@Marvin how can I make a task only use the cache on flow retries and not in new flow runs

To ensure that a task only uses the cache on flow retries and not in new flow runs, you can configure the

cache_key_fn

to be dependent on the flow run ID. This ensures that the cache is only valid within the same flow run. Here's a basic example: 1. Define a caching mechanism for the task that includes the flow run ID. 2. Set the cache key to include identifiers that will differentiate between different flow runs but be consistent across retries.

python
from prefect import flow, task, get_run_logger
from prefect.context import FlowRunContext

def cache_key_with_flow_run_id(task, params):
    # Fetch the current flow run context
    flow_run_ctx = FlowRunContext.get()
    # Return a composite key with the flow run ID and task parameters
    return f"{flow_run_ctx.flow_run.name}:{str(params)}"

@task(cache_key_fn=cache_key_with_flow_run_id)
def my_task(x):
    logger = get_run_logger()
    <http://logger.info|logger.info>(f"Running task with value: {x}")
    return x * 2

@flow(retries=1)
def my_flow():
    result = my_task(10)

if __name__ == "__main__":
    my_flow()

### Explanation: - The function

cache_key_with_flow_run_id

generates a cache key that includes the flow run ID, making the cache specific to the flow run and its retries. - The

cache_key_fn

parameter in the

@task

decorator ensures this custom cache key function is used. ### References: - Prefect Documentation on Task Caching - GitHub Issue on Task Refresh Cache Behavior This approach will ensure tasks use the cache within the same flow run, including retries, but not across different flow runs.

@Marvin this worked but now I have another problem: I am doing my testing using pytest, and my tests are failing with the following errors: ERROR collecting backend/workflows_2/tests/test_search_tasks.py ERROR backend/workflows_2/tests/test_search_tasks.py - ValueError: Unable to find block document named s3-flows-results-path for block type secret How can I fix this?

To resolve the error regarding the missing block document in your pytest tests, ensure that the block document named

"s3-flows-results-path"

for block type

"secret"

is correctly created and available in your Prefect environment. Here's a step-by-step process to address this: 1. Check if the Block Document Exists: Ensure that the block

"s3-flows-results-path"

of type

"secret"

exists. 2. Create the Block if it Doesn't Exist: If the block does not exist, you can create it programmatically or through the Prefect UI.

python
   from prefect.blocks.system import Secret

   # Define the secret block
   secret_value = "your_secret_value"
   secret_block = Secret(value=secret_value)

   # Save the block with the name "s3-flows-results-path"
   secret_block.save(name="s3-flows-results-path")

3. Ensure Your Test Environment is Correctly Configured: Make sure your test environment has access to the Prefect blocks configured in your Prefect Cloud or server. 4. Mock the Block for Testing: When running tests, you can mock the block to ensure that your tests do not depend on the actual Prefect environment. Here’s an example using `unittest.mock`:

python
   from unittest.mock import patch
   import pytest
   from prefect import context

   @pytest.fixture(autouse=True)
   def mock_prefect_blocks():
       with patch.dict(context.Block, {"s3-flows-results-path": Secret(value="test_secret_value")}):
           yield

Here's a more complete example of what the test fixture might look like:

python
import pytest
from unittest.mock import patch
from prefect.blocks.system import Secret

@pytest.fixture(autouse=True)
def mock_prefect_blocks():
    secret_mock = Secret(value="test_secret_value")
    with patch("prefect.blocks.get_block", return_value=secret_mock):
        yield

def test_your_prefect_flow():
    # Add your test code here
    pass

This mock ensures that during the test run, any attempt to retrieve the

"s3-flows-results-path"

block will return the mocked secret value. ### References: - Prefect Documentation on Blocks - Concrete Example for Mocking in `pytest` By following these steps, you should be able to run your tests without encountering the block document error.