Docker connection to PostgreSQL failing from host - postgresql

Question

Spent quite sometime on this but no breakthrough. This is my container creation statement:
> docker create --name aasaan_db_dev -e POSTGRES_USER=aasaan -e
> POSTGRES_PASSWORD=aasaan_admin --expose 5432 postgres:9.4.0
>
> > deepakkt#deepakkt-ubuntu:~$ docker ps
>
> CONTAINER ID IMAGE COMMAND
> CREATED STATUS PORTS NAMES
> 15b21deb19a0 postgres:9.4.0 "/docker-entrypoin..." About
> an hour ago Up About an hour 5432/tcp aasaan_db_dev
The following works:
> deepakkt#deepakkt-ubuntu:~$ docker exec -it aasaan_db_dev psql -U
> aasaan psql (9.4.0) Type "help" for help.
>
> aasaan=#
However, from the host (same error from pgAdmin as well)
> deepakkt#deepakkt-ubuntu:~$ psql -h 127.0.0.1 -U aasaan
Password for user aasaan:
psql: FATAL: password authentication failed for user
> "aasaan" FATAL: password authentication failed for user "aasaan"
Contents of pg_hba.conf inside the container:
# TYPE DATABASE USER ADDRESS METHOD
# "local" is for Unix domain socket connections only
local all all trust
# IPv4 local connections:
host all all 127.0.0.1/32 trust
# IPv6 local connections:
host all all ::1/128 trust
# Allow replication connections from localhost, by a user with the
# replication privilege.
#local replication postgres trust
#host replication postgres 127.0.0.1/32 trust
#host replication postgres ::1/128 trust
host all all 0.0.0.0/0 md5
What am I missing?

Answer 1

It is needed to map the container port to host port.
Have a look at below docker documentation:
The EXPOSE instruction does not actually publish the port. It
functions as a type of documentation between the person who builds the
image and the person who runs the container, about which ports are
intended to be published. To actually publish the port when running
the container, use the -p flag on docker run to publish and map one or
more ports, or the -P flag to publish all exposed ports and map them
to high-order ports.
Source: docker docs

Answer 2

docker ps is showing 5432/tcp for your port section.
This means the port 5432 is opened on your postgres container. (This is by default because it's exposed in the Dockerfile of postgres so you don't need the --expose command).
The name of your container is aasaan_db_dev. Other containers which are deployed in the same bridge network can access your container using aasaan_db_dev:5432.
But your container is not mapping it's port to the outside which means you can not access the container from outside the bridge network. (for example not from eth0).
To map your port use the following command:
docker run --name some-postgres -e POSTGRES_PASSWORD=mysecretpassword -d -p 5432:5432 postgres
In this case the -p option will map 5432 from your container on 5432 of your host. Now you should be able to connect to the container from your host network (for example localhost).

Answer 3

You should not use 127.0.0.1 as it will refer to your localhost. But actually, it is running on a container.
You should use
psql -h <imagename> -U <username>
You need to provide port as well.