Pfthb

I am working with a project that uses express as the server and postgres as the db to learn dockers.
the server depends on the db to be up.
The first time i use docker-compose up it all works fine but when i restart it
(docker-compose down and docker-compose up again) it says that something is wrong with the port

version: '3'
services:
 db:
 image: postgres:10
 ports:
 - "5433:5432"
 environment:
 POSTGRES_USER: 'Donald'
 POSTGRES_PASSWORD: 'Aa123456'
 POSTGRES_DB: 'twitter'

 backend:
 build: twitter
 ports: 
 - "3000:3000"
 depends_on: 
 - db
 environment:
 PGHOST: "db"
 PGPORT: '5432'
 PGDATABASE: 'twitter'
 PGUSER: 'Donald'
 PGPASSWORD: 'Aa123456'

The error

 code: 'ECONNREFUSED',
backend_1 

ports before docker-compose down

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
b000b9a02257 excer_backend "node server" 5 minutes ago Up 3 minutes 0.0.0.0:3000->3000/tcp excer_backend_1
40ca65adcc46 postgres:10 "docker-entrypoint.s…" 5 minutes ago Up 3 minutes 0.0.0.0:5433->5432/tcp excer_db_1

after i use docker-compose down and see the ports its all clean and no open ports are left

Than i found something very interesting a when i used docker-compose up it always worked if i use ctr + c and use compose up again still work same when i restart docker but as soon as i use docker-compose down the error is shown.
I tried man combinations with restarting my docker and ctr + c and compose-up
all worked but as soon as i use docker-compose down it dosent work why is that ?

Most likely the DB is not up yet.

When you do docker-compose down, it deletes the container and since you aren't using a volume for persistence, the DB has to run through its init process again which will take a few seconds (and hence works when you ctrl+c and docker-compose up again).

Do note that depends_on doesn't wait until the DB is up. You will have to using something like wait-on for that in your backend container.

Another solution would be to use a volume mount for the DB container.