How to use dagster cli in multi container docker deployment in user code container using subprocess.run

In a multi-container Docker deployment, you typically have separate containers for different components of your Dagster deployment, such as the Dagster webserver, Dagster daemon, and user code. When you want to use the Dagster CLI within the user code container, you can do so by executing commands within that container's environment. The

subprocess.run

function in Python allows you to spawn new processes, connect to their input/output/error pipes, and obtain their return codes. To use

subprocess.run

to execute Dagster CLI commands within a Docker container, you would typically need to: 1. Ensure that the Dagster CLI is installed in the user code container. 2. Use the Docker CLI or Docker SDK for Python to execute commands within the container. Here's a general approach based on the documentation: 1. Define a Dockerfile for your user code container that includes the Dagster CLI installation. For example:

Dockerfile FROM python:3.8-slim  # Install Dagster and other dependencies RUN pip install dagster dagster-graphql  # Set the DAGSTER_HOME environment variable ENV DAGSTER_HOME=/opt/dagster/dagster_home  # Copy your Dagster repository code into the container COPY . /opt/dagster/app  # Set the working directory WORKDIR /opt/dagster/app

2. Build and run your user code container as part of your Docker deployment. 3. To execute Dagster CLI commands within the user code container, you can use the

docker exec

command or the Docker SDK for Python. Here's an example using `subprocess.run`:

python import subprocess  # Command to execute within the Docker container dagster_cli_command = ["dagster", "pipeline", "execute", "-f", "my_pipeline.py"]  # Docker exec command to run the Dagster CLI command in the container docker_exec_command = ["docker", "exec", "my_user_code_container"] + dagster_cli_command  # Use subprocess.run to execute the command result = subprocess.run(docker_exec_command, capture_output=True, text=True)  # Print the output and error (if any) print(result.stdout) print(result.stderr)

In this example, replace

"my_user_code_container"

with the actual name or ID of your user code container, and adjust the Dagster CLI command as needed for your specific use case. Please note that this is a general approach and might require adjustments based on your specific deployment setup. The documentation provides examples of Docker deployments and configurations, but does not provide a direct example of using

subprocess.run

to execute Dagster CLI commands within a Docker container. You would need to adapt the general Docker and Python principles to fit your Dagster deployment.