@Marvin I'd like to build my own prefect images, not have prefect do it. What are the requirements for these images, e.g. what should the CMD be, do I have to use a prefect image as the base image?

Building your own Prefect image involves having specific requirements to ensure compatibility with Prefect's deployment and runtime environment. Here are the key considerations: 1. Base Image: It is not mandatory to use Prefect's provided base images. However, using Prefect's images ensures that all necessary dependencies are pre-installed. If you opt for a different base image, you must ensure to install Prefect within your Dockerfile. 2. CMD Requirement: The CMD specified in your Dockerfile should match how Prefect workers launch. Typically, the CMD should start the worker process. For instance, CMD [ "prefect", "worker", "start" ] 3. Dependencies: Ensure all required Python dependencies for your flows are installed in the image. This can be done by including a

requirements.txt

file or similar within your Dockerfile. 4. Flow Code Access: Your flow code must be accessible in the container. Prefect typically copies the current directory into the Docker image and installs necessary dependencies. Ensure your Dockerfile includes steps to COPY your code and necessary files. ### Example Dockerfile Here’s a basic structure for a Dockerfile to use as a reference:

# Use an appropriate base image
FROM python:3.9-slim

# Install Prefect
RUN pip install prefect

# Copy your flow code and dependencies
COPY . /app
WORKDIR /app

# Install dependencies
RUN pip install -r requirements.txt

# Specify the CMD to start a Prefect worker
CMD ["prefect", "worker", "start"]

### References For detailed guides and advanced configurations, you can refer to the following resources: - Using Prefect with Docker: Prefect Docker Guide - Deployment Details: Deployments Guide

@Marvin Can you explain how the image is used as a runtime environment but deployments need to define an entrypoint? Does that entrypoint file get copied into the image while it's starting up? Is that entrypoint file expected to already be in the image?

To clarify how Prefect uses Docker images as runtime environments and manages entrypoints for deployments: ### Runtime Environment When you use a Docker image as the runtime environment for your Prefect flow, the image contains all the dependencies and setup required for executing the flow. ### EntryPoint The entrypoint specified in your deployment is the path to the Python file and function that contains your flow definitions. This entrypoint is essential because it tells Prefect where to find and how to execute your flow within the container. ### Key Points 1. Image Preparation: - Base Image: You can use a Prefect base image or any other image, provided it contains Prefect and any required dependencies. - Copy Code: Ensure your flow code and dependencies are copied into the image during the build process. This is typically done using the COPY command in your Dockerfile. 2. Deployment: - Dockerfile: When you deploy with Prefect, you can specify a Dockerfile that builds an image with your flow code baked in. Alternatively, you can provide an existing image where the flow code is already present. - Entrypoint in Deployment: The entrypoint file must be present in the Docker image. This file is not dynamically copied during deployment; it should already reside within the image. 3. CMD in Docker: - The CMD in the Dockerfile should start the Prefect worker, which will manage executing the flows. ### Example Here’s an example of how this setup might look in a Dockerfile and deployment YAML: Dockerfile:

FROM python:3.9-slim

# Install Prefect
RUN pip install prefect

# Copy your flow code into the image
COPY . /app
WORKDIR /app

# Install dependencies
RUN pip install -r requirements.txt

# Specify the CMD to start a Prefect worker
CMD ["prefect", "worker", "start"]

Deployment YAML (prefect.yaml):

yaml
name: my_flow
prefect-version: 2.0

# Docker-specific build steps
build:
  - prefect_docker.deployments.steps.build_docker_image:
      requires: prefect-docker>=0.3.0
      image_name: my_registry/my_custom_image
      tag: latest
      dockerfile: auto
      push: true

# Deployment configuration
deployments:
  - name: my-deployment
    entrypoint: flows/my_flow.py:my_flow_function  # Entry point already in image
    image: my_registry/my_custom_image:latest
    work_pool:
      name: my-docker-pool
      work_queue_name: default

### Relevant Documentation - Prefect Docker Guide - Deployments Guide This setup ensures that when the docker image starts, it has everything it needs to run the specified flow using the provided entrypoint. If you have any specific errors or need further details, feel free to ask.