@Marvin in relation to workers; i am getting this error.

A task definition must be provided if a task definition ARN is not present on the task run request. (type=value_error)

The error message you're encountering suggests that you're using Prefect's AWS ECS integration, either in Prefect 2.x or 3.x, and it requires a task definition to be specified if a task definition ARN is not given in the task run request. In AWS ECS, a task definition is a blueprint for your application, describing one or more containers to form your tasks. The error indicates that Prefect needs this configuration to launch tasks correctly but doesn't have the necessary information. Here’s what you can do to resolve this: 1. Specify a Task Definition ARN: You can provide a specific task definition ARN in your flow's configuration, so Prefect knows exactly which ECS task definition to use. 2. Define Task Details in the Work Pool: If you're configuring the ECS work pool within Prefect, make sure to specify all required details such as CPU, memory, and any other necessary fields. This will help Prefect generate a task definition if one isn’t provided. For detailed guidance, it's often helpful to refer directly to Prefect's documentation on ECS integration. Check out the Prefect documentation on using ECS with Prefect for more specific setup steps. Remember, it's all about making sure Prefect knows how to handle your ECS tasks—think of it as setting up instructions for a slightly paranoid (but very efficient) virtual assistant! For further details, you can also look into these resources: - Prefect's AWS ECS guide: ECS Guide Prefect 2.x & ECS Guide Prefect 3.x. If there are any specific configurations or settings you're unsure of, let me know!

@Marvin what type of templating does prefect support? seems like it can't handle this for the worker template

"{{ cpu | default ${local.env_defaults.cpu} }}"

It seems like you're encountering some challenges with templating in Prefect. Prefect supports templating using double curly braces

{{ }}

, similar to Jinja, but there are rules and limitations to how variables are interpolated: 1. Template Usage and Rules: Prefect allows the use of template variables in configurations, and these variables can replace entire keys or be interpolated into string values. If a template variable is the sole value and isn't provided, the key will be removed from the configuration. More details on how this works can be found in Prefect's documentation for worker configurations: Developing a New Worker Type. 2. Prefect 3.x Templating: Values within your

prefect.yaml

can reference dynamic values in several ways, using the

{{ }}

format for fields and allowing block references. This includes step outputs and Prefect blocks (e.g., sensitive information stored in Prefect blocks). See more about Prefect YAML and workers here: Prefect 3.x YAML Templating. 3. Limitations: The expression

{{ cpu | default ${local.env_defaults.cpu} }}

suggests a mix of Jinja-like syntax and possibly shell/environment variable syntax which might not directly work unless explicitly supported. Prefect's templating might not support such complex logic directly within templates. Consider simplifying the template expression or ensuring the value is set elsewhere before using it in Prefect's templating. If you have logic like

default

, indeed trying to handle it outside the template and passing pre-evaluated values might be necessary. So while Prefect supports some degree of dynamic templating, the full Jinja templating engine with all its filters and defaults isn't directly supported in the same way by Prefect. You might need a simple value interpolation strategy instead. For further details, refer to these resources: - Prefect 2.x Worker Type Development - Prefect 3.x Deployment Concepts If you're still puzzled, engaging the Prefect community or checking their GitHub issues might provide some real-world insights or code examples!

@Marvin i want to give a default to {{ memory }} while allowing a it to be overridden

When working with Prefect, especially in setting configurations like memory defaults for workers, you can achieve this with the template approach where a default value is established in your configuration and allows for overrides. While Prefect's templating doesn't directly support logic like Jinja's defaults within the placeholder itself, you can handle it by structuring your configuration sensibly. Here's a general strategy you can follow: 1. Define a Default in Your Configuration: - Set a default value for memory directly within your configuration structure. - If you're using a YAML configuration (like

prefect.yaml

), specify a baseline memory value for your worker type. 2. Allow Override via Environment or Parameters: - You can use environment variables or parameters when deploying or running the flow to override this default. - Prefect allows referencing these variables, so you can define them externally depending on your environment or setup. 3. Use Conditionals Elsewhere: - If you need more complex logic or decide during run-time, handle this logic within the actual script or logic that sets up the flow run, not directly in the templating feature. Here's a simple illustrative example:

yaml
# Define a default for memory in your YAML config
memory: "{{ env.MEMORY | default('512Mi') }}"

When deploying or running your Prefect flow, you can specify the

MEMORY

environment variable to override the default

512Mi

. Additionally, you might use Prefect Blocks if you're working in Prefect 3.x to handle broader configuration management. They enable storing and accessing configuration data which can be used to parameterize your flows. For more specific Prefect 3.x syntax, where variables set in Prefect Blocks could be employed, you can refer to the Prefect YAML Templating documentation. With this approach, you get the flexibility of defaults and easy overrides through your execution environment or deployment scripts. Do reach out if you need guidance on where to slot this logic based on your deployment strategy!

@Marvin this is on the json for the worker

If you're dealing with JSON configurations for Prefect workers, you'll need to manage the default and override system a bit differently as JSON itself doesn't support templating or default value logic directly within its structure. Here's how you might approach it: 1. Set a Default Value in Your JSON: - Directly specify a default value within the JSON configuration for memory. 2. Use Environment Variable Substitution: - Use environment variable substitution when the JSON is processed to allow for overrides. This means the actual value for memory can be dynamically set based on an environment variable. 3. Externalize the Logic: - Given the limitations, consider handling default logic in your code before setting up the JSON, or use a script to preprocess the JSON file and replace or set values accordingly. An example JSON setting with environmental substitution might look like this:

json
{
    "memory": "${MEMORY:-512Mi}"
}

But JSON doesn't natively support this syntax. Instead, you would need a pre-processing step in your deployment script:

python
import os

# Example setup script in Python
worker_config = {
    "memory": os.environ.get("MEMORY", "512Mi")
}

# Convert this into JSON or pass it directly to wherever it's needed

This script will set the

memory

key to the value of the

MEMORY

environment variable if it's set, or default to

512Mi

otherwise. You can integrate such a script as part of your deployment pipeline to ensure your JSON is configured correctly before being used by Prefect. If your system supports Jinja templates or another templating engine, you could preprocess the JSON through these to achieve variable substitution, but that would be outside the JSON file and managed by the templating engine or a script. Feel free to ask if you need more help adjusting this to your particular setup!