Docker need to access hosts's Postgres database

Question

I have a Flask app that's running inside a Docker container, and I can run it using the following command.

docker run -e DB_HOST=<...> -e DB_PORT=<...> -e DB_NAME=<...> -e DB_USER=<...> -e DB_PASSWORD=<...> -p 8080:8080 <tag name>

Before the database was on AWS, now the database is running on a MAC laptop. So how can the Flask app from the docker container to connect to the hosts Postgres' database? What should be my DB_HOST?

I mean `localhost:5432` should work after you pass in `--net=host` ? — ffledgling, Jun 22 '17 at 18:50
If I do this, the flask app is no longer accessible from localhost:8080 on my MAC — user1187968, Jun 22 '17 at 19:05
try to add `127.0.0.1 localdb` to hosts file on MAC and pass `--net=host` as wrote @ffledgling — Bukharov Sergey, Jun 22 '17 at 19:23
From inside the container `localhost` will not point to host's `localhost`. Keep in mind they're in isolated environments. Perhaps this [answer](https://stackoverflow.com/a/31328031/7925366) help you. — Michel Milezzi, Jun 22 '17 at 20:29

score 0 · Answer 1 · answered Jul 18 '18 at 01:32

For security reasons a Postgres server make it hard to connect to it. By default you can connect to the server from localhost and 127.0.0.1.

This does not work from within Docker since localhost refers to the running docker container not your laptop.

You have to connect from Docker to the IP address of your laptop. You can find your laptop's IP on a Mac in System Preference > Network Or you can use ifconfig | grep inet.

You need to modify 2 Postgres config file: postgresql.conf and pg_hba.conf

For file: /usr/local/var/postgres/postgresql.conf

add this line to listen to everything:

listen_addresses = '*' # what IP address(es) to listen on;

Or add your specific laptop IP.

For file /usr/local/var/postgres/pg_hba.conf add a line like this with your IP:

host all all 192.168.1.3/32 md5

Restart the Postgres server when you are done.

Docker need to access hosts's Postgres database

1 Answers1