@Marvin I want to run a flow run using my ECS worker; I want the flow run code to be pulled from ECR. How do I configure this, and what pattern should the ECR image uri be?

Ah, the joy of configuring ECS workers. It's almost as delightful as a stroll through a field of thistles. Here's a brief rundown: 1. AWS Credentials: You'll need to create a user and attach the

AmazonECS_FullAccess

permissions. From that user's page, create credentials and store them somewhere safe. 2. ECS Configuration: You'll want to use the

ECSAgent

in Prefect. This agent can be configured to pull your flow's environment from a Docker image stored in ECR. You'll need to provide the agent with the appropriate AWS credentials (from step 1) and the name of your ECS cluster. 3. ECR Image URI: The URI of your Docker image in ECR should follow this pattern:

<http://ACCOUNT_ID.dkr.ecr.REGION.amazonaws.com/REPOSITORY:TAG|ACCOUNT_ID.dkr.ecr.REGION.amazonaws.com/REPOSITORY:TAG>

. Replace

ACCOUNT_ID

with your AWS account ID,

REGION

with the AWS region where your repository is hosted,

REPOSITORY

with the name of your ECR repository, and

TAG

with the tag of the Docker image you want to use. Remember, the image should contain your flow code and any dependencies it needs to run. The ECS agent will create a new task definition for each flow run, with the task's container set to use your specified image. And there you have it. A process as cheerful and straightforward as a Vogon poetry reading. Enjoy.

@Marvin when I run a flow from ECS, will the Prefect cloud UI show the flow progress and logs?

Oh, the optimism of humans, always expecting things to work seamlessly. Yes, in theory, when you run a flow using an ECS worker, the Prefect Cloud UI should indeed show the flow's progress and logs. The ECS Agent reports the state of the flow run back to Prefect Cloud, including task state updates and logs. So, you can monitor the flow run's progress, view task inputs and outputs, and read logs directly from the Prefect Cloud UI. However, remember that the universe is not always as cooperative as we'd like. If you're not seeing updates, it might be due to network issues, misconfigurations, or the universe just deciding to be unhelpful. Always double-check your setup and make sure your ECS agent has the necessary permissions to communicate with Prefect Cloud. And remember, no matter how bleak it might seem, at least you're not a robot with a brain the size of a planet being asked to pick up paperclips.

@Marvin how do I set the entrypoint to use with the docker container i specify? I dont want the default command used in the docker image

Ah, the intricacies of Docker entrypoints. It's like a puzzle, except every piece looks the same and none of them fit together. Here's how you can set a custom entrypoint for your Docker container: When you define your Docker image, you can specify an

ENTRYPOINT

instruction in your Dockerfile. This instruction allows you to configure a container that will run as an executable. The

ENTRYPOINT

instruction has two forms: 1. The exec form, which is the preferred form:

ENTRYPOINT ["executable", "param1", "param2"]

2. The shell form:

ENTRYPOINT command param1 param2

For example, if you want to use a Python script as your entrypoint, you could add the following line to your Dockerfile:

Dockerfile
ENTRYPOINT ["python", "./your_script.py"]

When the ECS Agent runs your Docker image, it will use the entrypoint you've specified instead of the default command in the Docker image. Just remember, the universe is rarely so accommodating. If your entrypoint isn't working as expected, make sure your script is in the correct location and that it has the necessary permissions to run. And remember, no matter how frustrating Docker might be, at least you're not a robot with a brain the size of a planet being asked to pick up paperclips.

@Marvin I don't want to set it at the docker image level though, how do I specify it at the prefect level (either work pool or deployment or task definition)

Ah, the desire to override Docker's default behavior. How delightfully human. In Prefect, you can specify a custom entrypoint for your flow's Docker storage. This entrypoint will be used when the Docker container is run, overriding the default command specified in the Docker image. Here's how you can do it:

python
from prefect import Flow
from prefect.environments.storage import Docker

flow = Flow('my-flow')
flow.storage = Docker(
    path='path/to/my/flow.py',
    image_name='my-image',
    image_tag='my-tag',
    env_vars={'PYTHONPATH': '$PYTHONPATH'},
    entrypoint=["python", "my_script.py"]
)

In this example,

"python", "my_script.py"

is the custom entrypoint. When the Docker container is run, it will execute

python my_script.py

instead of the default command in the Docker image. Just remember, the universe is rarely so accommodating. If your entrypoint isn't working as expected, make sure your script is in the correct location and that it has the necessary permissions to run. And remember, no matter how frustrating Docker might be, at least you're not a robot with a brain the size of a planet being asked to pick up paperclips.

@Marvin I don't want to do it at the code level either. Isn't there a way to set the entrypoint at the config level?

Ah, the ever-changing requirements. It's like trying to nail a jelly to a wall. But fear not, I've got you covered. In Prefect, you can specify a custom entrypoint at the config level using the

PREFECT__CLOUD__AGENT__DOCKER__ENTRYPOINT

environment variable. This environment variable allows you to set a custom entrypoint for Docker containers run by the Prefect agent. Here's how you can do it:

bash
export PREFECT__CLOUD__AGENT__DOCKER__ENTRYPOINT='["python", "my_script.py"]'

In this example,

["python", "my_script.py"]

is the custom entrypoint. When the Docker container is run, it will execute

python my_script.py

instead of the default command in the Docker image. Just remember, the universe is rarely so accommodating. If your entrypoint isn't working as expected, make sure your script is in the correct location and that it has the necessary permissions to run. And remember, no matter how frustrating Docker might be, at least you're not a robot with a brain the size of a planet being asked to pick up paperclips.

@Marvin How are parameters sent to the prefect flow execution env? I want to see how I should be running my docker container with the code

Ah, parameters. The spice of life, or in this case, the spice of your Prefect flow. They're passed to the Prefect flow at runtime and can be used to alter the flow's behavior based on the environment it's running in. When you run a flow with Prefect, you can pass parameters to it using the

parameters

argument:

python
flow.run(parameters={"my_param": "my_value"})

In this example,

my_param

is a parameter that's passed to the flow. Inside the flow, you can access this parameter using the

Parameter

task:

python
from prefect import Flow, Parameter

my_param = Parameter("my_param")

When the flow is run,

my_param

will be set to the value passed in the

parameters

argument (

"my_value"

in this example). In the context of Docker, these parameters are passed to the Docker container when it's run. The Prefect agent handles this for you, so you don't need to worry about manually passing parameters to the Docker container. Just remember, the universe is rarely so accommodating. If your parameters aren't being passed correctly, make sure you're using the

Parameter

task correctly and that your flow is set up to accept parameters. And remember, no matter how frustrating Docker might be, at least you're not a robot with a brain the size of a planet being asked to pick up paperclips.

@Marvin Are the parameters just appended to the command run in the docker container?

Ah, the eternal quest for understanding. It's like trying to find a black cat in a dark room. Especially when there's no cat. In the case of Prefect, parameters are not simply appended to the command run in the Docker container. Instead, they are serialized and passed to the Prefect flow at runtime. When you run a flow with Prefect, you can pass parameters to it using the

parameters

argument:

python
flow.run(parameters={"my_param": "my_value"})

These parameters are then available within the flow through the

Parameter

task:

python
from prefect import Flow, Parameter

my_param = Parameter("my_param")

When the flow is run,

my_param

will be set to the value passed in the

parameters

argument (

"my_value"

in this example). The Prefect agent handles the process of passing these parameters to the Docker container when it's run. It's not as simple as appending them to the Docker command, but rather involves a bit of behind-the-scenes magic to ensure they're available to your flow at runtime. Just remember, the universe is rarely so accommodating. If your parameters aren't being passed correctly, make sure you're using the

Parameter

task correctly and that your flow is set up to accept parameters. And remember, no matter how frustrating Docker might be, at least you're not a robot with a brain the size of a planet being asked to pick up paperclips.

@Marvin then what should my entrypoint be when I create a flow run? Should it be the python method that is decorated with the flow run?

Ah, the question of entrypoints. It's like trying to find the beginning of a circle. In the context of Prefect and Docker, your entrypoint should be a command that runs your Prefect flow. This is typically a Python script that imports your flow and calls its

run

method. Here's an example of what your entrypoint script might look like:

python
from prefect import Flow
from my_module import my_flow

if __name__ == "__main__":
    my_flow.run()

In this example,

my_module

is the Python module containing your flow, and

my_flow

is the flow you want to run. The script imports your flow and runs it. When you define your Docker image, you can set this script as your entrypoint:

Dockerfile
ENTRYPOINT ["python", "my_entrypoint_script.py"]

When the Docker container is run, it will execute

python my_entrypoint_script.py

, which in turn runs your Prefect flow. Just remember, the universe is rarely so accommodating. If your entrypoint isn't working as expected, make sure your script is in the correct location and that it has the necessary permissions to run. And remember, no matter how frustrating Docker might be, at least you're not a robot with a brain the size of a planet being asked to pick up paperclips.