Docker container with Python Web App - Connect to Postgres on Host machine (OSX)

Question

I can connect to my local Postgres DB in my web app, but NOT if I am running the web app inside of a Docker container.

Web app running inside of a Docker container
Postgres running in the Host machine

I am not sure if it is related to the Postgres connection settings or to the Docker network settings.

Follow my settings and commands:

Host:

OSX 10.11.6
PostgreSQL 9.6

Docker container

Docker 1.13.1
Docker-machine 0.9.0
Docker container OS: python:3.6.0-alpine
Python 3.6 + psycopg2==2.7

postgresql.conf:

listen_addresses = '*'

pg_hba.conf

host    all             all             127.0.0.1/32            trust
host    all             all             0.0.0.0/0               trust
host    all             all             172.17.0.0/24           trust
host    all             all             192.168.99.0/24       trust

With Docker network in HOST mode

docker run -i --net=host -h 127.0.0.1 -e POSTGRES_URI=postgresql://127.0.0.1:5432/db my/image

Error:

could not connect to server: Connection refused
Is the server running on host "127.0.0.1" and accepting TCP/IP connections on port 5432?

With Docker network in BRIDGE mode

docker run -i --add-host=dockerhost:`docker-machine ip ${DOCKER_MACHINE}` -e POSTGRES_URI=postgresql://dockerhost:5432/db -p 8000:8000 -p 5432:5432 my/image

Error:

server closed the connection unexpectedly
This probably means the server terminated abnormally before or while processing the request.

Any ideas?

Any particular reason for not running postgres in a container as well? — Roman
– Roman, Commented Mar 4, 2017 at 3:17

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

There is a note about doing this in the docs

I want to connect from a container to a service on the host

The Mac has a changing IP address (or none if you have no network access). Our current recommendation is to attach an unused IP to the lo0 interface on the Mac; for example: sudo ifconfig lo0 alias 10.200.10.1/24, and make sure that your service is listening on this address or 0.0.0.0 (ie not 127.0.0.1). Then containers can connect to this address.

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Mar 4, 2017 at 3:25

Roman

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2 Comments

Paulo Cheque Over a year ago

I was able to connect to the external service with this tip, thanks! I missed that.

Roman Over a year ago

@PauloCheque, glad I could help. Don't forget to mark answers that solve your problem as correct. That helps other people who come across your question.

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