from inside your nifi container will be "web", curl http://web:8080, assuming that you have nifi on port 8080.

I don't know what you're trying to accomplish, but this may get you started. Feel free to come over to the DDEV Discord channel for more interactive help.