Can't connect to Spring Boot app running on Docker locally - spring-boot

Question

I stuck with the problem that can't open my REST Spring Boot app on localhost:8091 in browser.
Here is my docker-compose.xml (everything is deployed locally on Docker Desktop):
version: '3.3'
services:
postgres:
build:
context: services/postgres
dockerfile: Dockerfile.development
command: postgres
ports:
- "5432:5432"
environment:
- POSTGRESS_USER=postgres
- POSTGRESS_DB=postgres
- POSTGRESS_PASSWORD=qqq
- POSTGRES_HOST_AUTH_METHOD=trust
volumes:
- "db-data:/var/lib/postgresql/data"
app:
build:
context: services/app
dockerfile: Dockerfile.development
command: java -jar ./app.jar
environment:
- PORT=8091
network_mode: host
image: 'my-java-app'
ports:
- 8091:8091
depends_on:
- postgres
angular:
build:
context: services/angularfrontend
dockerfile: Dockerfile.development
image: 'my-angular-app'
ports:
- 80:80
volumes:
db-data:
Spring Boot App starts normally on 8091 and connects to the database, but then I can't make calls to it's API from my local machine ("connection refused").
Angular app opens normally (on localhost:80), but can't make calls to localhost:8091 Spring Boot app.

Answer 1

The call from angular service container to localhost:8091 fails, right?
Try to override in your angular frontend container the call to the backend
use app:8091 (this is how the backend service is called) instead of localhost:8091.
In the 'angular' container localhost doesn't translate to 'app' container.
You can't get from a container into a different container using localhost.
localhost inside a container will translate to the ip of that container.
Try to make in your angular application the call to the backend configurable, after that override that configuration in docker-compose using environment.
Also do that for the springboot app application.
I don't see in the environment that you override the call to the postgress.
Expose that configuration in application.properties and override in docker-compose, after that remove network_mode: host

Answer 2

If you really want to use network_mode: host, you don't need to specify <source>:<dest> because the app is listening on 8091 directly on the host network:
...
app:
build:
context: services/app
dockerfile: Dockerfile.development
command: java -jar ./app.jar
environment:
- PORT=8091
network_mode: host
image: 'my-java-app'
depends_on:
- postgres
...
If you want to run the java app like the other containers, simply remove this line from the compose file and the network mode will default to bridge:
network_mode: host