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flask app service can't connect to postgres service within docker-compose

I am trying to run flask, postgres and nginx services with following docker-compose:
version: '3.6'
services:
postgres:
image: postgres:10.5
container_name: postgres
hostname: postgres
user: postgres
ports:
- "5432:5432"
networks:
- db-tier
environment:
CUSTOM_CONFIG: /etc/postgres/postgresql.conf
volumes:
- ./postgres/sql/create_tables.sql:/docker-entrypoint-initdb.d/create_tables.sql
- ./postgres/postgresql.conf:/etc/postgres/postgresql.conf
command: postgres -c config_file=/etc/postgres/postgresql.conf
restart: always
app:
image: python/app:0.0.1
container_name: app
hostname: app
build:
context: .
dockerfile: Dockerfile
depends_on:
- postgres
networks:
- app-tier
- db-tier
stdin_open: true
nginx:
image: nginx:1.22
container_name: nginx-reverse-proxy-flask
ports:
- "8080:80"
depends_on:
- app
volumes:
- ./nginx/nginx.conf:/etc/nginx/nginx.conf:ro
networks:
- app-tier
networks:
app-tier:
driver: bridge
db-tier:
driver: bridge
This is what app.config["SQLALCHEMY_DATABASE_URI"] equals to postgresql://denis:1234Five#postgres:5432/app
The error after docker-compose up is:
app | psycopg2.OperationalError: could not connect to server: Connection refused
app | Is the server running on host "postgres" (192.168.32.2) and accepting
app | TCP/IP connections on port 5432?
What could cause this type of error? I double checked the container name of postgres service, and it running with this name postgres why flask app doesn't "see" it?

It could be issue with no propper startup probe in your postgres container and docker-compose.yml
Look at for reference how to setup them at Docker - check if postgres is ready
So after postgres starts as container, docker starts your app, but postgres inside of container is not ready yet and you get your error

This issue was resolved with postgres pg_isready adding following lines to postgres service:
healthcheck:
test: ["CMD-SHELL", "sh -c 'pg_isready -U ${POSTGRES_USER} -d ${POSTGRES_DB}'"]
interval: 10s
timeout: 3s
retries: 3
Took as solution from here Safe ways to specify postgres parameters for healthchecks in docker compose

Properly migrating Postgres database to Docker/Django/Heroku/Postgres

I have a Django project hosted on an IIS server with a Postgresql database that I am migrating to Docker/Heroku project. I have found a few good resources online, but no luck yet completely. I have tried to use the dumpdata/loaddata function but always run into constraint errors, missing relations, or content type errors. I would like to just dump the whole database and then restore the whole thing to Docker. Here is my docker-compose:
version: "3.7"
services:
db:
image: postgres
volumes:
- 'postgres:/var/lib/postgresql/data'
ports:
- "5432:5432"
environment:
- POSTGRES_NAME=${DATABASE_NAME}
- POSTGRES_USER=${DATABASE_USER}
- POSTGRES_PASSWORD=${DATABASE_PASSWORD}
- POSTGRES_DB=${DATABASE_NAME}
networks:
- hello-world
web:
build: .
command: python manage.py runserver 0.0.0.0:8000
volumes:
- '.:/code'
ports:
- "8000:8000"
env_file:
- .env
depends_on:
- db
networks:
- hello-world
networks:
hello-world:
driver: bridge
volumes:
postgres:
driver: local

I was actually able to resolve this I believe with the following command: "docker exec -i postgres pg_restore --verbose --clean --no-acl --no-owner -h localhost -U postgres -d < ./latest.dump"

How two diffrent docker container api communicate with each other requests?

In one container there Django app running which expose to host port 8000
and another container flask app is running which expose to the host port 8001. So there is a condition where the flask app API end needs to communicate with the Django app API end.
Code
req = requests.get('http://192.168.43.66:8000/api/some')
Error
requests.exceptions.ConnectionError: HTTPConnectionPool(host='192.168.43.66', port=8000): Max retries exceeded with url: /api/user (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7fc6f96942e0>: Failed to establish a new connection: [Errno 110] Connection timed out'))
But if I change the request URL to some other API end which not running on the container it gets the response.
And each Django API end is working fine if I want to access it through some other external source like postman or browser.
Here is the docker-compose file content
Django App docker-compose.yml
version: '3.8'
services:
backend:
build:
context: .
dockerfile: Dockerfile
command: python3 manage.py runserver 0.0.0.0:8000
ports:
- 8000:8000
volumes:
- .:/app
depends_on:
- db
db:
image: mysql:5.7.22
restart: always
environment:
MYSQL_DATABASE: admin
MYSQL_USER: root
MYSQL_PASSWORD: root
MYSQL_ROOT_PASSWORD: root
volumes:
- .dbdata:/var/lib/mysql
ports:
- 33066:3306
flask app docker-compose.yml
version: '3.8'
services:
backend:
build:
context: .
dockerfile: Dockerfile
network: 'host'
command: 'python3 main.py'
ports:
- 8001:5000
volumes:
- .:/app
depends_on:
- db
db:
image: mysql:5.7.22
restart: always
environment:
MYSQL_ROOT_HOST: '%'
MYSQL_DATABASE: main
MYSQL_USER: root
MYSQL_PASSWORD: root
MYSQL_ROOT_PASSWORD: root
volumes:
- .dbdata:/var/lib/mysql
ports:
- 33067:3306
Note: in the project YAML is well formatted so that's not an error.

when you expose a port from container, the host can access it but it doesn't mean other containers can access it too.
you either have to set the network mode to host (which won't work on windows, this is only possible if you're running them on linux).
OR you can run it in a docker-compose and define your own network, here is an example:
version : '3.4'
services:
UI:
container_name: django_app
image: django_image
networks:
my_net:
ipv4_address: 172.26.1.1
ports:
- "8080:8000"
api:
container_name: flask_app
image: flask_image
networks:
my_net:
ipv4_address: 172.26.1.2
networks:
my_net:
ipam:
driver: default
config:
- subnet: 172.26.0.0/16
now your django app can access your flask app on 172.26.1.2
EDIT :
now that you have added your docker-compose files too, you should not create apps in two different docker-compose (that's why you were getting the conflicting ip range error, you were building two networks with same range).
place everything in a single docker-compose, give them ip addresses and you should be fine.
you could make your apps to read ip address of services they relate on from environment variables and then pass these env variables to your container for more flexibility.

Django app exited with code 252 on Docker

I am new to Docker, currently I am trying to deploy my app in a container. I have made 2 containers one for the DB and one for the app. But when I am trying to run my docker-compose file the app container exists with exit code 252. Here are the logs -
web_1 | Watching for file changes with StatReloader
web_1 | Performing system checks...
web_1 |
mushroomxpert_web_1 exited with code 252
This is my docker-compose file
version: '3.7'
services:
web:
image: mushroomxpert
build:
context: ./web
# command: 'gunicorn MushroomXpert.wsgi --log-file -'
command: python manage.py runserver 0.0.0.0:8000
ports:
- '8000:8000'
environment:
- ALLOWED_HOSTS=localhost
- DEBUF=False
- DB_NAME=mushroomxpert_db
- DB_USER=mushroom_admin
- DB_PASSWORD=chikchik1
- DB_HOST=db
- DB_PORT=5432
depends_on:
- db
db:
image: postgres
environment:
- POSTGRES_PASSWORD=chikchik1
- POSTGRES_USER=mushroom_admin
- POSTGRES_DB=mushroomxpert_db
EDIT 1- the problem seems to be occuring from Tensorflow, so I downgraded it's version to 2.2 after that the app worked. I am marking this as solved.

Please use something like this
version: "3.7"
db:
image: postgres
environment:
- POSTGRES_PASSWORD=chikchik1
- POSTGRES_USER=mushroom_admin
- POSTGRES_DB=mushroomxpert_db
expose:
- "5432"
web:
build:
context: ./web
dockerfile: YOUR DOCKERFILE
ports:
- "0.0.0.0:8000:8000"
volumes:
- "./backend/:/app/"
environment:
- ALLOWED_HOSTS: "localhost"
- DEBUG: "False"
- DB_NAME: "mushroomxpert_db"
- DB_USER: "mushroom_admin"
- DB_PASSWORD: "chikchik1"
- DB_HOST: "db"
- DB_PORT: "5432"
env_file:
- config.env
depends_on:
- db
command: >-
sh -c "
pip install -r requirements.txt &&
python manage.py runserver 0.0.0.0:8000
"
The above configuration contains everything that you need and moreover the connection between the db and your django application.

Use docker-compose to push application in Dokku in Digital Ocean

I have a dockerized flask application with 2 services inside docker-compose. How can I use docker-compose to push my application inside of Dokku on Digital Ocean?
version: "3.9"
services:
web:
build: .
container_name: ad
ports:
- "5000:5000"
volumes:
- ".:/app"
scheduler:
image: mcuadros/ofelia:latest
volumes:
- /var/run/docker.sock:/var/run/docker.sock
- ./config.ini:/etc/ofelia/config.ini
depends_on:
- web
I have setup and configured a Dokku droplet. Any help is appreciated.
Resources -
https://dokku.com/docs/deployment/builders/dockerfiles/
https://auth0.com/blog/hosting-applications-using-digitalocean-and-dokku/
https://www.linode.com/docs/guides/deploy-a-flask-application-with-dokku/