Can't access docker application from localhost using docker-compose

Question

before I start: I have searched this question already and implemented what the "Solutions" were and it did not help (setting host to 0.0.0.0). So, with that out of the way,

Directory structure

|-- osr
|    |-- __init__.py
|-- requirements.txt
|-- Dockerfile
|-- docker-compose.yml

Dockerfile:

FROM python:3.7.5-buster

EXPOSE 5000 # i have tried with and without this

ENV INSTALL_PATH /osr
ENV FLASK_APP osr
ENV FLASK_ENV development
RUN mkdir -p $INSTALL_PATH

COPY requirements.txt requirements.txt
RUN pip install -r requirements.txt

COPY . .

CMD [ "flask", "run", "--host=0.0.0.0"]

docker-compose.yml:

version: '3.8'
services:
    web:
        build: .
        ports:
            - '5000:5000'
        expose:
            - '5000'
        volumes:
            - .:/osr

__ init __.py

import os
from flask import Flask

def create_app(test_config=None):
    app = Flask(__name__, instance_relative_config=True)
    app.config.from_mapping(
        SECRET_KEY='dev'
    )

    @app.route('/hello')
    def hello():
        return 'Hello, World!'

    return app

docker-compose build web docker-compose run web

 * Serving Flask app "osr" (lazy loading)
 * Environment: development
 * Debug mode: on
 * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 225-441-434

all of the below return "hmm can't reach this page"

http://localhost
http://localhost:5000/hello
http://127.0.0.1:5000/hello

I've even tried going to the containers IP with

docker exec -it 49e677 bash ip add | grep global inet 172.21.0.2/16 brd 172.21.255.255 scope global eth0

http://127.21.0.2:5000/hello # nothing

Nothing.

I'm sure the app itself works fine as I can simply run the app directly.

$env:FLASK_APP="osr"
$env:FLASK_ENV="development"
flask run --host=0.0.0.0

And it runs fine

EDIT: UPDATE

I am actually able to get to the container when I run it through simply the Dockerfile... using

docker run -it -p 5000:5000 osr_web # the container built by docker-compose build

With this, I am able to access the endpoint through localhost:5000/hello

So the issue appears to lie in spinning it up through docker-compose run

Does this help at all?

UPDATE 2

I have discovered that when I run docker ps -a I can see that Docker run actually exposes the port, but docker-compose run does not:

What's your host OS? (Is it more specifically an older Windows where you need Docker Toolbox?) Do you have a firewall setup that might need to be adjusted? — David Maze
– David Maze, Commented May 30, 2020 at 11:01
I am using the most up to date Windows 10, does Windows 10 need to allow firewall for outbound in this regard? — Aserian
– Aserian, Commented May 30, 2020 at 19:22

hariK · Accepted Answer · 2020-06-02 18:36:25Z

2

Are you sure app works fine itself? I tried to run your python __init__.py file and ended up with an error.

python osr/__init__.py 
  File "osr/__init__.py", line 11
    def hello():
    ^
IndentationError: unexpected indent

It works after fixing the indentation error.

@app.route('/hello')
def hello():
    return 'Hello, World!'

$ docker run -d -p 5000:5000 harik8/osr:latest 
76628f86fecb61c0be4a969d3c91c5c575702ad8063b594a6c1c90b498ea25f1

$ curl http://127.0.0.1:5000/hello
Hello, World!

You can't run both docker and docker-compose in port 5000 at the same time. Either run one at a time or change the docker-compose/dockerfile host port.

$ docker ps -a | grep osr
8b885c4a9654        harik8/osr:latest                                     "flask run --host=0.…"   12 seconds ago       Up 11 seconds               0.0.0.0:5000->5000/tcp
$ docker ps -a | grep q5      
70f38bf11e26        q5_web                                                "flask run --host=0.…"   About a minute ago   Up 10 seconds               0.0.0.0:5001->5000/tcp

$ docker ps -a | grep q5
f9f6ba999109        q5_web                                                "flask run --host=0.…"   5 minutes ago       Up 5 minutes                0.0.0.0:5000->5000/tcp                                                                                                   q5_web_1
$ docker ps -a | grep osr
93fb421333e4        harik8/osr:latest                                     "flask run --host=0.…"   18 seconds ago      Up 18 seconds               5000/tcp

edited Jun 2, 2020 at 18:36

answered May 30, 2020 at 9:12

hariK

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6 Comments

Aserian Over a year ago

It was mis-pasted, the tabbing didn't copy over and I had to do it manually, the code is already as you posted, sorry I'll fix it in the question

Aserian Over a year ago

Also, please note the update in the question. This works with docker run as you have shown, but not docker-compose run for some reason.

Aserian Over a year ago

There is no error, I simply can't connect to the endpoint. I posted all the relevant information. It gives no error and starts up as expected. Please review the question.

Aserian Over a year ago

As you can see the first was run with -it . Therefore simply exiting the container stopped it. Changing the port still does nothing and the port is not exposed. Are you using docker-compose in your tests? If not you are not simulating the environment.

hariK Over a year ago

@Aserian Flag it opens a tty session and it keeps the container alive. I was able to simulate the scenario and I have updated the answer.

|

Aserian · Accepted Answer · 2020-05-30 20:44:43Z

I found the issue. For reference, I am running these versions:

docker-compose version 1.25.5, build 8a1c60f6

Docker version 19.03.8, build afacb8b

There were a couple issues: First and foremost to get the ports exposed I needed to run one of two options.

docker-compose up web or docker-compose run --service-ports web

Simply running docker-compose run web would not expose the ports.

Once this was finished, I was able to access the endpoint. However I started getting another odd error,

flask.cli.NoAppException
flask.cli.NoAppException: Failed to find Flask application or factory in module  
"osr". Use "FLASK_APP=osr:name to specify one.

I had not experienced this simply using docker run -it -p 5000:5000 osr_web which was odd. However I noticed I had not set the work directory in the Dockerfile.

I changed the Dockerfile to this:

FROM python:3.7.5-buster

EXPOSE 5000
ENV INSTALL_PATH /osr
ENV FLASK_APP osr
ENV FLASK_ENV development
RUN mkdir -p $INSTALL_PATH

COPY requirements.txt requirements.txt
RUN pip install -r requirements.txt

# added this line
WORKDIR $INSTALL_PATH

COPY . .

CMD [ "flask", "run", "--host=0.0.0.0"]

I believe you could get away without setting the WORK_DIR if you turn the flask application into a package and install it.

gedijedi · Accepted Answer · 2023-12-06 10:51:20Z

1

I ran into similar issue, using docker compose with a target Dockerfile. I took the example from nextjs https://github.com/vercel/next.js/tree/canary/examples/with-docker-multi-env/docker/development

Everything was running correctly, and after some head banging, I noticed that there's a comment about not exposing ports in Dockerfile in their other example:

# Note: Don't expose ports here, Compose will handle that for us https://github.com/vercel/next.js/blob/0082d54893893b71b4be50b1ace748015781c0dc/examples/with-docker-compose/next-app/dev.Dockerfile#L24

I removed these lines from Dockerfile, rebuilt, and it's working now as expected.:

EXPOSE 3000
ENV PORT 3000
ENV HOSTNAME localhost

answered Dec 6, 2023 at 10:51

gedijedi

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