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<@ULVA73B9P> How to set environment variables duri...
# marvin-in-the-wild
j
@Marvin How to set environment variables during a flow run?
m
To set environment variables during a Prefect flow run, you can use the 
job_variables
parameter when deploying your flow. Here’s a snippet that illustrates how to achieve this:
Copy code
from prefect import flow

@flow
def my_flow():
    # Your flow logic here
    pass

deployment = my_flow.deploy(
    name="my-deployment",
    work_pool_name="local",  # Specify the work pool name
    job_variables={
        "env": {
            "ENV_VAR_ONE": "value_one",
            "ENV_VAR_TWO": "value_two"
        }
    }
)
You can find more details in Prefect's documentation on overriding job variables. Additionally, you can set the Prefect profile environment variable for specific use cases as described in the Prefect Settings Guide. For any issues or detailed use cases, you can also refer to discussions and issues on GitHub.
j
@Marvin Can i do 
os.environ["VAR"]
during a flow run to set a variable?
m
Using 
os.environ["VAR"]
to set an environment variable during a flow run is generally not advisable in Prefect flows. This is because the environment variables set in this way will only affect the process running the flow and won't propagate to the task environments managed by Prefect workers or agents. Instead, you should use job variables or set environment variables within the deployment configuration itself, as described in the guide on overriding job variables. For example, you can pass environment variables when deploying your flow:
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from prefect import flow

@flow
def my_flow():
    import os
    print(f"MY_VAR is {os.environ.get('MY_VAR')}")

deployment = my_flow.deploy(
    name="my-deployment",
    work_pool_name="local",
    job_variables={
        "env": {
            "MY_VAR": "my_value"
        }
    }
)
This ensures that the environment variables are correctly set in the context where the flow tasks are executed.
j
@Marvin how to set secret job variables so they are kept secret?
m
To set secret job variables while keeping them secure during a flow run in Prefect, you can use Prefect's secret management functionality through the 
prefect.blocks.secret.Secret
class. Here's how you can do it: 1. Create a Secret Block: First, create a secret block in Prefect. 2. Use the Secret in Deployment: Refer to this secret in your 
prefect.yaml
or deployment script. Below is an example showing how to achieve this:
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python
from prefect.blocks.system import Secret
from prefect import flow, task

# Create a secret block
Secret(name="my-secret", secret="super-secret-value").save("my-secret-block")

@task
def use_secret():
    secret_value = Secret.load("my-secret-block").get()
    print(f"The secret value is: {secret_value}")

@flow
def my_flow():
    use_secret()

my_flow.deploy(
    name="secure-flow-deployment",
    work_pool_name="local",
    job_variables={
        "env": {
            "SECRET_VAR": "{{ prefect.blocks.secret.my-secret-block }}"
        }
    }
)
### Important Links: - Overriding Job Variables - Handling Secrets in Prefect #### Note: Be cautious as there may be reported issues where secrets show up under the deployment configuration in the UI, so ensure your setup masks these appropriately.
j
@Marvin How to do this with a YAML and a SnowflakeCredentials block?
m
Here’s how you can set up a 
SnowflakeCredentials
block in YAML for a Prefect deployment: 1. Create a SnowflakeCredentials Block in Python: First, create a SnowflakeCredentials block and save it:
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python
   from prefect_snowflake import SnowflakeCredentials

   credentials = SnowflakeCredentials(
       account="<http://your-account.us-east-1.snowflakecomputing.com|your-account.us-east-1.snowflakecomputing.com>",
       user="your-username",
       password="your-password"   # Ideally use a secret management tool for the password
   )
   credentials.save("my-snowflake-credentials")
2. Use the SnowflakeCredentials Block in 
prefect.yaml
: Create a 
prefect.yaml
file that references this block.
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yaml
   name: my-snowflake-deployment
   version: 1
   work_pool:
     name: your-work-pool
     job_variables:
       env:
         SNOWFLAKE_CREDENTIALS: "{{ prefect.blocks.secret.my-snowflake-credentials }}"

   deployments:
   - name: my-snowflake-deployment
     entrypoint: path/to/your/flow.py:your_flow_function
     work_pool:
       name: your-work-pool
     job_variables:
       env:
         SNOWFLAKE_CREDENTIALS: "{{ prefect.blocks.secret.my-snowflake-credentials }}"
In this configuration, 
SNOWFLAKE_CREDENTIALS
will reference the 
my-snowflake-credentials
block, keeping the credentials secure and not exposing them directly in your YAML file. Important Links: - Using Snowflake with Prefect - Managing Secrets in Prefect Make sure to replace placeholders with your actual values. This approach ensures that your credentials remain secure and are handled properly by Prefect during deployment.
j
@Marvin How would SNOWFLAKE_CREDENTIALS be referenced if set in the job variables via YAML? Is it a Block, or is it a JSON?
m
When referencing a 
SnowflakeCredentials
block in job variables via YAML, the block is referenced as a Prefect block type within the job variables. It uses a special syntax to reference the block by its name. Here’s an example of how to set and reference the 
SnowflakeCredentials
block in your 
prefect.yaml
file: 1. Create and Save a SnowflakeCredentials Block:
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python
   from prefect_snowflake import SnowflakeCredentials

   # Replace placeholders with actual values
   credentials = SnowflakeCredentials(
       account="<http://your-account.us-east-1.snowflakecomputing.com|your-account.us-east-1.snowflakecomputing.com>",
       user="your-username",
       password="your-password"  # Use a secret management tool ideally
   )
   credentials.save("my-snowflake-credentials")
2. Configure the YAML for Deployment:
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yaml
   name: my-snowflake-deployment
   version: 1
   work_pool:
     name: your-work-pool
     job_variables:
       env:
         SNOWFLAKE_CREDENTIALS: "{{ prefect.blocks.snowflake-credentials.my-snowflake-credentials }}"

   deployments:
   - name: my-snowflake-deployment
     entrypoint: path/to/your/flow.py:your_flow_function
     work_pool:
       name: your-work-pool
     job_variables:
       env:
         SNOWFLAKE_CREDENTIALS: "{{ prefect.blocks.snowflake-credentials.my-snowflake-credentials }}"
In this YAML configuration, 
SNOWFLAKE_CREDENTIALS
is set to reference the 
my-snowflake-credentials
block. The block syntax 
{{ prefect.blocks.snowflake-credentials.my-snowflake-credentials }}
tells Prefect to fetch the credentials securely stored in the specified block. Important Links: - Using Snowflake with Prefect - Handling Secrets in Prefect Make sure to replace placeholders with actual values. This approach ensures that your credentials remain secure and are appropriately referenced in your deployment configuration.
j
When the YAML is like yaml name: my-snowflake-deployment version: 1 work_pool: name: your-work-pool job_variables: env: SNOWFLAKE_CREDENTIALS: "{{ prefect.blocks.snowflake-credentials.my-snowflake-credentials }}" deployments: - name: my-snowflake-deployment entrypoint: path/to/your/flow.py:your_flow_function work_pool: name: your-work-pool job_variables: env: SNOWFLAKE_CREDENTIALS: "{{ prefect.blocks.snowflake-credentials.my-snowflake-credentials }}" how do I reference SNOWFLAKE_CREDENTIALS in python?
k
hmm the credentials block has multiple fields right?
👍 1
but env vars need to be just strings
j
I'm successfully loading the SnowflakeCredentials block during the flow run, but I need to set environment variables for the run to use.
But that doesn't work inside the flow using os.environ
So now looking at how to set them prior to the run via the job_variables section, just looking to confirm how to now load the 
SNOWFLAKE_CREDENTIALS
in code
k
is it not possible to instantiate a snowflake client off of the credentials block?
why is the env var a requirement?
j
Our dbt profiles.yml looks for environment variables
Looking to keep that consistent with our setup, and set them prior to dbt run
k
ahhh understood. so which specific value do you need? is it just like, a secret key you need as an env var?
j
Yep. Specifically it's for our snowflake credentials
So I have them stored in a block fine, and now just trying to have them dynamically work
k
maybe more simply then, store it in a secret block? then reference that block in your yaml, setting it as the value for your 
SNOWFLAKE_CREDENTIALS
key in your 
env
job var?
then when your flow runs that env var will just be there
j
Definitely could work, but hoping to solution this out if possible where we use the right block type
k
what other use would the snowflake blocks serve if you're using dbt?
j
Direct Snowflake connections via connector blocks
k
so you're looking to do both
I think you can access specific fields from a block in the template reference too?
{{ prefect.blocks.snowflake-credentials.my-snowflake-credentials.secret_key }} or whatever the field name is
🙌 1
maybe?
j
That was my next guess, i'll check into that and get back
👍 1
k
let me know if it works
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