Deploying Dash app via Docker container

Dash Python
1

I have the following folder structure:

app_name:
index.py
app.py
Dockerfile

app.py looks like so:

from dash import Dash

# meta_tags are required for the app layout to be mobile responsive
app = Dash(
    __name__,
    suppress_callback_exceptions=True,
    meta_tags=[
        {"name": "viewport", "content": "width=device-width, initial-scale=1.0"}
    ],

    update_title=None,
)

server = app.server

and index.py looks like so:

from app import app, server
app.layout = ....
app.callbacks etc

if __name__ == "__main__":
    app.run_server(
        host="127.0.0.1", port="8050", debug=False, dev_tools_hot_reload=False
    )

Finally, the Dockerfile looks like so:

FROM python:3.10

# Copy local code to the container image.
ENV APP_HOME /app
ENV PYTHONUNBUFFERED True
ENV SQLALCHEMY_SILENCE_UBER_WARNING 1
WORKDIR $APP_HOME


COPY requirements.txt /app/
RUN pip install -r requirements.txt
RUN pip install --no-cache-dir gunicorn
# Install Python dependencies and Gunicorn
# COPY poetry.lock pyproject.toml /app/
# RUN pip3 install --no-cache-dir poetry==1.6.1 \
#     && poetry config virtualenvs.create false \
#     && poetry install --no-root
RUN groupadd -r app && useradd -r -g app app


# ADD requirements.txt .
# RUN pip install --no-cache-dir -r requirements.txt && pip install --no-cache-dir gunicorn

# Copy the rest of the codebase into the image
COPY --chown=app:app . ./
USER app

EXPOSE 80
EXPOSE 443
EXPOSE 8080
# Run the web service on container startup. Here we use the gunicorn
# webserver, with one worker process and 8 threads.
# For environments with multiple CPU cores, increase the number of workers
# to be equal to the cores available in Cloud Run.

#--log-level info --workers 1 --threads 8 --timeout 0 index:server

CMD exec gunicorn --bind :8080 --log-level info index:server

However, I am finding that when I run

docker run <image_id>

[2024-07-29 04:46:20 +0000] [1] [INFO] Starting gunicorn 21.2.0
[2024-07-29 04:46:20 +0000] [1] [INFO] Listening at: http://0.0.0.0:8080 (1)
[2024-07-29 04:46:20 +0000] [1] [INFO] Using worker: sync
[2024-07-29 04:46:20 +0000] [7] [INFO] Booting worker with pid: 7

but when I visit http://0.0.0.0:8080 I receive nothing. What could the problem be?

Deeply appreciate any guidance, thank you

2

It looks like you forgot to map the port. To enable access to the app, you must either run in host mode, or map relevant ports explicitly. In your case that would be to add the argument ‘-p 8080:8080’ to the docker run command.

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