Docker compose doesn't connect two containers - postgresql

Question

I have two containers that don't connect to each other:
1. I made an image postgres that get data from dump.sql
here is Dockerfile:
FROM postgres:11.1-alpine
COPY restore_db.sh /docker-entrypoint-initdb.d/
COPY db.sql /backup/
ENV PGDATA=/data
Then I created container with docker run --name db -p 5432:5432 db
4.I made a image with app. Dockerfile for app look like:
# Set the working directory to /app
WORKDIR /app
# Copy the current directory contents into the container at /app
COPY build/libs/ /app/
# Make port 80 available to the world outside this container
EXPOSE 8085
# Define environment variable
ENV NAME app
# Run app when the container launches
CMD java -jar /app/olympic-0.0.1-SNAPSHOT.jar
I made a container with run.
then i use docker-compose up with file that looks like:
version: '3'
services:
db:
image: db-data
container_name: postgres
ports:
- 5432:5432
volumes:
- ./pg_data:/data
environment:
POSTGRES_DB: innovation
POSTGRES_USER: postgres
PGDATA: /data
restart: always
web:
image: app
container_name: roc
environment:
POSTGRES_HOST: db
ports:
- 8085:8085
restart: always
links:
- db
```
here is property file:
```
spring.datasource.url=jdbc:postgresql://db:5432/innovation
spring.datasource.username=postgres
spring.jpa.properties.hibernate.jdbc.lob.non_contextual_creation=true
logging.level.org.hibernate.SQL=DEBUG
logging.level.root=INFO
spring.output.ansi.enabled=ALWAYS
logging.level.org.hibernate.type.descriptor.sql.BasicBinder=TRACE
spring.liquibase.change-log=classpath:liqubase/db.changelog-master.xml
spring.liquibase.url=jdbc:postgresql://db:5432/innovation
spring.liquibase.user=postgres
```
Thet are not able to be connected.
I always got an error:
org.postgresql.util.PSQLException: Connection to db:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.

Answer 1

First of all I dont see any network defined in your Docker files for both containers
So I assume ther are on $project-default network.
docker network inspect $project-default
will give you list of all containers using default network.
Now coming to the containers, Let's assume DB is Container 1 (10.1.1.2) and Spring App is Container 2 (10.1.1.3).
You can get running containers IP by running
docker inspect containerName
You are exposing 5432 and 8085 port for db and Spring respectively
Inside Spring app container property file spring.datasource.url
localhost:5432 or db:5432 (not sure what is db hostname mapped to) is not accessable as DB is in different container.
You can try 10.1.1.2:5432
When you are exposing 5432 and 8085 port from Host machine you can access these port.
eg in Docker for Windows it would be 192.168.99.100:5432
but same cant be access from inside container.
spring.datasource.url=jdbc:postgresql://10.1.1.2:5432/innov should work assuming DB is up and running