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Joshua Caskie

06/25/2024, 5:59 PM

@Marvin What's the best way to handle environment variables in flows?

Marvin

06/25/2024, 6:00 PM

To handle environment variables in your Prefect flows, here are some methods and recommendations sourced from the Prefect documentation and examples: ### Overriding Job Variables One common pattern is to override job variables in the deployment methods. - Define environment variables in the

prefect.yaml

file or override them during the

.deploy()

method call. - These environment variables can be set in the runtime environment of the flow run. For example:

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yaml
env:
  EXECUTION_ENV: staging
  MY_NOT_SO_SECRET_CONFIG: plumbus

Source: Prefect Documentation: Overriding Work Pool Job Variables ### Using Prefect Profiles You can define a profile with specific environment settings and switch between profiles as needed. - Set the environment variable

PREFECT_PROFILE

to the name of the desired profile:

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bash
  export PREFECT_PROFILE=foo

- Alternatively, specify it in the CLI command for one-time usage:

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bash
  prefect --profile "foo" flow-run ls

Environment variables set this way will take precedence over values in the profile settings. Source: Prefect Documentation: Settings ### Code Example Here is a simple code example on how to call any Python code, including Prefect tasks or flows, with environment variables:

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python
from prefect import flow

@flow(log_prints=True)
def my_workflow():
    print("I can call any python code here, including prefect tasks or flows")

if __name__ == "__main__":
    my_workflow()  # call it like a normal python function

    # or serve it as a long-lived process
    # my_workflow.serve("my-deployment-name")

You can find more examples and details in the provided code examples. --- These methods should help you manage environment variables effectively in your Prefect flows. Let me know if you need further assistance.

Joshua Caskie

06/25/2024, 7:39 PM

@Marvin How do you set environment variables in deployments, using the .deploy() method?

Marvin

06/25/2024, 7:39 PM

When deploying a flow using the

.deploy()

method, you can set environment variables using the

job_variables

parameter in your deployment definition. Here’s a step-by-step guide on how to do it: ### Example Using

job_variables

1. Define Environment Variables in the Deployment: You can add a

job_variables

section in your deployment definition (usually in your

prefect.yaml

file or within your script). Here’s an example of what that might look like in your `prefect.yaml`:

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yaml
   deployments:
   - name: demo-deployment
     entrypoint: demo_project/demo_flow.py:some_work
     work_pool:
       name: local
     job_variables:
       env:
         EXECUTION_ENVIRONMENT: staging
         MY_NOT_SO_SECRET_CONFIG: plumbus
     schedule: null

2. Deploy the Flow: Run the following command to deploy the flow with these job variables:

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bash
   prefect deploy -n demo-deployment

3. Deploy Using
.deploy()
Method: Alternatively, you can set these variables directly in your deployment script using the

.deploy()

method.

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python
   from prefect.deployments import Deployment
   from demo_project.demo_flow import some_work

   Deployment(
       name="demo-deployment",
       flow_location="demo_project/demo_flow.py",
       work_pool_name="local",
       job_variables={
           "env": {
               "EXECUTION_ENVIRONMENT": "staging",
               "MY_NOT_SO_SECRET_CONFIG": "plumbus"
           }
       }
   ).apply()

### Tips - Templating Existing Environment Variables: If you want to use environment variables that are already set in your local environment, you can template these in your deployment definition as follows:

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yaml
  job_variables:
    env:
      EXECUTION_ENVIRONMENT: "{{ execution_env }}"
      MY_NOT_SO_SECRET_CONFIG: "{{ not_so_secret_config }}"

Then, set the variables in your local environment before deploying:

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bash
  export execution_env=staging
  export not_so_secret_config=plumbus
  prefect deploy -n demo-deployment

### Documentation Links - Overriding Work Pool Job Variables - Prefect Deploy Guide These steps should allow you to effectively set and manage environment variables in your Prefect deployments. If you need further assistance, feel free to ask.

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