Cannot get Bash script output in Celery Worker inside Docker Container

Question

I am literally pulling my hair out over this problem. Recently I have started working on a Remote Code Execution service.

The service sends the following payload to a Celery worker:

{
 "language": "python",
 "code": "print('Hello World!')"
}

The service expects to receive back the output of the code.

The Celery worker runs in a docker container, with the following Dockerfile :

FROM python:3.9-slim-buster

ENV PYTHONDONTWRITEBYTECODE=1
ENV PYTHONBUFFERED 1

RUN mkdir /worker
WORKDIR /worker

COPY requirements.txt /worker/


RUN /usr/local/bin/python -m pip install --upgrade pip

RUN pip install -r /worker/requirements.txt

COPY . /worker/

For the service and worker I am using ths docker-compose file:

version: "3"

services:
  rabbit:
    image: rabbitmq:latest
    ports:
      - "5672:5672"
  api:
    build: app/
    command: uvicorn remote_coding_compilation_engine.main:app --host 0.0.0.0 --reload
    volumes:
      - ./app:/app
    ports:
      - "8000:8000"

  worker:
    build: worker/
    command: watchmedo auto-restart --directory=./ --pattern=*.py --recursive -- celery --app=worker.celery_app worker -c 2 --loglevel=INFO
    #celery --app=worker.celery_app worker -c 2 --loglevel=INFO
    volumes:
      - ./worker:/worker
    depends_on:
      - api
      - rabbit

  flower:
    image: mher/flower
    command: ["flower", "--broker=pyamqp://guest@rabbit//", "--port=8888"]
    ports:
      - "8888:8888"
    depends_on:
      - api
      - rabbit
      - worker

The worker creates a .py file with the code given in the payload and then runs a bash script to execute the code, the code output should be automatically redirected to an out_file from python. However I am not able to get the output of the bash script.

This is the bash script:

#!/bin/bash 

if [ $# -lt 1 ]
then
    echo "No code running command provided!"
else
    eval $@
fi

I am passing the follwoing arguments to this script: python path_to_file

This is the worker code which runs the bash script:

def execute_code(cls, command: str, out_file_path: str) -> None:
        """
        Function which execudes the given command and outputs the result in the given out_file_path

        @param command: command to be executed
        @param out_file_path: path to the output file

        @return None

        @raise: FileNotFoundError if the command does not exist
        @raise: IOError if the output file cannot be created
        @raise: CalledProcessError if the command fails to be executed
        """
        try:
            logging.info(f"Creating output file: {out_file_path}")
            with open(out_file_path, "w+") as out_file_desc:

                logging.info(f"Creating process with command: {command} and output_file: {out_file_path}")
                os.chmod(cls.EXECUTE_CODE_SCRIPT_PATH, 0o755)

                rc = subprocess.call(command, shell=True, stdout=out_file_desc, stderr=out_file_desc)

                logging.info(f"Commandmd: {command.split()}")
                logging.info(f"Return Code: {rc}")
                logging.info(f"OutFile Content: {out_file_desc.read()}")

                if rc != 0:
                    logging.debug(f"Command execution was errored: {out_file_desc.read()}")
                    raise subprocess.CalledProcessError(rc, command)

        except FileNotFoundError as fnf:
            logging.error(
                f"Command not found: {command}"
            )
            raise fnf
        except IOError as ioe:
            logging.error(
                f"Could not create output file: {out_file_path}"
            )
            raise ioe
        except subprocess.CalledProcessError as cpe:
            logging.error(
                f"Process exited with error: {cpe.output}"
            )
            raise cpe

Obs1. The command to be executed in subprocess.call is in the form /worker/execute_code/code_execute.sh python /worker/tmp/in_files/some_file_name.py

Obs2. I am sure the script runs the command since, for example if I alter the path to folder containing the code to be executed I am getting a "FileNotFound" error.

Obs3. If instead of "$@" I am using literally python <<hardcoded_path>>, I can see the output of the bash script

Obs4. The running entity has rw access on the output file. I cannot get the output of the script even if I use the default stdout

What I've tried:

• Firstly I didn't want to use a bash script, I wanted to use subprocess.run, but again I was unable to get the output
• If I call the script using the terminal, I get the code output

Any help would be appreciated, thank you!

Answer 1

I believe you were right in your initial intuition to not have to maintain a bash file at all. If I understand correctly what you're trying to do (execute the command, write the output to a file), this does that without maintaining a bash script or writing the command to an input file to begin with:

def execute_code(command="print('Hello World')", out_file_path='/home/geo/result.txt'):
    with open(out_file_path, 'w+') as f:
        subprocess.Popen(["python", "-c", command], stdout=f)

You should see the output in result.txt .