@Marvin How can I execute code in a standalone docker container from a task? I do not want this docker container to use prefect as a base image; it's completely standalone python.

To execute code in a standalone Docker container from a Prefect task, you don't need to base your container on a Prefect image. You can simply package your Python code into a Docker image and handle the initiation and management of the Docker container within a Prefect task. Here's a high-level overview of how you might accomplish this: 1. Prepare Your Docker Image: Create a Docker image that contains your standalone Python application and all its dependencies. 2. Define a Prefect Task to Run the Container: Write a Prefect task that will use the Docker SDK for Python or a shell command to run your Docker container. For example:

python
   from prefect import task, Flow
   import docker
   
   @task
   def run_docker_container(image_name):
       client = docker.from_env()
       container = client.containers.run(image_name, detach=True)
       return container.logs(stream=True)

   with Flow("docker_flow") as flow:
       run_docker_container(image_name="your-standalone-python-image")
   
   flow.run()

Replace

"your-standalone-python-image"

with the name of your actual Docker image. 3. Deploy and Run Your Flow: Use Prefect's deployment process to execute the defined flow, which in turn will spin up the Docker container and run your standalone code. Remember to configure any necessary environment variables for your container to ensure that it can run as expected, including network configurations if it needs to communicate with external services. Refer to the Prefect documentation if you need more information on how to handle Docker-based storage, deployment, and execution of tasks in Docker containers. The specifics might differ based on your particular setup and requirements.

@Marvin I'm able to do this locally just fine with docker desktop running but the flow fails when deployed to our self hosted instance. Is this because there is no docker daemon available for the docker commands to run against? Specifically, I get the error:

Task run encountered an exception DockerException: Error while fetching server API version: ('Connection aborted.', FileNotFoundError(2, 'No such file or directory'))

The error you're encountering,

DockerException: Error while fetching server API version: ('Connection aborted.', FileNotFoundError(2, 'No such file or directory'))

, typically indicates that your Prefect flow is trying to communicate with a Docker daemon, but it cannot find it. This is likely because your self-hosted instance does not have Docker installed, or the Docker daemon is not accessible to the Prefect agent executing the flow. Some issues on GitHub discuss similar errors (#11802, #9474). In one case, it's mentioned that Docker is not running, which triggers the error during image build. Another case points out a compatibility issue with certain versions of

docker-py

and its dependencies. Here are a few steps to troubleshoot and resolve the issue: 1. Ensure Docker is Installed: Verify that Docker is installed on your self-hosted instance where the Prefect agent is running. 2. Docker Daemon Access: For the Prefect agent to run Docker commands, it needs access to the Docker daemon. You can share the Docker daemon socket with your agent's container by binding

/var/run/docker.sock

. When running the Prefect agent service, you would add a volume bind parameter like

-v /var/run/docker.sock:/var/run/docker.sock

. 3. Using Docker SDK for Python: If you are using the Docker SDK for Python in your task, ensure that it can access the Docker daemon. If accessing via a Unix socket is not possible, consider configuring the SDK to use TCP to connect to the Docker daemon. 4. Check Library Versions: There might be version incompatibilities with the

docker-py

library and its dependencies, such as

requests

and

urllib3

. If you suspect this could be the cause, you may want to consider downgrading these libraries to versions known to be compatible. Based on what has worked for others, you could try the following, assuming you can modify your self-hosted instance's Docker setup: - Start your Prefect agent with the Docker socket shared:

sh
  docker run -v /var/run/docker.sock:/var/run/docker.sock --name prefect-agent prefecthq/prefect:latest agent start

- Check that your user or service has the necessary permissions to access the Docker socket. Make sure to review your Prefect agent setup and deployment strategy according to your self-hosted instance's environment, and adjust accordingly to ensure that Docker can be utilized by the flows being deployed.