CODEWITHSUNDEEP
dockerportfastapi
W.P. McNeill
W.P. McNeill

Reputation: 17026

Docker Port Forwarding for FastAPI REST API

I have a simple FastAPI project called toyrest that runs a trivial API. The code looks like this.

from fastapi import FastAPI

__version__ = "1.0.0"

app = FastAPI()


@app.get("/")
def root():
    return "hello"

I've built the usual Python package infrastructure around it. I can install the package. If I run uvicorn toyrest:app the server launches on port 8000 and everything works.

Now I'm trying to get this to run in a Docker image. I have the following Dockerfile.

# syntax=docker/dockerfile:1

FROM python:3

# Create a user.
RUN useradd --user-group --system --create-home --no-log-init user
USER user
ENV PATH=/home/user/.local/bin:$PATH

# Install the API.
WORKDIR /home/user
COPY --chown=user:user . ./toyrest
RUN python -m pip install --upgrade pip && \
    pip install -r toyrest/requirements.txt
RUN pip install toyrest/ && \
    rm -rf /home/user/toyrest


CMD ["uvicorn", "toyrest:app"]

I build the Docker image and run it, forwarding port 8000 to the running container.

docker run -p 8000:8000 toyrest:1.0.0
INFO:     Started server process [1]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)

When I try to connect to http://127.0.0.1:8000/ I get no response.

Presumably I am doing the port forwarding incorrectly. I've tried various permutations of the port forwarding argument (e.g. -p 8000, -p 127.0.0.1:8000:8000) to no avail.

This is such a basic Docker command that I can't see how I'm getting it wrong, but somehow I am. What am I doing wrong?

Upvotes: 2

Views: 2876

Answers (1)

Mouad Slimane
Mouad Slimane

Reputation: 1067

try to add this line to yourCMD in ̀dockerfile`:

CMD ["uvicorn", "toyrest:app","--host", "0.0.0.0"]

EDIT

The reason this works is because this makes uvicorn run inside the container on 0.0.0.0 NOT on 127.0.0.1

0.0.0.0 is exposed by docker because it is the private network interface of the docker container. You cannot SEE 127.0.0.1 from outside the container.

Upvotes: 4

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