Can`t connect to postgres in docker container outside of Python shell

Question

I can`t connect to Postgres image in Docker container outside Python shell.

I have a script, which downloads and rolls out Postgres Docker image. One of the steps is that I would like to create some tables within the database.

If I run the setup.py, it will download the image and install Docker container on the local machine and wait for a connection. If next I will open a Python shell and try to connect to DB - everything works fine.

My Dockerfile:

FROM postgres:11.1
RUN apt-get update
EXPOSE 5432
ENV POSTGRES_DB monitoring
ENV POSTGRES_USER process_monitor

My setup.py file:

import subprocess
import psycopg2


def update_apt():
    subprocess.run(['sudo', 'apt-get', '-y', 'update'])

def install_docker():
    subprocess.run(['sudo', 'apt-get', '-y', 'install', 'docker.io'])

def install_docker_image():
    subprocess.run(['sudo','docker', 'build', '-t', 'postgres-image', '.'])

def docker_run():
    subprocess.run(['sudo', 'docker', 'run', '-p', '5432:5432', '-v', '/var/run/postgresql:/var/run/postgresql', '-d', 'postgres-image'])


if __name__ == "__main__":
    update_apt()
    install_docker()
    install_docker_image()
    docker_run()

Here is what I have in cli when I run this:

Successfully built d7a66c60b43e
Successfully tagged postgres-image:latest
2d1c667a84513943dad359b73962b6314590b1bf79ab4376aa7b513684629e5f

--- Successul built and ran container ---

(venv) simon@simon-HP-EliteBook-840-G2:~/Desktop/Projects/x5-test-task$ sudo docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                    NAMES
2d1c667a8451        postgres-image      "docker-entrypoint.s…"   7 seconds ago       Up 5 seconds        0.0.0.0:5432->5432/tcp   loving_shtern

-- Check if it works ----

(venv) simon@simon-HP-EliteBook-840-G2:~/Desktop/Projects/x5-test-task$ python3
Python 3.6.7 (default, Oct 22 2018, 11:32:17)
[GCC 8.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import psycopg2
>>> conn = psycopg2.connect(dbname='monitoring', user='process_monitor')
>>> cur = conn.cursor()
>>> cur.execute('SELECT datname FROM pg_database')
>>> cur.fetchall()
[('postgres',), ('monitoring',), ('template1',), ('template0',)]
>>> exit()

--- as you can see, there is a monitoring database I need ---

See, the successful connection from Python shell.

But when I tried to add the same code I checked in shell, i get the error:

if __name__ == "__main__":
    update_apt()
    install_docker()
    install_docker_image()
    docker_run()
    conn = psycopg2.connect(dbname='monitoring', user='process_monitor')

Traceback (most recent call last):
  File "setup.py", line 58, in <module>
    conn = psycopg2.connect(dbname='monitoring', user='process_monitor')
  File "/home/simon/Desktop/Projects/x5-test-task/venv/lib/python3.6/site-packages/psycopg2/__init__.py", line 130, in connect
    conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
psycopg2.OperationalError: could not connect to server: No such file or directory
        Is the server running locally and accepting
        connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?

Can't figure out, why I can`t connect from the same script. Should I add some sleep time?

Edit1: it seems lite it is the problem of timing. Tried sleep(60) successfully connected.

jazgot · Accepted Answer · 2019-02-03 22:25:44Z

2

The problem is that you try to connect right after initiating database start. There is some time between container start and moment when database starts accepting connections. You can either wait fixed amount of time with sleep or create loop which will check if db port is open.

answered Feb 3, 2019 at 22:25

jazgot

2,07315 silver badges25 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Simon Osipov Over a year ago

Yep, that is correct. Also, that led me to proper creation of database via SQL scripts inside docker.

Simon Osipov · Accepted Answer · 2019-02-04 14:13:26Z

0

After checking with official documentation, I found this:

If there is no database when postgres starts in a container, then postgres will create the default database for you. While this is the expected behavior of postgres, this means that it will not accept incoming connections during that time. This may cause issues when using automation tools, such as docker-compose, that start several containers simultaneously.

That means, for several seconds right after the start of the container you can`t connect to postgres.

answered Feb 4, 2019 at 14:13

Simon Osipov

4241 gold badge6 silver badges22 bronze badges

Comments

Ajay Rawat · Accepted Answer · 2019-07-11 16:29:59Z

0

Check this link for docker Setup PythonAPI with Postgres: https://github.com/ajayrawat12/DockerPythonFalconPostgres

you can expose db port in docker-compose.yml file, then can use it in connection from anywhere using dbclient as 127.0.0.1:5432

answered Jul 11, 2019 at 16:29

Ajay Rawat

1721 gold badge2 silver badges12 bronze badges

1 Comment

Simon Osipov Over a year ago

Sorry, that is not what this question was about.

Collectives™ on Stack Overflow

Can`t connect to postgres in docker container outside of Python shell

3 Answers 3

1 Comment

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related